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• Please suggest other ways of communicating between server & client.

  - by Geo

  I'm writing a TCP chat server ( programming language does not mather ). It's a school project for my nephew, so it won't be released, and all questions I'm asking are just for my knowledge :). . Some of the things it will support: chatting between users ( doh ), it will be multithreaded sending each other files I know I could easily get away with all the stuff above if I go with serialization, and just send objects from client to server and back. But, if I do that, it will be limited to a specific programming language ( meaning clients written in other programming languages may not be able to deserialize the objects ). What would be the way to go so that other clients written in other languages could be supported? One way to go, off the top of my head, would be to go in this direction: the server & the client communicate by sending messages & chunks ( in lieu of other names ). Here's what I mean by this: every time the client/server wants to send something ( text message or file ) it will first send a simple text message ( newline terminated ) with the number of the chunks it will send. Example: command 4,20,30,40,50 Where command would be something like instant-message or file,4 would be the number of chunks to be sent, 20 would be the size in bytes of the first chunk, 30 of the 2nd, and so forth. after the message was sent, the client/server will start sending chunks ( of sizes mentioned in the sent message ). What do you think about implementing the client/server communication this way? What better options are there?

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• How to retrive user input data entered tab bar View Controller when application start in iphone app

  - by TechFusion

  Hello, I have created window based application. Tab bar controller as root controller and it has three tabs. One Tab has Labels and TextFiled inputs like Name, Username and Password. I am looking to store this text filed inputs when user enters and able retrieve in other tabs. Previously I have set key for different text fields and setobject:withkey task and able to retrive text filed values in same view Controller [[NSUserDefaults standardUserDefaults] stringForKey:key] task. Now I am looking to create database which has different objects and each objects has data values of different Text Field inputs that I can access in whole application. like DatabaseName - Object1 - Name, Username & Password - Object2 - Name, Username & Password Something like structure in Normal C so it would be easy to retrieve data. I am looking NSUserDefaults Class and User Defaults Programming Topics in Cocoa(http://developer.apple.com/iPhone/library/documentation/Cocoa/Conceptual/UserDefaults/UserDefaults.html#//apple_ref/doc/uid/10000059-BCIDJFHD). Also Referring Archives and Serialization Programming guide(http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/Archiving/Archiving.html#//apple_ref/doc/uid/10000047i). Which method i need to use to create such type of database ? Thanks,

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• Event Dispatching, void pointer and alternatives

  - by PeeS

  i have my event dispatching / handling functionality working fine, but there is one issue that i need to resolve. Long story short, here are the details. // The event structure struct tEventMessage { // Type of the event int Type; // (void*) Allows those to be casted into per-Type objects void *pArgument1; void *pArgument2; }; I am sending events from different modules in my engine by using the above structure, which requires a pointer to an argument. All messages are queued, and then dispatched on the next ::Tick(). It works fine, untill i try to send something that doesn't exist in next ::Tick, for example: When a mouse click is being handled, it calculates the click coordinates in world space. This is being sent with a pointer to a vector representing that position, but after my program quits that method, this pointer gets invalid obviously, cause local CVector3 is destructed: CVector2 vScreenSpacePosition = vAt; CVector3 v3DPositionA = CVector3(0,0,0); CVector3 v3DPositionB = CVector3(0,0,0); // Screen space to World space calculation for depth zNear v3DPositionA = CMath::UnProject(vScreenSpacePosition, m_vScreenSize, m_Level.GetCurrentCamera()->getViewMatrix(), m_Level.GetCurrentCamera()->getProjectionMatrix(), -1.0 ); // Screen space to World space calculation for depth zFar v3DPositionB = CMath::UnProject(vScreenSpacePosition, m_vScreenSize, m_Level.GetCurrentCamera()->getViewMatrix(), m_Level.GetCurrentCamera()->getProjectionMatrix(), 1.0); // Send zFar position and ScreenSpace position to the handlers // Obviously both vectors won't be valid after this method quits.. CEventDispatcher::Get()->SendEvent(CIEventHandler::EVENT_SYSTEM_FINGER_DOWN, static_cast<void*>(&v3DPositionB), static_cast<void*>(&vScreenSpacePosition)); What i want to ask is, if there is any chance i could make my tEventMessage more 'template', so i can handle sending objects like in the above situation + use what is already implemented? Can't figure it out at the moment.. What else can be done here to allow me to pass some locally available data ? Please can somebody shed a bit of light on this please?

