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  • Implementing the tree with reference to the root for each leaf

    - by AntonAL
    Hi, i implementing a products catalog, that looks, like this: group 1 subgroup 1 subgroup 2 item 1 item 2 ... item n ... subgroup n group 2 subgroup 1 ... subgroup n group 3 ... group n The Models: class CatalogGroup < ActiveRecord::Base has_many: catalog_items has_many :catalog_items_all, :class_name => "CatalogItem", :foreign_key => "catalog_root_group_id" end class CatalogItem < ActiveRecord::Base belongs_to :catalog_group belongs_to :catalog_root_group, :class_name => "CatalogGroup" end Migrations: class CreateCatalogItems < ActiveRecord::Migration def self.up create_table :catalog_items do |t| t.integer :catalog_group_id t.integer :catalog_root_group_id t.string :code t.timestamps end end For convenience, i referenced each CatalogItem to it's top-most CatalogGroup and named this association "catalog_root_group". This will give us the simple implementation of search request, like "show me all items in group 1". We will have a deal only with CatalogModel.catalog_root_group The problem is - this association does't work. I always get "catalog_root_group" equals to nil Also, i have tried to overcome the using of reference to root group ("catalog_root_group"), but i cannot construct appropriate search request in ruby ... Do you know, how to do it ?

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  • IUsable: controlling resources in a better way than IDisposable

    - by Ilya Ryzhenkov
    I wish we have "Usable" pattern in C#, when code block of using construct would be passed to a function as delegate: class Usable : IUsable { public void Use(Action action) // implements IUsable { // acquire resources action(); // release resources } } and in user code: using (new Usable()) { // this code block is converted to delegate and passed to Use method above } Pros: Controlled execution, exceptions The fact of using "Usable" is visible in call stack Cons: Cost of delegate Do you think it is feasible and useful, and if it doesn't have any problems from the language point of view? Are there any pitfalls you can see? EDIT: David Schmitt proposed the following using(new Usable(delegate() { // actions here }) {} It can work in the sample scenario like that, but usually you have resource already allocated and want it to look like this: using (Repository.GlobalResource) { // actions here } Where GlobalResource (yes, I know global resources are bad) implements IUsable. You can rewrite is as short as Repository.GlobalResource.Use(() => { // actions here }); But it looks a little bit weird (and more weird if you implement interface explicitly), and this is so often case in various flavours, that I thought it deserve to be new syntactic sugar in a language.

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  • Using Grapher on GIN application with GinModuleAdapter

    - by Epaga
    I've been trying to use Grapher on my GIN project. But trying to create an Injector to give the InjectorGrapher has not been working. Right in the first line of my code: Injector injector = Guice.createInjector( new GinModuleAdapter( new MyGinModule() ) ); it crashes with Exception in thread "main" java.lang.AssertionError: should never be actually called at com.google.gwt.inject.rebind.adapter.GwtDotCreateProvider.get(GwtDotCreateProvider.java:43) at com.google.inject.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:48) at com.google.inject.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:45) at com.google.inject.InjectorImpl.callInContext(InjectorImpl.java:811) at com.google.inject.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:42) at com.google.inject.Scopes$1$1.get(Scopes.java:54) at com.google.inject.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:48) at com.google.inject.SingleParameterInjector.inject(SingleParameterInjector.java:42) at com.google.inject.SingleParameterInjector.getAll(SingleParameterInjector.java:66) at com.google.inject.ConstructorInjector.construct(ConstructorInjector.java:84) at com.google.inject.ConstructorBindingImpl$Factory.get(ConstructorBindingImpl.java:111) at com.google.inject.BoundProviderFactory.get(BoundProviderFactory.java:56) at com.google.inject.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:45) at com.google.inject.InjectorImpl.callInContext(InjectorImpl.java:811) at com.google.inject.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:42) at com.google.inject.Scopes$1$1.get(Scopes.java:54) at com.google.inject.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:48) at com.google.inject.InjectorBuilder$1.call(InjectorBuilder.java:200) at com.google.inject.InjectorBuilder$1.call(InjectorBuilder.java:194) at com.google.inject.InjectorImpl.callInContext(InjectorImpl.java:804) at com.google.inject.InjectorBuilder.loadEagerSingletons(InjectorBuilder.java:194) at com.google.inject.InjectorBuilder.injectDynamically(InjectorBuilder.java:176) at com.google.inject.InjectorBuilder.build(InjectorBuilder.java:113) at com.google.inject.Guice.createInjector(Guice.java:92) at com.google.inject.Guice.createInjector(Guice.java:69) at com.google.inject.Guice.createInjector(Guice.java:59) at com.me.myself.Grapher.main(Grapher.java:20) What gives?

