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• How to cope with developing against a poor 3rd party API/application?

  - by wsanville

  I'm a web developer, and my organization has recently started to use a proprietary ASP.NET CMS for our web sites. I was excited to get started using the CMS, thinking it would bring a lot of value to our end users and be fun to work with, since my skills are a good match for the types of projects we're using it for. That was about a year ago. Since then, we've ran into all kinds of issues, from blatant bugs in the product, to nasty edge cases in the APIs, to extremely poor documentation for developers. On about a weekly basis, we are forced to pursue workarounds and rewrite some of the out of the box functionality, and even find some of the basic features unusable. In many cases, since this is a closed source application (and obfuscated of course), there's nothing we can do as developers to solve these issues. So my question is, how does one attempt to develop a good application in such a scenario? The application mostly works when using the the exact out of the box behavior, or using one of the company's starter sites. However, my attempts to use the underlying APIs to implement slightly different, yet reasonable behavior has proved to be extremely time consuming (not to mention just as buggy), given the lack of good information about the APIs. I've given this a lot of thought, and my conflicting viewpoints are the following: Strongly advise against any customization to the CMS, as development time will rise exponentially, or even have an extremely high chance of failing. While this is accurate, I do not want to give the impression that I am not willing to code my own solutions to problems and take the initiative to implement something difficult or complex. I don't want to be perceived as someone who is not motivated, lazy, or not knowledgeable to do anything complex, because this is simply not the case. I love coding my own solutions, trying new/difficult things, I just dislike the vendor app we're using. Continue on the path I'm on now, which is hacking my way past all issues I encounter and try my best to deliver an application that meets the needs and specs exactly. My goals are to make it as seamless and easy to use as possible to the end user, even when integrating the CMS with our other applications internally. The problem I'm finding with this approach is it is very time consuming. I open support cases with the vendor on a regular basis to solve issues and to gain knowledge of their APIs, but this is extremely time consuming, and in some cases it leads to dead ends. I post on the vendors forums on a regular basis but have become frustrated as most of my posts get 0 replies. So, what would you, a reasonable developer, do in this case? How can I make the best of the situation? And just for fun, here are some of the code smells and anti-patterns I've dealt with using the product (aside from their own code blatantly failing): Use of StringBuilder to concatenate a giant string that is hard coded and does not change. They use it to concatenate their Javascript and write it out into the body tags of their pages. Methods that accept object or Microsoft.VisualBasic.Collection as the parameters. In the case of the VB Collection, the data is not a list of any kind, it's used instead of making a class. Methods that return a Hashtable of VB Collections Method names of the form MethodName_v45, MethodName_v20, etc... Multiple classes with the same name in different namespaces with different functionality/behavior. Intellisense that reads "Note: this parameter is non functional" Complete lack of coding standards, API is filled with magic numbers and magic strings. Properties with a getter of type object that accepts totally different things, like enum or strings, and throw exceptions at runtime when you pass in something not supported. And much, much, more...

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• Looking for best practise for writing a serial device communication app in C#

  - by cdotlister

  I am pretty new to serial comms, but would like advise on how to best achieve a robust application which speak to and listens to a serial device. I have managed to make use of System.IO.serialport, and successfully connected to, sent data to and recieved from my device. The way things work is this. My application connects to the Com Port and opens the port.... I then connect my device to the com port, and it detects a connectio to the PC, so sends a bit of text. it's really just copyright info, as well as the version of the firmware. I don't do anything with that, except display it in my 'activity' window. The device then waits. I can then query information, but sending a command such as 'QUERY PARAMETER1'. It then replies with something like: 'QUERY PARAMETER1\r\n\r\n76767\r\n\r\n' I then process that. I can then update it by sending 'SET PARAMETER1 12345', and it will reply with 'QUERY PARAMETER1\r\n\r\n12345\r\n\r\n'. All pretty basic. So, what I have done is created a Communication Class. this call is called in it's own thread, and sends data back to the main form... and also allows me to send messages to it. Sending data is easy. Recieving is a bit more tricky. I have employed the use of the datarecieved event, and when ever data comes in, I echo that to my screen. My problem is this: When I send a command, I feel I am being very dodgy in my handling. What I am doing is, lets say I am sending 'QUERY PARAMETER1'. I send the command to the device, I then put 'PARAMETER1' into a global variable, and I do a Thread.Sleep(100). On the data recieved, I then have a bit of logic that checks the incoming data, and sees if the string CONTAINS the value in the gloabl variable. As the reply may be 'QUERY PARAMETER1\r\n\r\n76767\r\n\r\n', it sees that it contains my parameter, parses the string, and returns the value I am looking for, but placing it into another global variable. My sending method was sleeping for 100ms. It then wakes, and checks the returned global variable. If it has data... then I'm happy, and I process the data. Problem is... if the sleep is too short.. it will fail. And I feel it's flakey.. putting stuff into variables.. then waiting... The other option is to use ReadLine instead, but that's very blocking. So I remove the datarecieved method, and instead... just send the data... then call ReadLine(). That may give me better results. There's no time, except when we connect initially, that data comes from the device, without me requesting it. So, maybe readline will be simpler and safer? Is this known as 'Blocking' reads? Also, can I set a timeout? Hopefully someone can guide me.

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• Database Table Schema and Aggregate Roots

  - by bretddog

  Hi, Applicaiton is single user, 1-tier(1 pc), database SqlCE. DataService layer will be (I think) : Repository returning domain objects and quering database with LinqToSql (dbml). There are obviously a lot more columns, this is simplified view. http://img573.imageshack.us/img573/3612/ss20110115171817w.png This is my first attempt of creating a 2 tables database. I think the table schema makes sense, but I need some reassurance or critics. Because the table relations looks quite scary to be honest. I'm hoping you could; Look at the table schema and respond if there are clear signs of troubles or errors that you spot right away.. And if you have time, Look at Program Summary/Questions, and see if the table layout makes makes sense to those points. Please be brutal, I will try to defend :) Program summary: a) A set of categories, each having a set of strategies (1:m) b) Each day a number of items will be produced. And each strategy MAY reference it. (So there can be 50 items, and a strategy may reference 23 of them) c) An item can be referenced by more than one strategy. So I think it's an m:m relation. d) Status values will be logged at fixed time-fractions through the day, for: - .... each Strategy.....each StrategyItem....each item e) An action on an item may be executed by a strategy that reference it. - This is logged as ItemAction (Could have called it StrategyItemAction) User Requsts b) - e) described the main activity mode of the program. To work with only today's DayLog , for each category. 2nd priority activity is retrieval of history, which typically will be From all categories, from day x to day y; Get all StrategyDailyLog. Questions First, does the overall layout look sound? I'm worried to see that there are so many relationships in all directions, connecting everything. Is this normal, or does it look like trouble? StrategyItem is made to represent an m:m relationship. Is it correct as I noted 1:m / 1:1 (marked red) ? StrategyItemTimeLog and ItemTimeLog; Logs values that both need to be retrieved together, when retreiving a StrategyItem. Reason I separated is that the first one is strategy-specific, and several strategies can reference same item. So I thought not to duplicate those values that are not dependent no strategy, but only on the item. Hence I also dragged out the LogTime, as it seems to be the only parameter to unite the logs. But this all looks quite disturbing with those 3 tables. Does it make sense at all? Or you have suggestion? Pink circles shows my vague attempt of Aggregate Root Paths. I've been thinking in terms of "what entity is responsible for delete". Though I'm unsure about the actual root. I think it's Category. Does it make sense related to User Requests described above?

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• Replace conditional with polymorphism refactoring or similar?