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• Error with threads during automatic testing on TeamCity 5

  - by yeyeyerman

  Hello, I'm having some problems executing the tests of the application I'm developing. All the tests execute normally with ReSharper and in NCover. However, the execution of one of these tests in TeamCity is generating an error. This test initializes two objects, the object under test and a simulator of a real object. Both objects will communicate throug a serial link in a representation of the real scenario. ObjectSimulator r_simulator = new ObjectSimulator(...); ObjectDriver r_driver = new ObjectDriver(...); Assert.IsTrue(r_driver.Connect() == ErrorCode.Success); The simulator just do the following in the constructor public class ObjectSimulator { ... public ObjectSimulator() { // serial port configuration m_port = new SerialPort(); m_port.DataReceived += DataReceivedEvent; } ... } The main object has two threads. The main thread of the application and a timer to refresh a watchdog timer in the real object. public ErrorCode Connect() { ... StartSynchroTimer(); Thread.Sleep(4); // to check if the timer is working properly ... } The problem is comming from the Thread.Sleep() call, as when I remove it everything works. It seems like the ObjectSimulator also sleeps and doesn't receive the DataReceived event. How can I resolve this issue?

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• Entity Framework Decorator Pattern

  - by Anthony Compton

  In my line of business we have Products. These products can be modified by a user by adding Modifications to them. Modifications can do things such as alter the price and alter properties of the Product. This, to me, seems to fit the Decorator pattern perfectly. Now, envision a database in which Products exist in one table and Modifications exist in another table and the database is hooked up to my app through the Entity Framework. How would I go about getting the Product objects and the Modification objects to implement the same interface so that I could use them interchangeably? For instance, the kind of things I would like to be able to do: Given a Modification object, call .GetNumThings(), which would then return the number of things in the original object, plus or minus the number of things added by the modification. This question may be stemming from a pretty serious lack of exposure to the nitty-gritty of EF (all of my experience so far has been pretty straight-forward LOB Silverlight apps), and if that's the case, please feel free to tell me to RTFM. Thanks in advance!

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• REST design: what verb and resource name to use for a filtering service

  - by kabaros

  I am developing a cleanup/filtering service that has a method that receives a list of objects serialized in xml, and apply some filtering rules to return a subset of those objects. In a REST-ful service, what verb shall I use for such a method? I thought that GET is a natural choice, but I have to put the serialized XML in the body of the request which works but feels incorrect. The other verbs don't seem to fit semantically. What is a good way to define that Service interface? Naming the resource /Cleanup or /Filter seems weird mainly because in the examples I see online, it is always a name rather than a verb being used for resource name. Am I right to feel that REST services are better suited for CRUD operations and you start bending the rules in situations like this service? If yes, am I then making a wrong architectural choice. I've pushed to develop this service in REST-ful style (as opposed to SOAP) for simplicity, but such awkward cases happen a lot and make me feel like I am missing something. Either choosing REST where it shouldn't be used or may be over-thinking some stuff that doesn't really matter? In that case, what really matters?

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• Django: Storing ordered, arbitrary references

  - by Sarah

  I'm new to Django, and I'm not sure what I want is possible: I have a number of items that I want each AppUser (extended User model) to be able to reference. That is, given an AppUser, I want to be able to extract its list of items in the way that AppUser has chosen to order them. In general, these items would actually be references to something else in the database, and this led me to one possible solution: Store the keys for the given objects in a CommaSeparatedIntegerField in AppUser. This way, a user could have stored {7, 3, 232, 42, 1} in their items field and both the references and their preferred order would be stored. However, this feels hacky. Since most db backends store CommaSeparatedIntegerField as a VARCHAR internally, the user is not only limited by a number of objects, but also the number of digits in their chosen items. Eg. "you may store 10 items if you choose items with itemID < 10, but only 5 items if 10 < itemID < 100". Is there a better way to do this?