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  • Embedded SQL in OO languages like Java

    - by Steve De Caux
    One of the things that annoys me working with SQL in OO languages is having to define SQL statements in strings. When I used to work on IBM mainframes, the languages used an SQL preprocessor to parse SQL statements out of the native code, so the statements could be written in cleartext SQL without the obfuscation of strings, for instance in Cobol there is a EXEC SQL .... END-EXEC syntax construct that allows pure SQL statements to be embedded in the Cobol code. <pure cobol code, including assignment of value to local variable HOSTVARIABLE> EXEC SQL SELECT COL_A, COL_B, COL_C INTO :COLA, :COLB, :COLC FROM TAB_A WHERE COL_D = :HOSTVARIABLE END_EXEC <more cobol code, variables COLA, COLB, COLC have been set> ...this makes the SQL statement really easy to read & check for errors. Between the EXEC SQL .... END-EXEC tokens there are no constraints on indentation, linebreaking etc., so you can format the SQL statement according to taste. Note that this example is for a single-row select, when a multiple-row resultset is expected, the coding is different (but still v. easy to read). So, taking Java as an example What made the "old COBOL" approach undesirable ? Not only SQL, but system calls could be made much more readable with that approach. Let's call it the embedded foreign language preprocessor approach. Would an embedded foreign language preprocessor for SQL be useful to implement ? Would you see a benefit in being able to write native SQL statements inside java code ? Edit I'm really asking if you think SQL in OO languages is a throwback, and if not then what could be done to make it better.

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  • Can I build this XPath query dynamically in XSLT?

    - by Martin Doms
    I have a document that looks something like <root> <element> <subelement1 /> <subelement2 /> </element> <element> <subelement2 /> <subelement1 /> </element> </root> In my XSLT sheet in the context of /element[2]/[someNode] I want to get a number that represents the distance of /element[1]/[someNode] (ie, the number of preceding siblings of /element1/[someNode]). For example, in the context of /element[2]/subelement1 I'd like to have some way to get the number 2, the distance from /element[1] to /element[1]/subelement2. I only ever need the distance of the given node name from the first instance of . Intuitively I thought I could construct this like <xsl:variable name="nodename" select="name()" /> <xsl:value-of select="/element[1]/$nodename/preceding-sibling::*" /> but unfortunately this sheet doesn't compile. Is what I'm trying to achieve possible in XSLT?

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  • ASP Calendar Date Pick

    - by Steven
    I am attempting to construct my own date picker using code from several sources. Specifically, I am now populating the textbox with a calendar click. Two questions: Why does the first click refresh the page without doing anything? How can I have the textbox update without refreshing the entire page? myDate.ascx <%@ Control Language="vb" AutoEventWireup="false" CodeBehind="myDate.ascx.vb" Inherits="Website.myDate" %> <script language="javascript" type="text/javascript"> function toggleCalendar(myID) { var obj = document.getElementById(myID) obj.style.display = (obj.style.display == "none") ? "" : "none"; } </script> <asp:TextBox ID="dateText" runat="server" > </asp:TextBox> <input type="button" name="dateBtn" value="x" onclick="toggleCalendar('<%=dateCal.clientID%>');" /> <asp:Calendar ID="dateCal" runat="server" ></asp:Calendar> myDate.ascx.vb Partial Public Class myDate Inherits System.Web.UI.UserControl Protected Sub dateCal_SelectionChanged _ (ByVal sender As Object, ByVal e As EventArgs) _ Handles dateCal.SelectionChanged dateText.Text = dateCal.SelectedDate 'update text box' dateCal.Style("display") = "none" 'hide calendar' End Sub End Class

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  • Automation Error when exporting Excel data to SQL Server