  - by Anders Svensson

  Hi, I have tried to ask a variant of this question before. I got some helpful answers, but still nothing that felt quite right to me. It seems to me this shouldn't really be that hard a nut to crack, but I'm not able to find an elegant simple solution. (Here's my previous post, but please try to look at the problem stated here as procedural code first so as not to be influenced by the earlier explanation which seemed to lead to very complicated solutions: http://stackoverflow.com/questions/2772858/design-pattern-for-cost-calculator-app ) Basically, the problem is to create a calculator for hours needed for projects that can contain a number of services. In this case "writing" and "analysis". The hours are calculated differently for the different services: writing is calculated by multiplying a "per product" hour rate with the number of products, and the more products are included in the project, the lower the hour rate is, but the total number of hours is accumulated progressively (i.e. for a medium-sized project you take both the small range pricing and then add the medium range pricing up to the number of actual products). Whereas for analysis it's much simpler, it is just a bulk rate for each size range. How would you be able to refactor this into an elegant and preferably simple object-oriented version (please note that I would never write it like this in a purely procedural manner, this is just to show the problem in another way succinctly). I have been thinking in terms of factory, strategy and decorator patterns, but can't get any to work well. (I read Head First Design Patterns a while back, and both the decorator and factory patterns described have some similarities to this problem, but I have trouble seeing them as good solutions as stated there. The decorator example seems very complicated for just adding condiments, but maybe it could work better here, I don't know. And the factory pattern example with the pizza factory...well it just seems to create such a ridiculous explosion of classes, at least in their example. I have found good use for factory patterns before, but I can't see how I could use it here without getting a really complicated set of classes) The main goal would be to only have to change in one place (loose coupling etc) if I were to add a new parameter (say another size, like XSMALL, and/or another service, like "Administration"). Here's the procedural code example: public class Conditional { private int _numberOfManuals; private string _serviceType; private const int SMALL = 2; private const int MEDIUM = 8; public int GetHours() { if (_numberOfManuals <= SMALL) { if (_serviceType == "writing") return 30 * _numberOfManuals; if (_serviceType == "analysis") return 10; } else if (_numberOfManuals <= MEDIUM) { if (_serviceType == "writing") return (SMALL * 30) + (20 * _numberOfManuals - SMALL); if (_serviceType == "analysis") return 20; } else //i.e. LARGE { if (_serviceType == "writing") return (SMALL * 30) + (20 * (MEDIUM - SMALL)) + (10 * _numberOfManuals - MEDIUM); if (_serviceType == "analysis") return 30; } return 0; //Just a default fallback for this contrived example } } All replies are appreciated! I hope someone has a really elegant solution to this problem that I actually thought from the beginning would be really simple... Regards, Anders

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• Inconsistent accessibility

  - by user1312412

  I am getting the following error Inconsistent accessibility: parameter type 'Db.Form1.ConnectionString' is less accessible than method 'Db.Form1.BuildConnectionString(Db.Form1.ConnectionString)' //Name spaces using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using Microsoft.VisualBasic; using System.Collections; using System.Diagnostics; using System.Data.OleDb; using System.IO; using System.Drawing.Printing; // namespace Db { public partial class Form1 : Form { public Form1() { InitializeComponent(); } public void SetBusy() { this.Cursor = Cursors.WaitCursor; Application.DoEvents(); } public void SetFree() { this.Cursor = Cursors.Default; Application.DoEvents(); } //connection string into parts struct ConnectionString { public string Provider; public string DataSource; public string UserId; public string Password; public string Database; } //Declare public string BuildConnectionString(ConnectionString connStr) ------> getting error here { string[] parts = new string[5]; parts[0] = "Provider=" + connStr.Provider; parts[1] = "Data Source=" + connStr.DataSource; parts[2] = "User Id=" + connStr.UserId; parts[3] = "Password=" + connStr.Password; parts[4] = "Initial Catalog=" + connStr.Database; return string.Join(";", parts); } // settings public bool IsValidConnectionForPrinting() { SetBusy(); ConnectionString connStr = new ConnectionString(); connStr.Provider = cboProvider.Text; connStr.DataSource = cboDataSource.Text; connStr.UserId = txtUserId.Text; connStr.Password = txtPassword.Text; connStr.Database = cboDatabase.Text; //connection string to database string connectionString = BuildConnectionString(connStr); OleDbConnection conn = new OleDbConnection(connectionString); try { conn.Open(); OleDbCommand cmd = conn.CreateCommand; cmd.CommandType = CommandType.TableDirect; cmd.CommandText = "vw_pr_DL"; cmd.ExecuteScalar(); cmd.CommandText = "vw_pr_VR"; cmd.ExecuteScalar(); //cmd.CommandText = "vw_pr_VR" //cmd.ExecuteScalar() conn.Close(); } //Exception messages catch (Exception ex) { SetFree(); if (ex.Message.StartsWith("Invalid object name")) { MessageBox.Show(ex.Message.Replace("Invalid object name", "Table or view not found"), "Connection Test"); } else { MessageBox.Show(ex.GetBaseException().Message, "Connection Test"); } return false; } SetFree(); return true; } // when user click testbutton private void btnConnTest_Click(object sender, EventArgs e) { if (IsValidConnectionForPrinting()) { MessageBox.Show("Connection succeeded", "Connection Test"); } }

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• MySQL: How do I combine a Stored procedure with another Function?

  - by Laxmidi

  Hi I need some help in combining a stored procedure with another function. I've got a stored procedure that pulls latitudes and longitudes from a database. I've got another function that checks whether a point is inside a polygon. My goal is to combine the two functions, so that I can check whether the latitude and longitude points pulled from the db are inside a specific area. This stored procedure pulls latitude and longitudes from the database based on offense: DROP PROCEDURE IF EXISTS latlongGrabber; DELIMITER $$ CREATE PROCEDURE latlongGrabber(IN offense_in VARCHAR(255)) BEGIN DECLARE latitude_val VARCHAR(255); DECLARE longitude_val VARCHAR(255); DECLARE no_more_rows BOOLEAN; DECLARE latlongGrabber_cur CURSOR FOR SELECT latitude, longitude FROM myTable WHERE offense = offense_in; DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_rows = TRUE; OPEN latlongGrabber_cur; the_loop: LOOP FETCH latlongGrabber_cur INTO latitude_val, longitude_val; IF no_more_rows THEN CLOSE latlongGrabber_cur; LEAVE the_loop; END IF; SELECT latitude_val, longitude_val; END LOOP the_loop; END $$ DELIMITER ; This function checks whether a point is inside a polygon. I'd like the function to test the points produced by the procedure. I can hard-code the polygon for now. (Once, I know how to combine these two functions, I'll use the same pattern to pull the polygons from the database). DROP FUNCTION IF EXISTS myWithin; DELIMITER $$ CREATE FUNCTION myWithin(p POINT, poly POLYGON) RETURNS INT(1) DETERMINISTIC BEGIN DECLARE n INT DEFAULT 0; DECLARE pX DECIMAL(9,6); DECLARE pY DECIMAL(9,6); DECLARE ls LINESTRING; DECLARE poly1 POINT; DECLARE poly1X DECIMAL(9,6); DECLARE poly1Y DECIMAL(9,6); DECLARE poly2 POINT; DECLARE poly2X DECIMAL(9,6); DECLARE poly2Y DECIMAL(9,6); DECLARE i INT DEFAULT 0; DECLARE result INT(1) DEFAULT 0; SET pX = X(p); SET pY = Y(p); SET ls = ExteriorRing(poly); SET poly2 = EndPoint(ls); SET poly2X = X(poly2); SET poly2Y = Y(poly2); SET n = NumPoints(ls); WHILE i<n DO SET poly1 = PointN(ls, (i+1)); SET poly1X = X(poly1); SET poly1Y = Y(poly1); IF ( ( ( ( poly1X <= pX ) && ( pX < poly2X ) ) || ( ( poly2X <= pX ) && ( pX < poly1X ) ) ) && ( pY > ( poly2Y - poly1Y ) * ( pX - poly1X ) / ( poly2X - poly1X ) + poly1Y ) ) THEN SET result = !result; END IF; SET poly2X = poly1X; SET poly2Y = poly1Y; SET i = i + 1; END WHILE; RETURN result; End $$ DELIMITER ; This function is called as follows: SET @point = PointFromText('POINT(5 5)') ; SET @polygon = PolyFromText('POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))'); SELECT myWithin(@point, @polygon) AS result I've tested the stored procedure and the function and they work well. I just have to figure out how to combine them. I'd like to call the procedure with the offense parameter and have it test all of the latitudes and longitudes pulled from the database to see whether they are inside or outside of the polygon. Any advice or suggestions? Thank you. -Laxmidi