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• Python class structure ... prep() method?

  - by Adam Nelson

  We have a metaclass, a class, and a child class for an alert system: class AlertMeta(type): """ Metaclass for all alerts Reads attrs and organizes AlertMessageType data """ def __new__(cls, base, name, attrs): new_class = super(AlertMeta, cls).__new__(cls, base, name, attrs) # do stuff to new_class return new_class class BaseAlert(object): """ BaseAlert objects should be instantiated in order to create new AlertItems. Alert objects have classmethods for dequeue (to batch AlertItems) and register (for associated a user to an AlertType and AlertMessageType) If the __init__ function recieves 'dequeue=True' as a kwarg, then all other arguments will be ignored and the Alert will check for messages to send """ __metaclass__ = AlertMeta def __init__(self, **kwargs): dequeue = kwargs.pop('dequeue',None) if kwargs: raise ValueError('Unexpected keyword arguments: %s' % kwargs) if dequeue: self.dequeue() else: # Do Normal init stuff def dequeue(self): """ Pop batched AlertItems """ # Dequeue from a custom queue class CustomAlert(BaseAlert): def __init__(self,**kwargs): # prepare custom init data super(BaseAlert, self).__init__(**kwargs) We would like to be able to make child classes of BaseAlert (CustomAlert) that allow us to run dequeue and to be able to run their own __init__ code. We think there are three ways to do this: Add a prep() method that returns True in the BaseAlert and is called by __init__. Child classes could define their own prep() methods. Make dequeue() a class method - however, alot of what dequeue() does requires non-class methods - so we'd have to make those class methods as well. Create a new class for dealing with the queue. Would this class extend BaseAlert? Is there a standard way of handling this type of situation?

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• Elements of a Java Object Array are created but without correct names

  - by Greenhouse Gases

  Hi all Im having rather an annoying problem. I have a class called Person and a class called Event which serve to create objects to be used for competitors that compete in a certain event. When I add a competitor thats fine and the GUI list updates accordingly, however when I add an event the element in the array does not take on the value of the instance variable name in the class Event and so the GUI does not show the event name, though it is being added in the array correctly. How can I make it so that the event object in each element of the listOfEvents array (which is an array of event objects) has the name of the event. I should add this is for university though this isnt the part for which we will be assessed, it is somethign i have come across and due to not being able to see the code for the GUI, I've hit the proverbial brick wall. I wont include the whole load of code Ive been writing but hopefully my description and snippets below will suffice. Any advice I would appreciate greatly. No doubt I have overlooked something simple! Many thanks. listOfEvents is declared as: Event[] listOfEvents = new Event[20]; A snippet from the Event class: public class Event { String name; Person[] participants = new Person[10]; // array of competitors for the event public Event(String name) { this.name = name; } } and its use in the addEvent method (p is a global variable): public void addEvent(String eventName) { listOfEvents[p] = new Event(eventName); p++; }

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• C++ privately contructed class

  - by Nona Urbiz

  How can I call a function and keep my constructor private? If I make the class static, I need to declare an object name which the compiler uses to call the constructor, which it cannot if the constructor is private (also the object would be extraneous). Here is the code I am attempting to use (it is not compilable): I want to keep the constructor private because I will later be doing a lot of checks before adding an object, modifying previous objects when all submitted variables are not unique rather than creating new objects. #include <iostream> #include <fstream> #include <regex> #include <string> #include <list> #include <map> using namespace std; using namespace tr1; class Referral { public: string url; map<string, int> keywords; static bool submit(string url, string keyword, int occurrences) { //if(Referrals.all.size == 0){ // Referral(url, keyword, occurrences); //} } private: list<string> urls; Referral(string url, string keyword, int occurrences) { url = url; keywords[keyword] = occurrences; Referrals.all.push_back(this); } }; struct All { list<Referral> all; }Referrals; int main() { Referral.submit("url", "keyword", 1); }