    - by brohjoe
    I'm getting an Automation error upon running VBA code in Excel 2007. I'm attempting to connect to a remote SQL Server DB and load data to from Excel to SQL Server. The error I get is, "Run-time error '-2147217843(80040e4d)': Automation error". I checked out the MSDN site and it suggested that this may be due to a bug associated with the sqloledb provider and one way to mitigate this is to use ODBC. Well I changed the connection string to reflect ODBC provider and associated parameters and I'm still getting the same error. Here is the code with ODBC as the provider: Dim cnt As ADODB.Connection Dim rst As ADODB.Recordset Dim stSQL As String Dim wbBook As Workbook Dim wsSheet As Worksheet Dim rnStart As Range Public Sub loadData() 'This was set up using Microsoft ActiveX Data Components version 6.0. 'Create ADODB connection object, open connection and construct the connection string object. Set cnt = New ADODB.Connection cnt.ConnectionString = "Driver={SQL Server}; Server=onlineSQLServer2010.foo.com; Database=fooDB;Uid=logonalready;Pwd='helpmeOB1';" cnt.Open On Error GoTo ErrorHandler 'Open Excel and run query to export data to SQL Server. strSQL = "SELECT * INTO SalesOrders FROM OPENDATASOURCE('Microsoft.ACE.OLEDB.12.0'," & _ "'Data Source=C:\Database.xlsx; Extended Properties=Excel 12.0')...[SalesOrders$]" cnt.Execute (strSQL) 'Error handling. ErrorExit: 'Reclaim memory from the connection objects Set rst = Nothing Set cnt = Nothing Exit Sub ErrorHandler: MsgBox Err.Description, vbCritical Resume ErrorExit 'clean up and reclaim memory resources. If CBool(cnt.State And adStateOpen) Then Set rst = Nothing Set cnt = Nothing cnt.Close End If End Sub

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  • Producer/consumer system using database (MySql), is this feasible?

    - by johnrl
    Hi all. I need to use something to coordinate my system with several consumers/producers each running on different machines with different operating systems. I have been researching on using MySql to do this, but it seems ridiculously difficult. My requirements are simple: I want to be able to add or remove consumers/producers at any time and thus they should not depend on each other at all. Naturally a database would separate the two nicely. I have been looking at Q4M message queuing plugin for MySql but it seems complicated to use: I have to recompile it every time I upgrade MySql (can this really be true?) because when I try to install it on Ubuntu 9.10 with MySql 5.1.37 it says "Can't open shared library 'libqueue_engine.so' (errno: 0 API version for STORAGE ENGINE plugin is too different)". There is no precompiled version for MySql 5.1.37 apparently. Also what if I want to run MySql on my windows machine, then I can't rely on this plugin as it only seems to run on Linux and OSX?? I really need some input on how to construct my system best possible.

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  • How will Arel affect rails' includes() 's capabilities.

    - by Tim Snowhite
    I've looked over the Arel sources, and some of the activerecord sources for Rails 3.0, but I can't seem to glean a good answer for myself as to whether Arel will be changing our ability to use includes(), when constructing queries, for the better. There are instances when one might want to modify the conditions on an activerecord :include query in 2.3.5 and before, for the association records which would be returned. But as far as I know, this is not programmatically tenable for all :include queries: (I know some AR-find-includes make t#{n}.c#{m} renames for all the attributes, and one could conceivably add conditions to these queries to limit the joined sets' results; but others do n_joins + 1 number of queries over the id sets iteratively, and I'm not sure how one might hack AR to edit these iterated queries.) Will Arel allow us to construct ActiveRecord queries which specify the resulting associated model objects when using includes()? Ex: User :has_many posts( has_many :comments) User.all(:include => :posts) #say I wanted the post objects to have their #comment counts loaded without adding a comment_count column to `posts`. #At the post level, one could do so by: posts_with_counts = Post.all(:select => 'posts.*, count(comments.id) as comment_count', :joins => 'left outer join comments on comments.post_id = posts.id', :group_by => 'posts.id') #i believe #But it seems impossible to do so while linking these post objects to each #user as well, without running User.all() and then zippering the objects into #some other collection (ugly) #OR running posts.group_by(&:user) (even uglier, with the n user queries)

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  • Converting a Linq expression tree that relies on SqlMethods.Like() for use with the Entity Framework