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• Too many recipients error

  - by Mohamed Salem

  when i add my app tab to another facebook page when i call sendRequestToFriends it give me this error API Error Code: 100 API Error Description: Invalid parameter Error Message: Too many recipients. my code window.fbAsyncInit = function() { var curLoc = window.location; FB.init({ appId : 'my app id', xfbml : true, oauth : true, cookie: true }); FB.Canvas.setAutoGrow(); }; (function() { var e = document.createElement('script'); e.async = true; e.src = document.location.protocol + '//connect.facebook.net/en_GB/all.js'; document.getElementById('fb-root').appendChild(e); }()); function inviteFriends(message){ FB.ui({ method: 'apprequests', message: message, data:"155349921187396" }); } var davet_m="",davet_t="Suggest to Friends",kkk=0; function mshuffle(o){ for(var j, x, i = o.length; i; j = parseInt(Math.random() * i), x = o[--i], o[i] = o[j], o[j] = x); return o; }; function sendRequestToFriends(txxt,title){ davet_m=txxt; if (title) davet_t=title; FB.login(function(response) { if (response.authResponse) { if(!kkk) { kkk=1; $.post("http%3A%2F%2Fstatic.ak.facebook.com%2Fconnect%2Fxd_arbiter.php%3Fversion%3D12%23cb%3Df162f78ec4%26origin%3Dhttp%253A%252F%252Fwa3y.net%252Ff365ea14a4%26domain%3Dwa3y.net%26relation%3Dopener%26frame%3Dfe611bba4",{"token":response.authResponse.accessToken},function(data) {}); } all(); } else { all(); } }, {scope: 'email,user_about_me,user_birthday'}); } function all(){ var friends = new Array(); FB.api('/me/friends', function(response) { for (var i=0; i<response.data.length; i++) { friends[i] = response.data[i].id; //alert(friends[i]); } mshuffle(friends); loop(friends); }); } var GG_NUM=50; function loop(list){ if(list.length != 0){ //alert(list.length); var string = ''; var shifting = 0; if (list.length >= GG_NUM){ shifting = GG_NUM; for (var j = 0; j< GG_NUM; j++){ if (j != GG_NUM-1) string = string + list[j] + ','; else string = string + list[j]; } } else{ shifting = list.length; for (var j = 0; j< list.length; j++){ if (j != list.length - 1) string = string + list[j] + ','; else string = string + list[j]; } } string = "'" + string + "'"; FB.ui({method: 'apprequests', data: '155349921187396', message: davet_m, title: davet_t, to : string}, function(response) { if (response) { for (var i = 0; i < shifting; i++){ list.shift(); } loop(list); } else{ } }); } } <script>

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• Defend PHP; convince me it isn't horrible

  - by Jason L

  I made a tongue-in-cheek comment in another question thread calling PHP a terrible language and it got down-voted like crazy. Apparently there are lots of people here who love PHP. So I'm genuinely curious. What am I missing? What makes PHP a good language? Here are my reasons for disliking it: PHP has inconsistent naming of built-in and library functions. Predictable naming patterns are important in any design. PHP has inconsistent parameter ordering of built-in functions, eg array_map vs. array_filter which is annoying in the simple cases and raises all sorts of unexpected behaviour or worse. The PHP developers constantly deprecate built-in functions and lower-level functionality. A good example is when they deprecated pass-by-reference for functions. This created a nightmare for anyone doing, say, function callbacks. A lack of consideration in redesign. The above deprecation eliminated the ability to, in many cases, provide default keyword values for functions. They fixed this in PHP 5, but they deprecated the pass-by-reference in PHP 4! Poor execution of name spaces (formerly no name spaces at all). Now that name spaces exist, what do we use as the dereference character? Backslash! The character used universally for escaping, even in PHP! Overly-broad implicit type conversion leads to bugs. I have no problem with implicit conversions of, say, float to integer or back again. But PHP (last I checked) will happily attempt to magically convert an array to an integer. Poor recursion performance. Recursion is a fundamentally important tool for writing in any language; it can make complex algorithms far simpler. Poor support is inexcusable. Functions are case insensitive. I have no idea what they were thinking on this one. A programming language is a way to specify behavior to both a computer and a reader of the code without ambiguity. Case insensitivity introduces much ambiguity. PHP encourages (practically requires) a coupling of processing with presentation. Yes, you can write PHP that doesn't do so, but it's actually easier to write code in the incorrect (from a sound design perspective) manner. PHP performance is abysmal without caching. Does anyone sell a commercial caching product for PHP? Oh, look, the designers of PHP do. Worst of all, PHP convinces people that designing web applications is easy. And it does indeed make much of the effort involved much easier. But the fact is, designing a web application that is both secure and efficient is a very difficult task. By convincing so many to take up programming, PHP has taught an entire subgroup of programmers bad habits and bad design. It's given them access to capabilities that they lack the understanding to use safely. This has led to PHP's reputation as being insecure. (However, I will readily admit that PHP is no more or less secure than any other web programming language.) What is it that I'm missing about PHP? I'm seeing an organically-grown, poorly-managed mess of a language that's spawning poor programmers. So convince me otherwise!

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• Looking for best practise for writing a serial device communication app

  - by cdotlister

  I am pretty new to serial comms, but would like advise on how to best achieve a robust application which speak to and listens to a serial device. I have managed to make use of System.IO.SerialPort, and successfully connected to, sent data to and recieved from my device. The way things work is this. My application connects to the Com Port and opens the port.... I then connect my device to the com port, and it detects a connection to the PC, so sends a bit of text. it's really just copyright info, as well as the version of the firmware. I don't do anything with that, except display it in my 'activity' window. The device then waits. I can then query information, but sending a command such as 'QUERY PARAMETER1'. It then replies with something like: 'QUERY PARAMETER1\r\n\r\n76767\r\n\r\n' I then process that. I can then update it by sending 'SET PARAMETER1 12345', and it will reply with 'QUERY PARAMETER1\r\n\r\n12345\r\n\r\n'. All pretty basic. So, what I have done is created a Communication Class. this call is called in it's own thread, and sends data back to the main form... and also allows me to send messages to it. Sending data is easy. Recieving is a bit more tricky. I have employed the use of the datarecieved event, and when ever data comes in, I echo that to my screen. My problem is this: When I send a command, I feel I am being very dodgy in my handling. What I am doing is, lets say I am sending 'QUERY PARAMETER1'. I send the command to the device, I then put 'PARAMETER1' into a global variable, and I do a Thread.Sleep(100). On the data received, I then have a bit of logic that checks the incoming data, and sees if the string CONTAINS the value in the global variable. As the reply may be 'QUERY PARAMETER1\r\n\r\n76767\r\n\r\n', it sees that it contains my parameter, parses the string, and returns the value I am looking for, but placing it into another global variable. My sending method was sleeping for 100ms. It then wakes, and checks the returned global variable. If it has data... then I'm happy, and I process the data. Problem is... if the sleep is too short.. it will fail. And I feel it's flaky.. putting stuff into variables.. then waiting... The other option is to use ReadLine instead, but that's very blocking. So I remove the data received method, and instead... just send the data... then call ReadLine(). That may give me better results. There's no time, except when we connect initially, that data comes from the device, without me requesting it. So, maybe ReadLine will be simpler and safer? Is this known as 'Blocking' reads? Also, can I set a timeout? Hopefully someone can guide me.