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• Implementing IEnumeralbe on Non-Listed Items

  - by Stacey

  I have a class that contains a static number of objects. This class needs to be frequently 'compared' to other classes that will be simple List objects. public partial class Sheet { public Item X{ get; set; } public Item Y{ get; set; } public Item Z{ get; set; } } the items are obviously not going to be "X" "Y" "Z", those are just generic names for example. The problem is that due to the nature of what needs to be done, a List won't work; even though everything in here is going to be of type Item. It is like a checklist of very specific things that has to be tested against in both code and runtime. This works all fine and well; it isn't my issue. My issue is iterating it. For instance I want to do the following... List<Item> UncheckedItems = // Repository Logic Here. UncheckedItems contains all available items; and the CheckedItems is the Sheet class instance. CheckedItems will contain items that were moved from Unchecked to Checked; however due to the nature of the storage system, items moved to Checked CANNOT be REMOVED from Unchecked. I simply want to iterate through "Checked" and remove anything from the list in Unchecked that is already in "Checked". So naturally, that would go like this with a normal list. foreach(Item item in Unchecked) { if( Checked.Contains(item) ) Unchecked.Remove( item ); } But since "Sheet" is not a 'List', I cannot do that. So I wanted to implement IEnumerable so that I could. Any suggestions? I've never implemented IEnumerable directly before and I'm pretty confused as to where to begin.

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• Any way to define getters for lazy variables in Javascript arrays?

  - by LLer

  I'm trying to add elements to an array that are lazy-evaluated. This means that the value for them will not be calculated or known until they are accessed. This is like a previous question I asked but for objects. What I ended up doing for objects was Object.prototype.lazy = function(var_name, value_function) { this.__defineGetter__(var_name, function() { var saved_value = value_function(); this.__defineGetter__(var_name, function() { return saved_value; }); return saved_value; }); } lazy('exampleField', function() { // the code that returns the value I want }); But I haven't figured out a way to do it for real Arrays. Arrays don't have setters like that. You could push a function to an array, but you'd have to call it as a function for it to return the object you really want. What I'm doing right now is I created an object that I treat as an array. Object.prototype.lazy_push = function(value_function) { if(!this.length) this.length = 0; this.lazy(this.length++, value_function); } So what I want to know is, is there a way to do this while still doing it on an array and not a fake array?

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• Adding property:value pairs from GooglemapsAPI to an existing json/javascript object

  - by Rockinelle

  I am trying to create a script that finds the closest store/location to a customer using googlemapsAPI. So I've got a json object which is a collection of store objects. Using Jquery's .each to iterate through that object, I am grabbing the driving time from the customer to each store. If it finds the directions, It copies the duration of the drive which is an object with the time in seconds and a human readable value. That appears to work, however when I try to sort through all of those store objects with the drivetime added, I cannot read the object copied from google. If I console.log the whole object, 'closest_store', It shows the values I'm looking for. When I try to read the values directly via closest_store.driveTime, Firebug is outputting undefined in the console. What am I missing here? $.getJSON('<?php echo Url::base() ?>oldservices/get_locations', {}, function(data){ $.each(data, function(index, value) { var end = data[index].address; var request = { origin: start, destination: end, travelMode: google.maps.DirectionsTravelMode.DRIVING }; directionsService.route(request, function(response, status) { //console.log(response); if (status == google.maps.DirectionsStatus.OK) { value.driveTime = response.trips[0].routes[0].duration.value; //console.log(response.trips[0].routes[0].duration.value); }; }); }); var closest_store; $.each(data, function(index, current_store) { if (index == 0) { closest_store = current_store; } else if (current_store.driveTime.value < closest_store.driveTime.value) { closest_store = value }; console.log(current_store.driveTime); } ) });

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• Object model design choice

  - by spinon

  I am currently working on a ASP.NET MVC reporting application using C#. This is a redesign from a PHP application that was just initially thrown together and is now starting to gain some more traction. SowWe are in the process of reworking the backend to have a more OO approach. One of the descisions I am currently wrestling with is how to structure the domain objects. Since 95% of the site is readonly I am not sure if the typical approaches are practical. Should I create domain objects for the primary pieces of the application (ticket, assignment, assignee) and then create static methods off of these areas to pull the reporting data? Or should I just skip that part and create the chart data classes and have some get method off of these classes? It's not a real big application and currenlty I am the only one developing on it. But I feel torn as to which approach. I feel that the first one is the better choice but maybe overkill given that the majority of uses is for aggregate reporting. Anybody have some good insight on why I should go one way or another?