    - by JohnnyO
    I recently switched from using Linq to Sql to the Entity Framework. One of the things that I've been really struggling with is getting a general purpose IQueryable extension method that was built for Linq to Sql to work with the Entity Framework. This extension method has a dependency on the Like() method of SqlMethods, which is Linq to Sql specific. What I really like about this extension method is that it allows me to dynamically construct a Sql Like statement on any object at runtime, by simply passing in a property name (as string) and a query clause (also as string). Such an extension method is very convenient for using grids like flexigrid or jqgrid. Here is the Linq to Sql version (taken from this tutorial: http://www.codeproject.com/KB/aspnet/MVCFlexigrid.aspx): public static IQueryable<T> Like<T>(this IQueryable<T> source, string propertyName, string keyword) { var type = typeof(T); var property = type.GetProperty(propertyName); var parameter = Expression.Parameter(type, "p"); var propertyAccess = Expression.MakeMemberAccess(parameter, property); var constant = Expression.Constant("%" + keyword + "%"); var like = typeof(SqlMethods).GetMethod("Like", new Type[] { typeof(string), typeof(string) }); MethodCallExpression methodExp = Expression.Call(null, like, propertyAccess, constant); Expression<Func<T, bool>> lambda = Expression.Lambda<Func<T, bool>>(methodExp, parameter); return source.Where(lambda); } With this extension method, I can simply do the following: someList.Like("FirstName", "mike"); or anotherList.Like("ProductName", "widget"); Is there an equivalent way to do this with Entity Framework? Thanks in advance.

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  • Is it okay to implement reference counting through composition?

    - by Billy ONeal
    Most common re-usable reference counted objects use private inheritance to implement re-use. I'm not a huge fan of private inheritance, and I'm curious if this is an acceptable way of handling things: class ReferenceCounter { std::size_t * referenceCount; public: ReferenceCounter() : referenceCount(NULL) {}; ReferenceCounter(ReferenceCounter& other) : referenceCount(other.referenceCount) { if (!referenceCount) { referenceCount = new std::size_t(1); other.referenceCount = referenceCount; } else { ++(*referenceCount); } }; ReferenceCounter& operator=(const ReferenceCounter& other) { ReferenceCounter temp(other); swap(temp); return *this; }; void swap(ReferenceCounter& other) { std::swap(referenceCount, other.referenceCount); }; ~ReferenceCounter() { if (referenceCount) { --(*referenceCount); if (!*referenceCount) delete referenceCount; } }; operator bool() const { return referenceCount && (*referenceCount != 0); }; }; class SomeClientClass { HANDLE someHandleThingy; ReferenceCounter objectsStillActive; public: SomeClientClass() { //Construct handle thingy } ~SomeClientClass() { if (objectsStillActive) return; //Release resources }; }; or are there subtle problems with this I'm not seeing?

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  • Jquery Json dynamic variable name generation

    - by PlanetUnknown
    I make a jquery .ajax call and I'm expecting a json result. The catch is, if there are say 5 authors, I'll get author_details_0, author_details_1, author_details_2, etc.... How can I dynamically construct the name of the variable to retrieve from json ? I don't know how many authors I'll get, there could be hundreds. $.ajax({ type: "POST", url: "/authordetails/show_my_details/", data: af_pTempString, dataType: "json", beforeSend: function() { }, success: function(jsonData) { console.log("Incoming from backend : " + jsonData.toSource()); if(jsonData.AuthorCount) { console.log("Number of Authors : " + jsonData.AuthorCount); for (i = 0; i < jsonData.AuthorCount; i++) { temp = 'author_details_' + i; <-------------------This is the name of the variable I'm expecting. console.log("Farm information : " + eval(jsonData.temp) ); <----- This doesn't work, how can I get jsonData.author_details_2 for example, 'coz I don't know how many authors are there, there could be hundreds. } } Please let me know if you have any idea how to solve this ! Much appreciated.

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  • ASP Button Calling JavaScript Function

    - by Steven
    I am attempting to construct my own date picker using code from several sources. Specifically, I am now attempting to have an asp:button display/hide the calendar. What am I doing wrong? myDate.ascx <%@ Control Language="vb" AutoEventWireup="false" CodeBehind="myDate.ascx.vb" Inherits="Website.myDate" %> <script language="javascript" type="text/javascript"> function toggleCalendar(myID) { var obj = document.getElementById(myID) obj.style.display = (obj.style.display == "none") ? "" : "none"; } </script> <asp:TextBox ID="dateText" runat="server" > </asp:TextBox> <asp:Button ID="dateBtn" runat="server" UseSubmitBehavior="false" Text="x" /> <asp:Calendar ID="dateCal" runat="server" > </asp:Calendar> myDate.ascx.vb Partial Public Class myDate Inherits System.Web.UI.UserControl Protected Sub Page_Load (ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 'Add OnClick event to call JavaScript to toggle calendar display' calBtn.Attributes.Add("OnClick", "toggleCalendar(" & cal.ClientID & ")") End Sub End Class HTML code for button (from browser) <input type="button" name="ctl03$calBtn" value="x" onclick="toggleCalendar(ctl03_cal);__doPostBack('ctl03$calBtn','')" id="ctl03_calBtn" />