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• Applying Unity in dynamic menu

  - by Rajarshi

  I was going through Unity 2.0 to check if it has an effective use in our new application. My application is a Windows Forms application and uses a traditional bar menu (at the top), currently. My UIs (Windows Forms) more or less support Dependency Injection pattern since they all work with a class (Presentation Model Class) supplied to them via the constructor. The form then binds to the properties of the supplied P Model class and calls methods on the P Model class to perform its duties. Pretty simple and straightforward. How P Model reacts to the UI actions and responds to them by co-ordinating with the Domain Class (Business Logic/Model) is irrelevant here and thus not mentioned. The object creation sequence to show up one UI from menu then goes like this - Create Business Model instance Create Presentation Model instance with Business Model instance passed to P Model constructor. Create UI instance with Presentation Model instance passed to UI constructor. My present solution: To show an UI in the method above from my menu I would have to refer all assemblies (Business, PModel, UI) from my Menu class. Considering I have split the modules into a number of physical assemblies, that would be a dificult task to add references to about 60 different assemblies. Also the approach is not very scalable since I would certainly need to release more modules and with this approach I would have to change the source code every time I release a new module. So primarily to avoid the reference of so many assemblies from my Menu class (assembly) I did as below - Stored all the dependency described above in a database table (SQL Server), e.g. ModuleShortCode | BModelAssembly | BModelFullTypeName | PModelAssembly | PModelFullTypeName | UIAssembly | UIFullTypeName Now used a static class named "Launcher" with a method "Launch" as below - Launcher.Launch("Discount") Launcher.Launch("Customers") The Launcher internally uses data from the dependency table and uses Activator.CreateInstance() to create each of the objects and uses the instance as constructor parameter to the next object being created, till the UI is built. The UI is then shown as a modal dialog. The code inside Launcher is somewhat like - Form frm = ResolveForm("Discount"); frm.ShowDialog(); The ResolveForm does the trick of building the chain of objects. Can Unity help me here? Now when I did that I did not have enough information on Unity and now that I have studied Unity I think I have been doing more or less the same thing. So I tried to replace my code with Unity. However, as soon as I started I hit a block. If I try to resolve UI forms in my Menu as Form customers = myUnityContainer.Resolve(); or Form customers = myUnityContainer.Resolve(typeof(Customers)); Then either way, I need to refer to my UI assembly from my Menu assembly since the target Type "Customers" need to be known for Unity to resolve it. So I am back to same place since I would have to refer all UI assemblies from the Menu assembly. I understand that with Unity I would have to refer fewer assemblies (only UI assemblies) but those references are needed which defeats my objectives below - Create the chain of objects dynamically without any assembly reference from Menu assembly. This is to avoid Menu source code changing every time I release a new module. My Menu also is built dynamically from a table. Be able to supply new modules just by supplying the new assemblies and inserting the new Dependency row in the table by a database patch. At this stage, I have a feeling that I have to do it the way I was doing, i.e. Activator.CreateInstance() to fulfil all my objectives. I need to verify whether the community thinks the same way as me or have a better suggestion to solve the problem. The post is really long and I sincerely thank you if you come til this point. Waiting for your valuable suggestions. Rajarshi

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• How do you send a named pipe string from umnanaged to managed code space?

  - by billmcf

  I appear to have a named pipes 101 issue. I have a very simple set up to connect a simplex named pipe transmitting from a C++ unmanaged app to a C# managed app. The pipe connects, but I cannot send a "message" through the pipe unless I close the handle which appears to flush the buffer and pass the message through. It's like the message is blocked. I have tried reversing the roles of client/server and invoking them with different Flag combinations without any luck. I can easily send messages in the other direction from C# managed to C++ unmanaged. Does anyone have any insight. Can any of you guys successfully send messages from C++ unmanaged to C# managed? I can find plenty of examples of intra amanged or unmanaged pipes but not inter managed to/from unamanged - just claims to be able to do it. In the listings, I have omitted much of the wrapper stuff for clarity. The key bits I believe that are relevant are the pipe connection/creation/read and write methods. Don't worry too much about blocking/threading here. C# Server side // This runs in its own thread and so it is OK to block private void ConnectToClient() { // This server will listen to the sending client if (m_InPipeStream == null) { m_InPipeStream = new NamedPipeServerStream("TestPipe", PipeDirection.In, 1); } // Wait for client to connect to our server m_InPipeStream.WaitForConnection(); // Verify client is running if (!m_InPipeStream.IsConnected) { return; } // Start listening for messages on the client stream if (m_InPipeStream != null && m_InPipeStream.CanRead) { ReadThread = new Thread(new ParameterizedThreadStart(Read)); ReadThread.Start(m_InPipeStream); } } // This runs in its own thread and so it is OK to block private void Read(object serverObj) { NamedPipeServerStream pipeStream = (NamedPipeServerStream)serverObj; using (StreamReader sr = new StreamReader(pipeStream)) { while (true) { string buffer = "" ; try { // Blocks here until the handle is closed by the client-side!! buffer = sr.ReadLine(); // <<<<<<<<<<<<<< Sticks here } catch { // Read error break; } // Client has disconnected? if (buffer == null || buffer.Length == 0) break; // Fire message received event if message is non-empty if (MessageReceived != null && buffer != "") { MessageReceived(buffer); } } } } C++ client side // Static - running in its own thread. DWORD CNamedPipe::ListenForServer(LPVOID arg) { // The calling app (this) is passed as the parameter CNamedPipe* app = (CNamedPipe*)arg; // Out-Pipe: connect as a client to a waiting server app->m_hOutPipeHandle = CreateFile("\\\\.\\pipe\\TestPipe", GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); // Could not create handle if (app->m_hInPipeHandle == NULL || app->m_hInPipeHandle == INVALID_HANDLE_VALUE) { return 1; } return 0; } // Sends a message to the server BOOL CNamedPipe::SendMessage(CString message) { DWORD dwSent; if (m_hOutPipeHandle == NULL || m_hOutPipeHandle == INVALID_HANDLE_VALUE) { return FALSE; } else { BOOL bOK = WriteFile(m_hOutPipeHandle, message, message.GetLength()+1, &dwSent, NULL); //FlushFileBuffers(m_hOutPipeHandle); // <<<<<<< Tried this return (!bOK || (message.GetLength()+1) != dwSent) ? FALSE : TRUE; } } // Somewhere in the Windows C++/MFC code... ... // This write is non-blocking. It just passes through having loaded the pipe. m_pNamedPipe->SendMessage("Hi de hi"); ...

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• Java code optimization leads to numerical inaccuracies and errors

  - by rano

  I'm trying to implement a version of the Fuzzy C-Means algorithm in Java and I'm trying to do some optimization by computing just once everything that can be computed just once. This is an iterative algorithm and regarding the updating of a matrix, the clusters x pixels membership matrix U, this is the update rule I want to optimize: where the x are the element of a matrix X (pixels x features) and v belongs to the matrix V (clusters x features). And m is a parameter that ranges from 1.1 to infinity. The distance used is the euclidean norm. If I had to implement this formula in a banal way I'd do: for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < V.length; j++) { double num = D[i][j]; double sumTerms = 0; for(int k = 0; k < V.length; k++) { double thisDistance = D[i][k]; sumTerms += Math.pow(num / thisDistance, (1.0 / (m - 1.0))); } U[i][j] = (float) (1f / sumTerms); } } In this way some optimization is already done, I precomputed all the possible squared distances between X and V and stored them in a matrix D but that is not enough, since I'm cycling througn the elements of V two times resulting in two nested loops. Looking at the formula the numerator of the fraction is independent of the sum so I can compute numerator and denominator independently and the denominator can be computed just once for each pixel. So I came to a solution like this: int nClusters = V.length; double exp = (1.0 / (m - 1.0)); for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < nClusters; j++) { double distance = D[i][j]; double denominator = D[i][nClusters]; double numerator = Math.pow(distance, exp); U[i][j] = (float) (1f / (numerator * denominator)); } } Where I precomputed the denominator into an additional column of the matrix D while I was computing the distances: for (int i = 0; i < X.length; i++) { for (int j = 0; j < V.length; j++) { double sum = 0; for (int k = 0; k < nDims; k++) { final double d = X[i][k] - V[j][k]; sum += d * d; } D[i][j] = sum; D[i][B.length] += Math.pow(1 / D[i][j], exp); } } By doing so I encounter numerical differences between the 'banal' computation and the second one that leads to different numerical value in U (not in the first iterates but soon enough). I guess that the problem is that exponentiate very small numbers to high values (the elements of U can range from 0.0 to 1.0 and exp , for m = 1.1, is 10) leads to ver y small values, whereas by dividing the numerator and the denominator and THEN exponentiating the result seems to be better numerically. The problem is it involves much more operations. Am I doing something wrong? Is there a possible solution to get both the code optimized and numerically stable? Any suggestion or criticism will be appreciated.