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• Help Needed Finding a Programmer

  - by ssean

  Good Morning, I am trying to find a programmer to code a piece of custom software for my business. I plan on using this software to manage my business, and possibly sell it to other companies (in the same industry) at a later date. I've never hired a programmer before, so I'm not sure what to expect or where to begin. I know exactly what features I need, and how I want it laid out, I just need someone who can take my ideas and make it happen. This software will be used to manage customer information, and keep track of orders. What I think I need: * SQL Server or similar database that will be located at our office. * Desktop Application, that connects via LAN to the database server (cannot be browser based) * Multiple User Support (Simultaneous users accesing the system) * Needs to be scalable (currently we have 5 employees, but who knows what the future will bring) * Multi-Platform Support (Windows, Linux) I posted a job offer through elance, which seems to raise more questions than answers. How do I decide what language(s) will work best for my situation? (I have received offers for C#, Eclipse, .NET, Powerbuilder, etc. - I want to make sure that I choose the best one now, so I don't run into problems later) Does the programmer hold any rights to the software? (I plan to offer the software for sale at a later date) Any help or insight would be appreciated, and I'd be happy to clarify anything if it helps. Thanks in advance!

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• Mixing stored procedures and ORM

  - by Jason

  The company I work for develops a large application which is almost entirely based on stored procedures. We use classic ASP and SQL Server and the major part of the business logic is contained inside those stored procedures. For example, (I know, this is bad...) a single stored procedure can be used for different purposes (insert, update, delete, make some calculations, ...). Most of the time, a stored procedure is used for operations on related tables, but this is not always the case. We are planning to move to ASP.NET in a near future. I have read a lot of posts on StackOverflow recommending that I move the business logic outside the database. The thing is, I have tried to convince the people who takes the decisions at our company and there is nothing I can do to change their mind. Since I want to be able to use the advantages of object-oriented programming, I want to map the tables to actual classes. So far, my solution is to use an ORM (Entity Framework 4 or nHibernate) to avoid mapping the objects manually (mostly to retrieve the data) and use some kind of Data Access Layer to call the existing stored procedures (for saving). I want your advice on this. Do you think it is a good solution? Any ideas?

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• A data structure based on the R-Tree: creating new child nodes when a node is full, but what if I ha

  - by Tom

  I realize my title is not very clear, but I am having trouble thinking of a better one. If anyone wants to correct it, please do. I'm developing a data structure for my 2 dimensional game with an infinite universe. The data structure is based on a simple (!) node/leaf system, like the R-Tree. This is the basic concept: you set howmany childs you want a node (a container) to have maximum. If you want to add a leaf, but the node the leaf should be in is full, then it will create a new set of nodes within this node and move all current leafs to their new (more exact) node. This way, very populated areas will have a lot more subdivisions than a very big but rarely visited area. This works for normal objects. The only problem arises when I have more than maxChildsPerNode objects with the exact same X,Y location: because the node is full, it will create more exact subnodes, but the old leafs will all be put in the exact same node again because they have the exact same position -- resulting in an infinite loop of creating more nodes and more nodes. So, what should I do when I want to add more leafs than maxChildsPerNode with the exact same position to my tree? PS. if I failed to explain my problem, please tell me, so I can try to improve the explanation.

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• Is it okay to violate the principle that collection properties should be readonly for performance?