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  • Can Castle.Windsor do automatic resolution of concrete types

    - by Anthony
    We are evaluating IoC containers for C# projects, and both Unity and Castle.Windsor are standing out. One thing that I like about Unity (NInject and StructureMap also do this) is that types where it is obvious how to construct them do not have to be registered with the IoC Container. Is there way to do this in Castle.Windsor? Am I being fair to Castle.Windsor to say that it does not do this? Is there a design reason to deliberately not do this, or is it an oversight, or just not seen as important or useful? I am aware of container.Register(AllTypes... in Windsor but that's not quite the same thing. It's not entirely automatic, and it's very broad. To illustrate the point, here are two NUnit tests doing the same thing via Unity and Castle.Windsor. The Castle.Windsor one fails. : namespace SimpleIocDemo { using NUnit.Framework; using Castle.Windsor; using Microsoft.Practices.Unity; public interface ISomeService { string DoSomething(); } public class ServiceImplementation : ISomeService { public string DoSomething() { return "Hello"; } } public class RootObject { public ISomeService SomeService { get; private set; } public RootObject(ISomeService service) { SomeService = service; } } [TestFixture] public class IocTests { [Test] public void UnityResolveTest() { UnityContainer container = new UnityContainer(); container.RegisterType<ISomeService, ServiceImplementation>(); // Root object needs no registration in Unity RootObject rootObject = container.Resolve<RootObject>(); Assert.AreEqual("Hello", rootObject.SomeService.DoSomething()); } [Test] public void WindsorResolveTest() { WindsorContainer container = new WindsorContainer(); container.AddComponent<ISomeService, ServiceImplementation>(); // fails with exception "Castle.MicroKernel.ComponentNotFoundException: // No component for supporting the service SimpleIocDemo.RootObject was found" // I could add // container.AddComponent<RootObject>(); // but that approach does not scale RootObject rootObject = container.Resolve<RootObject>(); Assert.AreEqual("Hello", rootObject.SomeService.DoSomething()); } } }

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  • Is it possible to read data that has been separately copied to the Android sd card without having ro

    - by icecream
    I am developing an application that needs to access data on the sd card. When I run on my development device (an odroid with Android 2.1) I have root access and can construct the path using: File sdcard = Environment.getExternalStorageDirectory(); String path = sdcard.getAbsolutePath() + File.separator + "mydata" File data = new File(path); File[] files = data.listFiles(new FilenameFilter() { @Override public boolean accept(File dir, String filename) { return filename.toLowerCase().endsWith(".xyz"); }}); However, when I install this on a phone (2.1) where I do not have root access I get files == null. I assume this is because I do not have the right permissions to read the data from the sd card. I also get files == null when just trying to list files on /sdcard. So the same applies without my constructed path. Also, this app is not intended to be distributed through the app store and is needs to use data copied separately to the sd card so this is a real use-case. It is too much data to put in res/raw (I have tried, it did not work). I have also tried adding: <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> to the manifest, even though I only want to read the sd card, but it did not help. I have not found a permission type for reading the storage. There is probably a correct way to do this, but I haven't been able to find it. Any hints would be useful.

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  • Is there an algorithm to securely split a message into x parts requiring at least y parts to reassem

    - by Aaron
    Is there an algorithm to securely split a message into x parts requiring at least y parts to reassemble? Obviously, y <= x. An example: Say that I have a secret message that I only want to be read in the event of my death. As a way to ensure this, I give a fraction of the message to ten friends. Now, I can't guaranty that all my friends will be able to put their messages together to recover the original. So, I construct each message fraction in such a way so as to only require any 5 friends to put their parts together to reconstruct the whole. However, owning less than 5 parts will not give anything away about the message, except possibly the length. My question is, is this possible? What algorithms might I look at to accomplish this? Clarification edit: The important part of this is the cryptographic strength. An attacker should not be able to recover the message, either in whole or in part with less than y parts.