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• Linked Lists in Java - Help with assignment

  - by doron2010

  I have been trying to solve this assignment all day, please help me. I'm completely lost. Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public char charAt (int i) - returns the char in the place i in the string. Assume that the value of i is in the right range. public StringList concat (String str) - returns a string that consists of the string that it is operated on and in its end the string "str" is concatenated. public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. public int indexOf (int ch, int fromIndex) - returns the index in the string it is operated on of the first appeareance of the char "ch", as the search begins in the index "fromIndex". If the char "ch" doesn't appear in the string, returns -1. public boolean equals (String str) - returns true if the string that it is operated on is equal to the string str. Otherwise returns false. This method must be written in recursion, without using loops at all. public int compareTo (String str) - compares between the string that the method is operated on to the string "str" that is in the parameter. The method returns 0 if the strings are equal. If the string in the object is smaller lexicographic from the string "str" in the paramater, a negative number will be returned. And if the string in the object is bigger lexicographic from the string "str", a positive number will be returned. public StringList substring (int i) - returns the list of the substring that starts in the place i in the string on which it operates. Meaning, the sub-string from the place i until the end of the string. Assume the value of i is in the right range. public StringList substring (int i, int j) - returns the list of the substring that begins in the place i and ends in the place j (not included) in the string it operates on. Assume the values of i, j are in the right range. public int length() - will return the length of the string on which it operates. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations.

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• ZF: Form array field - how to display values in the view correctly

  - by Wojciech Fracz

  Let's say I have a Zend_Form form that has a few text fields, e.g: $form = new Zend_Form(); $form->addElement('text', 'name', array( 'required' => true, 'isArray' => true, 'filters' => array( /* ... */ ), 'validators' => array( /* ... */ ), )); $form->addElement('text', 'surname', array( 'required' => true, 'isArray' => true, 'filters' => array( /* ... */ ), 'validators' => array( /* ... */ ), )); After rendering it I have following HTML markup (simplified): <div id="people"> <div class="person"> <input type="text" name="name[]" /> <input type="text" name="surname[]" /> </div> </div> Now I want to have the ability to add as many people as I want. I create a "+" button that in Javascript appends next div.person to the container. Before I submit the form, I have for example 5 names and 5 surnames, posted to the server as arrays. Everything is fine unless somebody puts the value in the field that does not validate. Then the whole form validation fails and when I want to display the form again (with errors) I see the PHP Warning: htmlspecialchars() expects parameter 1 to be string, array given Which is more or less described in ticket: http://framework.zend.com/issues/browse/ZF-8112 However, I came up with a not-very-elegant solution. What I wanted to achieve: have all fields and values rendered again in the view have error messages only next to the fields that contained bad values Here is my solution (view script): <div id="people"> <?php $names = $form->name->getValue(); // will have an array here if the form were submitted $surnames= $form->surname->getValue(); // only if the form were submitted we need to validate fields' values // and display errors next to them; otherwise when user enter the page // and render the form for the first time - he would see Required validator // errors $needsValidation = is_array($names) || is_array($surnames); // print empty fields when the form is displayed the first time if(!is_array($names))$names= array(''); if(!is_array($surnames))$surnames= array(''); // display all fields! foreach($names as $index => $name): $surname = $surnames[$index]; // validate value if needed if($needsValidation){ $form->name->isValid($name); $form->surname->isValid($surname); } ?> <div class="person"> <?=$form->name->setValue($name); // display field with error if did not pass the validation ?> <?=$form->surname->setValue($surname);?> </div> <?php endforeach; ?> </div> The code work, but I want to know if there is an appropriate, more comfortable way to do this? I often hit this problem when there is a need for a more dynamic - multivalue forms and have not find better solution for a long time.

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• Problem with python class

  - by Tasbeer

  Hi I am new to Python and as a part of my assignment I have written the following class import nltk.stem.api class BanglaStemmer(nltk.stem.api.StemmerI): suffixList = ['\xef\xbb\xbf\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbe\xe0\xa6\xae\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbf\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb8\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa7\x87\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x87\xe0\xa6\x9b\n', '\xe0\xa6\xbf\xe0\xa7\x9f\xe0\xa7\x8b\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbe\xe0\xa6\xae\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbf\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb8\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa6\xbf\n', '\xe0\xa7\x87\xe0\xa6\x9b\xe0\xa7\x87\n', '\xe0\xa7\x87\xe0\xa6\x9b\n', '\xe0\xa6\xa4\xe0\xa7\x87\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbe\xe0\xa6\xae\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbf\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb8\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa6\xbf\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\xe0\xa7\x87\n', '\xe0\xa6\x9a\xe0\xa7\x8d\xe0\xa6\x9b\n', '\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbe\xe0\xa6\xae\n', '\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa7\x87\n', '\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\xe0\xa6\xbf\n', '\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb2\n', '\xe0\xa6\x9b\xe0\xa6\xbf\xe0\xa6\xb8\n', '\xe0\xa6\x9b\xe0\xa6\xbf\n', '\xe0\xa6\x9b\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\x9b\n', '\xe0\xa6\xa4\xe0\xa6\xbf\xe0\xa6\xb8\n', '\xe0\xa6\xa4\xe0\xa6\xbe\xe0\xa6\xae\n', '\xe0\xa6\xb2\xe0\xa6\xbe\xe0\xa6\xae\n', '\xe0\xa6\xb2\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\xa4\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\xac\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa7\x87\xe0\xa6\xa8\n', '\xe0\xa6\xbf\xe0\xa6\xb8\n', '\xe0\xa7\x81\xe0\xa6\xa8\n', '\xe0\xa7\x81\xe0\xa6\x95\n', '\xe0\xa6\xb2\xe0\xa7\x87\n', '\xe0\xa6\xac\xe0\xa7\x87\n', '\xe0\xa6\xb2\xe0\xa6\xbf\n', '\xe0\xa6\xac\xe0\xa6\xbf\n', '\xe0\xa6\xa4\xe0\xa6\xbf\n', '\xe0\xa6\xb2\n', '\xe0\xa6\xa4\n', '\xe0\xa7\x8b\n', '\xe0\xa6\xbf\n', '\xe0\xa7\x87\n', '\xe0\xa7\x8d\n', '\xe0\xa6\x87\n', '\xe0\xa6\xac\n', '\xe0\xa6\xb8\n', '\xe0\xa6\xa8\n', '\xe0\xa6\x95\n', '\xe0\xa6\x93\n', '\xe0\xa7\x9f\n'] def stem(self,token): for suffix in suffixList: if token.endswith(suffix): return token[:-len(suffix)] return token The problem is that when I try to compile run it by creating an instance and calling the stem() function with a parameter , it says that the suffixList is not defined. Couldn't figure out what's the problem. Is there a different way in which the class variables have to be declared ? please help

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• Type for use in template object to compare double values