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  • WCF contracts - namespaces and SerializationExceptions

    - by qntmfred
    I am using a third party web service that offers the following calls and responses http://api.athirdparty.com/rest/foo?apikey=1234 <response> <foo>this is a foo</foo> </response> and http://api.athirdparty.com/rest/bar?apikey=1234 <response> <bar>this is a bar</bar> </response> This is the contract and supporting types I wrote [ServiceContract] [XmlSerializerFormat] public interface IFooBarService { [OperationContract] [WebGet( BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Xml, UriTemplate = "foo?key={apikey}")] FooResponse GetFoo(string apikey); [OperationContract] [WebGet( BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Xml, UriTemplate = "bar?key={apikey}")] BarResponse GetBar(string apikey); } [XmlRoot("response")] public class FooResponse { [XmlElement("foo")] public string Foo { get; set; } } [XmlRoot("response")] public class BarResponse { [XmlElement("bar")] public string Bar { get; set; } } and then my client looks like this static void Main(string[] args) { using (WebChannelFactory<IFooBarService> cf = new WebChannelFactory<IFooBarService>("thirdparty")) { var channel = cf.CreateChannel(); FooResponse result = channel.GetFoo("1234"); } } When I run this I get the following exception Unable to deserialize XML body with root name 'response' and root namespace '' (for operation 'GetFoo' and contract ('IFooBarService', 'http://tempuri.org/')) using XmlSerializer. Ensure that the type corresponding to the XML is added to the known types collection of the service. If I comment out the GetBar operation from IFooBarService, it works fine. I know I'm missing an important concept here - just don't know quite what to look for. What is the proper way to construct my contract types, so that they can be properly deserialized?

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  • Design pattern to keep track UITableView rows correspondance to underlying data in constant time.

    - by DenNukem
    When my model changes I want to animate changes in UITableView by inserting/deleting rows. For that I need to know the ordinal of the given row (so I can construct NSIndexPath), which I find hard to do in better-than-linear time. For example, consider that I have a list of addressbook entries which are manualy sorted by the user, i.e. there is no ordering "key" that represents the sort order. There is also a corresponding UITableView that shows one row per addressbook entry. When UITableView queries the datasource I query the NSMUtableArray populated with my entries and return required data in constant time for each row. However, if there is a change in underlying model I am getting a notification "Joe Smith, id#123 has been removed". Now I have a dilemma. A naive approach would be to scan the array, determine the index at which Joe Smith is and then ask UITableView to remove that precise row from the view, also removing it form the array. However, the scan will take linear time to finish. Now I could have an NSDictionary which allows me to find Joe Smith in constant time, but that doesn't do me a lot of good because I still need to find his ordinal index within the array in order to instruct UITableView to remove that row, which is again a linear search. I could further decide to store each object's ordinal inside the object itself to make it constant, but it will become outdated after first such update as all subsequent index values will have changed due to removal of an object. So what is the correct design pattern to accurately reflect model changes in the UITableView in costant (or at least logarithmic) time?

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  • What is the best way to translate this recursive python method into Java?

    - by Simucal
    In another question I was provided with a great answer involving generating certain sets for the Chinese Postman Problem. The answer provided was: def get_pairs(s): if not s: yield [] else: i = min(s) for j in s - set([i]): for r in get_pairs(s - set([i, j])): yield [(i, j)] + r for x in get_pairs(set([1,2,3,4,5,6])): print x This will output the desire result of: [(1, 2), (3, 4), (5, 6)] [(1, 2), (3, 5), (4, 6)] [(1, 2), (3, 6), (4, 5)] [(1, 3), (2, 4), (5, 6)] [(1, 3), (2, 5), (4, 6)] [(1, 3), (2, 6), (4, 5)] [(1, 4), (2, 3), (5, 6)] [(1, 4), (2, 5), (3, 6)] [(1, 4), (2, 6), (3, 5)] [(1, 5), (2, 3), (4, 6)] [(1, 5), (2, 4), (3, 6)] [(1, 5), (2, 6), (3, 4)] [(1, 6), (2, 3), (4, 5)] [(1, 6), (2, 4), (3, 5)] [(1, 6), (2, 5), (3, 4)] This really shows off the expressiveness of Python because this is almost exactly how I would write the pseudo-code for the algorithm. I especially like the usage of yield and and the way that sets are treated as first class citizens. However, there in lies my problem. What would be the best way to: 1.Duplicate the functionality of the yield return construct in Java? Would it instead be best to maintain a list and append my partial results to this list? How would you handle the yield keyword. 2.Handle the dealing with the sets? I know that I could probably use one of the Java collections which implements that implements the Set interface and then using things like removeAll() to give me a set difference. Is this what you would do in that case? Ultimately, I'm looking to reduce this method into as concise and straightforward way as possible in Java. I'm thinking the return type of the java version of this method will likely return a list of int arrays or something similar. How would you handle the situations above when converting this method into Java?