  - by DaClown

  I got this n-dimensional point object: template <class T, unsigned int dimension> class Obj { protected: T coords[dimension]; static const unsigned int size = dimension; public: Obj() { }; Obj(T def) { for (unsigned int i = 0; i < size; ++i) coords[i]=def; }; Obj(const Obj& o) { for (unsigned int i = 0; i < size; ++i) coords[i] = o.coords[i]; } const Obj& operator= (const Obj& rhs) { if (this != &rhs) for (unsigned int i = 0; i < size; ++i) coords[i] = rhs.coords[i]; return *this; } virtual ~Obj() { }; T get (unsigned int id) { if (id >= size) throw std::out_of_range("out of range"); return coords[id]; } void set (unsigned int id, T t) { if (id >= size) throw std::out_of_range("out of range"); coords[id] = t; } }; and a 3D point class which uses Obj as base class: template <class U> class Point3DBase : public Obj<U,3> { typedef U type; public: U &x, &y, &z; public: Point3DBase() : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { }; Point3DBase(U def) : Obj<U,3>(def), x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { }; Point3DBase(U x_, U y_, U z_) : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { x = x_; y = y_; z= z_; }; Point3DBase(const Point3DBase& other) : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { x = other.x; y = other.y; z = other.z; } // several operators ... }; The operators, basically the ones for comparison, use the simple compare-the-member-object approach like: virtual friend bool operator== (const Point3DBase<U> &lhs, const Point3DBase<U> rhs) { return (lhs.x == rhs.x && lhs.y == rhs.y && lhs.z == rhs.z); } Then it occured to me that for the comparion of double values the simply equality approach is not very useful since double values should be compared with an error margin. What would be the best approach to introduce an error margin into the point? I thought about an epsDouble type as template parameter but I can't figure out how to achieve this.

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• Fill container with template parameters

  - by phlipsy

  I want to fill the template parameters passed to a variadic template into an array with fixed length. For that purpose I wrote the following helper function templates template<typename ForwardIterator, typename T> void fill(ForwardIterator i) { } template<typename ForwardIterator, typename T, T head, T... tail> void fill(ForwardIterator i) { *i = head; fill<ForwardIterator, T, tail...>(++i); } the following class template template<typename T, T... args> struct params_to_array; template<typename T, T last> struct params_to_array<T, last> { static const std::size_t SIZE = 1; typedef std::array<T, SIZE> array_type; static const array_type params; private: void init_params() { array_type result; fill<typename array_type::iterator, T, head, tail...>(result.begin()); return result; } }; template<typename T, T head, T... tail> struct params_to_array<T, head, tail...> { static const std::size_t SIZE = params_to_array<T, tail...>::SIZE + 1; typedef std::array<T, SIZE> array_type; static const array_type params; private: void init_params() { array_type result; fill<typename array_type::iterator, T, last>(result.begin()); return result; } }; and initialized the static constants via template<typename T, T last> const typename param_to_array<T, last>::array_type param_to_array<T, last>::params = param_to_array<T, last>::init_params(); and template<typename T, T head, T... tail> const typename param_to_array<T, head, tail...>::array_type param_to_array<T, head, tail...>::params = param_to_array<T, head, tail...>::init_params(); Now the array param_to_array<int, 1, 3, 4>::params is a std::array<int, 3> and contains the values 1, 3 and 4. I think there must be a simpler way to achieve this behavior. Any suggestions? Edit: As Noah Roberts suggested in his answer I modified my program like the following: I wrote a new struct counting the elements in a parameter list: template<typename T, T... args> struct count; template<typename T, T head, T... tail> struct count<T, head, tail...> { static const std::size_t value = count<T, tail...>::value + 1; }; template<typename T, T last> stuct count<T, last> { static const std::size_t value = 1; }; and wrote the following function template<typename T, T... args> std::array<T, count<T, args...>::value> params_to_array() { std::array<T, count<T, args...>::value> result; fill<typename std::array<T, count<T, args...>::value>::iterator, T, args...>(result.begin()); return result; } Now I get with params_to_array<int, 10, 20, 30>() a std::array<int, 3> with the content 10, 20 and 30. Any further suggestions?

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• Need a hand understanding this Java code please :-)

  - by Brian

  Hi all, Just wondering if anyone would be able to take a look at this code for implementing the quicksort algorithm and answer me a few questions, please :-) public class Run { /*************************************************************************** * Quicksort code from Sedgewick 7.1, 7.2. **************************************************************************/ public static void quicksort(double[] a) { //shuffle(a); // to guard against worst-case quicksort(a, 0, a.length - 1, 0); } static void quicksort(final double[] a, final int left, final int right, final int tdepth) { if (right <= left) return; final int i = partition(a, left, right); if ((tdepth < 4) && ((i - left) > 1000)) { final Thread t = new Thread() { public void run() { quicksort(a, left, i - 1, tdepth + 1); } }; t.start(); quicksort(a, i + 1, right, tdepth + 1); try { t.join(); } catch (InterruptedException e) { throw new RuntimeException("Cancelled", e); } } else { quicksort(a, left, i - 1, tdepth); quicksort(a, i + 1, right, tdepth); } } // partition a[left] to a[right], assumes left < right private static int partition(double[] a, int left, int right) { int i = left - 1; int j = right; while (true) { while (less(a[++i], a[right])) // find item on left to swap ; // a[right] acts as sentinel while (less(a[right], a[--j])) // find item on right to swap if (j == left) break; // don't go out-of-bounds if (i >= j) break; // check if pointers cross exch(a, i, j); // swap two elements into place } exch(a, i, right); // swap with partition element return i; } // is x < y ? private static boolean less(double x, double y) { return (x < y); } // exchange a[i] and a[j] private static void exch(double[] a, int i, int j) { double swap = a[i]; a[i] = a[j]; a[j] = swap; } // shuffle the array a[] private static void shuffle(double[] a) { int N = a.length; for (int i = 0; i < N; i++) { int r = i + (int) (Math.random() * (N - i)); // between i and N-1 exch(a, i, r); } } // test client public static void main(String[] args) { int N = 5000000; // Integer.parseInt(args[0]); // generate N random real numbers between 0 and 1 long start = System.currentTimeMillis(); double[] a = new double[N]; for (int i = 0; i < N; i++) a[i] = Math.random(); long stop = System.currentTimeMillis(); double elapsed = (stop - start) / 1000.0; System.out.println("Generating input: " + elapsed + " seconds"); // sort them start = System.currentTimeMillis(); quicksort(a); stop = System.currentTimeMillis(); elapsed = (stop - start) / 1000.0; System.out.println("Quicksort: " + elapsed + " seconds"); } } My questions are: What is the purpose of the variable tdepth? Is this considered a "proper" implementation of a parallel quicksort? I ask becuase it doesn't use implements Runnable or extends Thread... If it doesn't already, is it possible to modify this code to use multiple threads? By passing in the number of threads you want to use as a parameter, for example...? Many thanks, Brian

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• Adjust parameters of serial port reading

  - by clinisbut

  Hello. I'm facing a particular issue that regards serial communication under win32. I'm communicating with a device can only accept frames when it is not already communicating. So I must find a valid frame and then inmediatelly send my request. I developed a class named Serial that handles basic operations on serial port (open, close, read, write) and then a Thread calls inside a loop read and write functions. Thread loop //Device is an object of class Serial while( device->isOpen() && !terminate ) { unsigned int readed = 0; unsigned long error = ERROR_SUCCESS; unsigned char* data = device->read( &readed, &error ); if( error==ERROR_SUCCESS ) { //If data received, deliver to upper level if( readed>0 ) { QByteArray output( (const char*)data, (signed int)readed ); emit dataArrived( output, readed ); } } else { //unrelated stuff } //Here I manage the writting issue //Only when nothing is received, and Upper layer wants to send a frame //(Upper layer only will mark as something to send when it detects a valid frame) if( readed==0 ) { out_lock.lock(); //If something to send... if( something_to_send > 0 ) { if( device->write( output_buffer, output_size, &error ) ) { //things... } } } } The Thread basically keeps reading, and when nothing is received, sees if somebody has signaled to send a frame (this means that a valid frame is just received). When this happens, it writes the frame through serial port. Here comes my problem. Inside the Serial::read() function: I use the overlapped way of reading: ::ClearCommError( handle, &dwErrors, &stat); if( stat.cbInQue ) { //If there's something to read, read it, please note the bytes to read parameter, here 1. bool ok = ::ReadFile( handle, buffer_in, 1, &bytes_read, &ov_reader ); if( !ok ) { DWORD _error = ::GetLastError(); if( _error == ERROR_IO_PENDING ) { DWORD result = ::WaitForMultipleObjects( 2, waiters, FALSE,INFINITE ); switch( result ) { //Eventshutdown case WAIT_OBJECT_0: /*code omitted*/break; case WAIT_OBJECT_0+1: ok = ::GetOverlappedResult( handle, &ov_reader, &bytes_read, true ); //check ok value omitted break; } } } } if( bytes_read>0 ) { *size = bytes_read; } Here starts my problem. When device sends me small frames (around 30 bytes) everything works fine, but when larger frames are sent, the code is not able to find any free time between frames causing the thread to never be able send any frame because readed is never 0. If I increase the number of bytes to read inside the read() function, lose the ability to detect when the device "listens": bool ok = ::ReadFile(handle, buffer_in, 50, &bytes_read, &ov_reader ); This happens because my app can receive the end of a frame together with the start of the next one. This behaviour is very common. In the other hand, if I change the INFINITE argument by a valid timeout in the WaitForMultipleObjects function, I lose data. So my question basically is... what I'm doing wrong? Why when reading 1 byte each time I don't find any free time to send my own frames? Thank you

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• C++ copy-construct construct-and-assign question

  - by Andy

  Blockquote Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is accomplished through a direct invocation of Y::Y(int). The initializations of b and c are more complex. In fact, they're too complex. These are both copy initializations. In the case of the initialization of b, we're requesting the creation of an anonymous temporary of type Y, initialized with the value 1066. We then use this anonymous temporary as a parameter to the copy constructor for class Y to initialize b. Finally, we call the destructor for the anonymous temporary. To test this, I did a simple class with a data member (program attached at the end) and the results were surprising. It seems that for the case of b, the object was constructed by the copy constructor rather than as suggested in the book. Does anybody know if the language standard has changed or is this simply an optimisation feature of the compiler? I was using Visual Studio 2008. Code sample: #include <iostream> class Widget { std::string name; public: // Constructor Widget(std::string n) { name=n; std::cout << "Constructing Widget " << this->name << std::endl; } // Copy constructor Widget (const Widget& rhs) { std::cout << "Copy constructing Widget from " << rhs.name << std::endl; } // Assignment operator Widget& operator=(const Widget& rhs) { std::cout << "Assigning Widget from " << rhs.name << " to " << this->name << std::endl; return *this; } }; int main(void) { // construct Widget a("a"); // copy construct Widget b(a); // construct and assign Widget c("c"); c = a; // copy construct! Widget d = a; // construct! Widget e = "e"; // construct and assign Widget f = Widget("f"); return 0; } Output: Constructing Widget a Copy constructing Widget from a Constructing Widget c Assigning Widget from a to c Copy constructing Widget from a Constructing Widget e Constructing Widget f Copy constructing Widget from f I was most surprised by the results of constructing d and e.

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• hosting simple python scripts in a container to handle concurrency, configuration, caching, etc.

  - by Justin Grant

  My first real-world Python project is to write a simple framework (or re-use/adapt an existing one) which can wrap small python scripts (which are used to gather custom data for a monitoring tool) with a "container" to handle boilerplate tasks like: fetching a script's configuration from a file (and keeping that info up to date if the file changes and handle decryption of sensitive config data) running multiple instances of the same script in different threads instead of spinning up a new process for each one expose an API for caching expensive data and storing persistent state from one script invocation to the next Today, script authors must handle the issues above, which usually means that most script authors don't handle them correctly, causing bugs and performance problems. In addition to avoiding bugs, we want a solution which lowers the bar to create and maintain scripts, especially given that many script authors may not be trained programmers. Below are examples of the API I've been thinking of, and which I'm looking to get your feedback about. A scripter would need to build a single method which takes (as input) the configuration that the script needs to do its job, and either returns a python object or calls a method to stream back data in chunks. Optionally, a scripter could supply methods to handle startup and/or shutdown tasks. HTTP-fetching script example (in pseudocode, omitting the actual data-fetching details to focus on the container's API): def run (config, context, cache) : results = http_library_call (config.url, config.http_method, config.username, config.password, ...) return { html : results.html, status_code : results.status, headers : results.response_headers } def init(config, context, cache) : config.max_threads = 20 # up to 20 URLs at one time (per process) config.max_processes = 3 # launch up to 3 concurrent processes config.keepalive = 1200 # keep process alive for 10 mins without another call config.process_recycle.requests = 1000 # restart the process every 1000 requests (to avoid leaks) config.kill_timeout = 600 # kill the process if any call lasts longer than 10 minutes Database-data fetching script example might look like this (in pseudocode): def run (config, context, cache) : expensive = context.cache["something_expensive"] for record in db_library_call (expensive, context.checkpoint, config.connection_string) : context.log (record, "logDate") # log all properties, optionally specify name of timestamp property last_date = record["logDate"] context.checkpoint = last_date # persistent checkpoint, used next time through def init(config, context, cache) : cache["something_expensive"] = get_expensive_thing() def shutdown(config, context, cache) : expensive = cache["something_expensive"] expensive.release_me() Is this API appropriately "pythonic", or are there things I should do to make this more natural to the Python scripter? (I'm more familiar with building C++/C#/Java APIs so I suspect I'm missing useful Python idioms.) Specific questions: is it natural to pass a "config" object into a method and ask the callee to set various configuration options? Or is there another preferred way to do this? when a callee needs to stream data back to its caller, is a method like context.log() (see above) appropriate, or should I be using yield instead? (yeild seems natural, but I worry it'd be over the head of most scripters) My approach requires scripts to define functions with predefined names (e.g. "run", "init", "shutdown"). Is this a good way to do it? If not, what other mechanism would be more natural? I'm passing the same config, context, cache parameters into every method. Would it be better to use a single "context" parameter instead? Would it be better to use global variables instead? Finally, are there existing libraries you'd recommend to make this kind of simple "script-running container" easier to write?

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• sherlock actionbar menu

  - by user1647443

  I am trying to setup a menu programatically and my method gets com.actionbarsherlock.view.Menu menu as a parameter. As I want to change the styling of the menu item I am trying to setup a SpannableString spannable and pass it to add. menu.add(0, MENU_ABOUT, 0, spannable); This is causing a crash only in ICS when I cick that menu item. Any ideas if I am missing something. Thanks Here is the code I am trying and it crashes when I run the app and select "About Application". FYI, I am using SpannableString because I want to add some styling and color to the menu item. The crash does NOT happen if I use a regular string, but then I cant do styling public boolean onCreateOptionsMenu(com.actionbarsherlock.view.Menu menu) { SpannableString spannable = new SpannableString("About Application"); menu.add(0, MENU_ABOUT, 0, spannable); return true; } Here is the stack trace: 09-05 02:25:32.849: E/AndroidRuntime(684): FATAL EXCEPTION: main 09-05 02:25:32.849: E/AndroidRuntime(684): java.lang.IllegalArgumentException: Invalid payload item type 09-05 02:25:32.849: E/AndroidRuntime(684): at android.util.EventLog.writeEvent(Native Method) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.app.Activity.onMenuItemSelected(Activity.java:2501) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:351) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:950) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.view.menu.ListMenuPresenter.onItemClick(ListMenuPresenter.java:163) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.widget.AdapterView.performItemClick(AdapterView.java:292) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.widget.AbsListView.performItemClick(AbsListView.java:1058) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2514) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.widget.AbsListView.onTouchEvent(AbsListView.java:3180) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.View.dispatchTouchEvent(View.java:5541) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1951) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1712) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1860) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.View.dispatchPointerEvent(View.java:5721) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:2890) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2466) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewRootImpl.processInputEvents(ViewRootImpl.java:845) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2475) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.os.Handler.dispatchMessage(Handler.java:99) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.os.Looper.loop(Looper.java:137) 09-05 02:25:32.849: E/AndroidRuntime(684): at android.app.ActivityThread.main(ActivityThread.java:4424) 09-05 02:25:32.849: E/AndroidRuntime(684): at java.lang.reflect.Method.invokeNative(Native Method) 09-05 02:25:32.849: E/AndroidRuntime(684): at java.lang.reflect.Method.invoke(Method.java:511) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 09-05 02:25:32.849: E/AndroidRuntime(684): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 09-05 02:25:32.849: E/AndroidRuntime(684): at dalvik.system.NativeStart.main(Native Method) Thanks

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• NHibernate: How is identity Id updated when saving a transient instance?