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  • sending a selected value from a dropdownlist to a servlet with xhr

    - by kawtousse
    I am trying to send the clicked value of a dropdown list to my servlet to run a SQL query using the value received. To do it I am using Ajax like that: function showProject(prj) { xmlhttp = GetXmlHttpObject(); if (xmlhttp == null) { alert ("Browser does not support HTTP Request"); return; } var url = "ServletxmlGenerator.java"; idprj = prj.options[prj.selectedIndex].value; url = url + "?idprj=" + idprj; xmlhttp.onreadystatechange = stateChanged; xmlhttp.open("GET",url,true); xmlhttp.send(null); } The servlet when String projectcode=(String) request.getParameter("idprj"); returns null. When I select a value from the JSP that construct the dropdown list and from which the function showProject is handled the same thing is happned. It returns always null. So the parameter(idprj) is not passed anyway. How can I handle with this. I need to send the selected value to the servlet to run my SQL query.

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  • Reading email address from contacts fails with weird memory issue

    - by CapsicumDreams
    Hi all, I'm stumped. I'm trying to get a list of all the email address a person has. I'm using the ABPeoplePickerNavigationController to select the person, which all seems fine. I'm setting my ABRecordRef personDealingWith; from the person argument to - (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker shouldContinueAfterSelectingPerson:(ABRecordRef)person property:(ABPropertyID)property identifier:(ABMultiValueIdentifier)identifier { and everything seems fine up till this point. The first time the following code executes, all is well. When subsequently run, I can get issues. First, the code: // following line seems to make the difference (issue 1) // NSLog(@"%d", ABMultiValueGetCount(ABRecordCopyValue(personDealingWith, kABPersonEmailProperty))); // construct array of emails ABMultiValueRef multi = ABRecordCopyValue(personDealingWith, kABPersonEmailProperty); CFIndex emailCount = ABMultiValueGetCount(multi); if (emailCount 0) { // collect all emails in array for (CFIndex i = 0; i < emailCount; i++) { CFStringRef emailRef = ABMultiValueCopyValueAtIndex(multi, i); [emailArray addObject:(NSString *)emailRef]; CFRelease(emailRef); } } // following line also matters (issue 2) CFRelease(multi); If compiled as written, the are no errors or static analysis problems. This crashes with a *** -[Not A Type retain]: message sent to deallocated instance 0x4e9dc60 error. But wait, there's more! I can fix it in either of two ways. Firstly, I can uncomment the NSLog at the top of the function. I get a leak from the NSLog's ABRecordCopyValue every time through, but the code seems to run fine. Also, I can comment out the CFRelease(multi); at the end, which does exactly the same thing. Static compilation errors, but running code. So without a leak, this function crashes. To prevent a crash, I need to haemorrhage memory. Neither is a great solution. Can anyone point out what's going on?

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  • JavaEE : "Access to default session denied" when sending mail using smtp.gmail.com

    - by Harry Pham
    I am trying to write email authentication feature for my website and I encounter some issues. I got java.lang.SecurityException: Access to default session denied, when I try to do Session.getDefaultInstance. Here are my codes: private static final String SMTP_HOST_NAME = "smtp.gmail.com"; private static final String SMTP_PORT = "465"; private static final String emailSubjectTxt = "Email Confirmation"; private static final String emailFromAddress = "[email protected]"; private static final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory"; ... String sendTo = "[email protected]"; boolean debug = true; Properties props = new Properties(); props.put("mail.smtp.host", SMTP_HOST_NAME); props.put("mail.smtp.auth", "true"); props.put("mail.debug", "true"); props.put("mail.smtp.port", SMTP_PORT); props.put("mail.smtp.socketFactory.port", SMTP_PORT); props.put("mail.smtp.socketFactory.class", SSL_FACTORY); props.put("mail.smtp.socketFactory.fallback", "false"); //It dies at the next line Session session = Session.getDefaultInstance(props, new javax.mail.Authenticator() { @Override protected PasswordAuthentication getPasswordAuthentication() { return new PasswordAuthentication("myUserName", "myPassword"); } }); session.setDebug(debug); //Set the FROM address Message msg = new MimeMessage(session); InternetAddress addressFrom = new InternetAddress(emailFromAddress); msg.setFrom(addressFrom); //Set the TO address InternetAddress[] addressTo = new InternetAddress[1]; addressTo[0] = new InternetAddress(sendTo); msg.setRecipients(Message.RecipientType.TO, addressTo); //Construct the content of the email confirmation String message = "Test Content" // Setting the Subject and Content Type msg.setSubject(emailSubjectTxt); msg.setContent(message, "text/plain"); Transport.send(msg);