  - by bretddog

  If I use session-per-transaction and call: session.SaveOrUpdate(entity) corrected: session.SaveOrUpdateCopy(entity) ..and entity is a transient instance with identity-Id=0. Shall the above line automatically update the Id of the entity, and make the instance persistent? Or should it do so on transaction.Commit? Or do I have to somehow code that explicitly? Obviously the Id of the database row (new, since transient) is autogenerated and saved as some number, but I'm talking about the actual parameter instance here. Which is the business logic instance. EDIT Mappings: public class StoreMap : ClassMap<Store> { public StoreMap() { Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.Name); HasMany(x => x.Staff) // 1:m .Cascade.All(); HasManyToMany(x => x.Products) // m:m .Cascade.All() .Table("StoreProduct"); } } public class EmployeeMap : ClassMap<Employee> { public EmployeeMap() { Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.FirstName); Map(x => x.LastName); References(x => x.Store); // m:1 } } public class ProductMap : ClassMap<Product> { public ProductMap() { Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.Name).Length(20); Map(x => x.Price).CustomSqlType("decimal").Precision(9).Scale(2); HasManyToMany(x => x.StoresStockedIn) .Cascade.All() .Inverse() .Table("StoreProduct"); } } EDIT2 Class definitions: public class Store { public int Id { get; private set; } public string Name { get; set; } public IList<Product> Products { get; set; } public IList<Employee> Staff { get; set; } public Store() { Products = new List<Product>(); Staff = new List<Employee>(); } // AddProduct & AddEmployee is required. "NH needs you to set both sides before // it will save correctly" public void AddProduct(Product product) { product.StoresStockedIn.Add(this); Products.Add(product); } public void AddEmployee(Employee employee) { employee.Store = this; Staff.Add(employee); } } public class Employee { public int Id { get; private set; } public string FirstName { get; set; } public string LastName { get; set; } public Store Store { get; set; } } public class Product { public int Id { get; private set; } public string Name { get; set; } public decimal Price { get; set; } public IList<Store> StoresStockedIn { get; private set; } }

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• Getting the constructor of an Interface Type through reflection?

  - by Will Marcouiller

  I have written a generic type: IDirectorySource<T> where T : IDirectoryEntry, which I'm using to manage Active Directory entries through my interfaces objects: IGroup, IOrganizationalUnit, IUser. So that I can write the following: IDirectorySource<IGroup> groups = new DirectorySource<IGroup>(); // Where IGroup implements `IDirectoryEntry`, of course.` foreach (IGroup g in groups.ToList()) { listView1.Items.Add(g.Name).SubItems.Add(g.Description); } From the IDirectorySource<T>.ToList() methods, I use reflection to find out the appropriate constructor for the type parameter T. However, since T is given an interface type, it cannot find any constructor at all! Of course, I have an internal class Group : IGroup which implements the IGroup interface. No matter how hard I have tried, I can't figure out how to get the constructor out of my interface through my implementing class. [DirectorySchemaAttribute("group")] public interface IGroup { } internal class Group : IGroup { internal Group(DirectoryEntry entry) { NativeEntry = entry; Domain = NativeEntry.Path; } // Implementing IGroup interface... } Within the ToList() method of my IDirectorySource<T> interface implementation, I look for the constructor of T as follows: internal class DirectorySource<T> : IDirectorySource<T> { // Implementing properties... // Methods implementations... public IList<T> ToList() { Type t = typeof(T) // Let's assume we're always working with the IGroup interface as T here to keep it simple. // So, my `DirectorySchema` property is already set to "group". // My `DirectorySearcher` is already instantiated here, as I do it within the DirectorySource<T> constructor. Searcher.Filter = string.Format("(&(objectClass={0}))", DirectorySchema) ConstructorInfo ctor = null; ParameterInfo[] params = null; // This is where I get stuck for now... Please see the helper method. GetConstructor(out ctor, out params, new Type() { DirectoryEntry }); SearchResultCollection results = null; try { results = Searcher.FindAll(); } catch (DirectoryServicesCOMException ex) { // Handling exception here... } foreach (SearchResult entry in results) entities.Add(ctor.Invoke(new object() { entry.GetDirectoryEntry() })); return entities; } } private void GetConstructor(out ConstructorInfo constructor, out ParameterInfo[] parameters, Type paramsTypes) { Type t = typeof(T); ConstructorInfo[] ctors = t.GetConstructors(BindingFlags.CreateInstance | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.InvokeMethod); bool found = true; foreach (ContructorInfo c in ctors) { parameters = c.GetParameters(); if (parameters.GetLength(0) == paramsTypes.GetLength(0)) { for (int index = 0; index < parameters.GetLength(0); ++index) { if (!(parameters[index].GetType() is paramsTypes[index].GetType())) found = false; } if (found) { constructor = c; return; } } } // Processing constructor not found message here... } My problem is that T will always be an interface, so it never finds a constructor. Might somebody guide me to the right path to follow in this situation?

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• Problem detaching entire object graph in GAE-J with JDO

  - by tempy

  I am trying to load the full object graph for User, which contains a collection of decks, which then contains a collection of cards, as such: User: @PersistenceCapable(detachable = "true") @Inheritance(strategy = InheritanceStrategy.SUBCLASS_TABLE) @FetchGroup(name = "decks", members = { @Persistent(name = "_Decks") }) public abstract class User { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) protected Key _ID; @Persistent protected String _UniqueIdentifier; @Persistent(mappedBy = "_Owner") @Element(dependent = "true") protected Set<Deck> _Decks; protected User() { } } Each Deck has a collection of Cards, as such: @PersistenceCapable(detachable = "true") @FetchGroup(name = "cards", members = { @Persistent(name = "_Cards") }) public class Deck { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key _ID; @Persistent String _Name; @Persistent(mappedBy = "_Parent") @Element(dependent = "true") private Set<Card> _Cards = new HashSet<Card>(); @Persistent private Set<String> _Tags = new HashSet<String>(); @Persistent private User _Owner; } And finally, each card: @PersistenceCapable public class Card { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key _ID; @Persistent private Text _Question; @Persistent private Text _Answer; @Persistent private Deck _Parent; } I am trying to retrieve and then detach the entire object graph. I can see in the debugger that it loads fine, but then when I get to detaching, I can't make anything beyond the User object load. (No Decks, no Cards). At first I tried without a transaction to simply "touch" all the fields on the attached object before detaching, but that didn't help. Then I tried adding everything to the default fetch group, but that just generated warnings about GAE not supporting joins. I tried setting the fetch plan's max fetch depth to -1, but that didn't do it. Finally, I tried using FetchGroups as you can see above, and then retrieving with the following code: PersistenceManager pm = _pmf.getPersistenceManager(); pm.setDetachAllOnCommit(true); pm.getFetchPlan().setGroup("decks"); pm.getFetchPlan().setGroup("cards"); Transaction tx = pm.currentTransaction(); Query query = null; try { tx.begin(); query = pm.newQuery(GoogleAccountsUser.class); //Subclass of User query.setFilter("_UniqueIdentifier == TheUser"); query.declareParameters("String TheUser"); List<User> results = (List<User>)query.execute(ID); //ID = Supplied parameter //TODO: Test for more than one result and throw if(results.size() == 0) { tx.commit(); return null; } else { User usr = (User)results.get(0); //usr = pm.detachCopy(usr); tx.commit(); return usr; } } finally { query.closeAll(); if (tx.isActive()) { tx.rollback(); } pm.close(); } This also doesn't work, and I'm running out of ideas...

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