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  • MySQL - NULL value check and Dynamic SQL inside stored procedure

    - by Mithun P
    DROP PROCEDURE IF EXISTS HaveSomeFun; CREATE PROCEDURE HaveSomeFun(user_id CHAR(50),house_id CHAR(50),room_id CHAR(50),fun_text TEXT,video_url CHAR(100)) BEGIN DECLARE query_full TEXT; SET @fields_part = 'INSERT INTO fun(FunKey,UserKey,FunBody,LastModified'; SET @values_part = CONCAT(') VALUES( NewBinKey(), KeyToBin(\"', user_id, '\"), \"', fun_text, '\", NOW() '); IF (house_id) THEN SET @fields_part = CONCAT(@fields_part, ', HouseKey'); SET @values_part = CONCAT(@values_part, ', KeyToBin(\'', house_id, '\')'); END IF; IF (room_id) THEN SET @fields_part = CONCAT(@fields_part, ', RoomKey'); SET @values_part = CONCAT(@values_part, ', KeyToBin(\'', room_id, '\')'); END IF; IF (video_url IS NOT NULL) THEN SET @fields_part = CONCAT(@fields_part, ', VideoURL'); SET @values_part = CONCAT(@values_part, ', "', video_url, '"'); END IF; SET query_full = CONCAT(@fields_part, @values_part, ' );'); SET @query_full = query_full; PREPARE STMT FROM @query_full; EXECUTE STMT; SELECT query_full; END; And CALL HaveSomeFun('29B455DE-A9BC-102D-9C16-00163EEDFCFC', '', 'F82C47A8-64DE-11DF-9D7E-0026B9481364', 'Jokes apart', ''); will construct the below string in the variable query_full INSERT INTO fun(FunKey,UserKey,FunBody,LastModified, VideoURL) VALUES( NewBinKey(), KeyToBin("29B455DE-A9BC-102D-9C16-00163EEDFCFC"), "Jokes apart", NOW() , "" ); But I need to get INSERT INTO fun(FunKey,UserKey,FunBody,LastModified, RoomKey, VideoURL) VALUES( NewBinKey(), KeyToBin("29B455DE-A9BC-102D-9C16-00163EEDFCFC"), "Jokes apart", NOW() , KeyToBin('F82C47A8-64DE-11DF-9D7E-0026B9481364'), "" ); Something is missing in the check IF (room_id) THEN. But I cannot impose IF (room_id IS NOT NULL) THEN since it will create KeyToBin('') and RoomKey is foreign key , KeyToBin('') will produce an invalid RoomKey. Any Idea?

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  • Error in creating trigger using PHP script.. Please help!!!! Geeks

    - by Parth
    I've been successful in creating a simple trigger with a PHP script. The problem comes when I have to use "DELIMITER" in my trigger creating because I have nested if/then statements. For example, the following DOES work: $sql = 'CREATE TRIGGER `database`.`detail` BEFORE INSERT on `database`.`vibez_detail` FOR EACH ROW set @a=new.realtime_value'; $junk = mysqli_query($link, $sql); However, if I need to use "DELIMITER" I get errors galore. Here's what works if I go to the MySQL client at the server: DELIMITER $$; DROP TRIGGER `database`.`detail`$$ CREATE TRIGGER `database`.`detail` BEFORE INSERT on `database`.`vibez_detail` FOR EACH ROW BEGIN set new.data_rate = 69; insert into alarm_trips_parent values (null, new.data_rate, 6969, now()); set @tripped_time = now(); set @tripped:=true; end if; end if; END$$ DELIMITER ;$$ How can I construct the PHP code to get this to work? Seems the mysqli_query($link, $sql) chokes as soon as I put "DELIMITER" in the $sql variable. I get the following error when I attempt to do so: Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DELIMITER //; CREATE TRIGGER `database`.`detail` BEFORE INS' at line 1 Even The concept for using mysqli_multi_query(); didn't worked for me.... :(

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  • algorithm || method to write prog

    - by fatai
    I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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