  - by uriDium

  I used FxCop to analyze some code I had written. I had exposed a collection via a setter. I understand why this is not good. Changing the backing store when I don't expect it is a very bad idea. Here is my problem though. I retrieve a list of business objects from a Data Access Object. I then need to add that collection to another business class and I was doing it with the setter method. The reason I did this was that it is going to be faster to make an assignment than to insert hundreds of thousands of objects one at a time to the collection again via another addElement method. Is it okay to have a getter for a collection in some scenarios? I though of rather having a constructor which takes a collection? I thought maybe I could pass the object in to the Dao and let the Dao populate it directly? Are there any other better ideas?

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• Potential Django Bug In QuerySet.query?

  - by Mike

  Disclaimer: I'm still learning Django, so I might be missing something here, but I can't see what it would be... I'm running Python 2.6.1 and Django 1.2.1. (InteractiveConsole) >>> from myproject.myapp.models import * >>> qs = Identifier.objects.filter(Q(key="a") | Q(key="b")) >>> print qs.query SELECT `app_identifier`.`id`, `app_identifier`.`user_id`, `app_identifier`.`key`, `app_identifier`.`value` FROM `app_identifier` WHERE (`app_identifier`.`key` = a OR `app_identifier`.`key` = b ) >>> Notice that it doesn't put quotes around "a" or "b"! Now, I've determined that the query executes fine. So, in reality, it must be doing so. But, it's pretty annoying that printing out the query prints it wrong. Especially if I did something like this... >>> qs = Identifier.objects.filter(Q(key=") AND") | Q(key="\"x\"); DROP TABLE `app_identifier`")) >>> print qs.query SELECT `app_identifier`.`id`, `app_identifier`.`user_id`, `app_identifier`.`key`, `app_identifier`.`value` FROM `app_identifier` WHERE (`app_identifier`.`key` = ) AND OR `app_identifier`.`key` = "x"); DROP TABLE `app_identifier` ) >>> Which, as you can see, not only creates completely malformed SQL code, but also has the seeds of a SQL injection attack. Now, obviously this wouldn't actually work, for quite a number of reasons (1. The syntax is all wrong, intentionally, to show the oddity of Django's behavior. 2. Django won't actually execute the query like this, it will actually put quotes and slashes and all that in there like it's supposed to). But, this really makes debugging confusing, and it makes me wonder if something's gone wrong with my Django installation. Does this happen for you? If so/not, what version of Python and Django do you have? Any thoughts?

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• Python: Behavior of object in set operations

  - by Josh Arenberg

  I'm trying to create a custom object that behaves properly in set operations. I've generally got it working, but I want to make sure I fully understand the implications. In particular, I'm interested in the behavior when there is additional data in the object that is not included in the equal / hash methods. It seems that in the 'intersection' operation, it returns the set of objects that are being compared to, where the 'union' operations returns the set of objects that are being compared. To illustrate: class MyObject: def __init__(self,value,meta): self.value = value self.meta = meta def __eq__(self,other): if self.value == other.value: return True else: return False def __hash__(self): return hash(self.value) a = MyObject('1','left') b = MyObject('1','right') c = MyObject('2','left') d = MyObject('2','right') e = MyObject('3','left') print a == b # True print a == c # False for i in set([a,c,e]).intersection(set([b,d])): print "%s %s" % (i.value,i.meta) #returns: #1 right #2 right for i in set([a,c,e]).union(set([b,d])): print "%s %s" % (i.value,i.meta) #returns: #1 left #3 left #2 left Is this behavior documented somewhere and deterministic? If so, what is the governing principle?

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• Are there any other ways to iterate through the attributes of a custom class, excluding the in-built ones?

  - by Ricardo Altamirano

  Is there another way to iterate through only the attributes of a custom class that are not in-built (e.g. __dict__, __module__, etc.)? For example, in this code: class Terrain: WATER = -1 GRASS = 0 HILL = 1 MOUNTAIN = 2 I can iterate through all of these attributes like this: for key, value in Terrain.__dict__.items(): print("{: <11}".format(key), " --> ", value) which outputs: MOUNTAIN --> 2 __module__ --> __main__ WATER --> -1 HILL --> 1 __dict__ --> <attribute '__dict__' of 'Terrain' objects> GRASS --> 0 __weakref__ --> <attribute '__weakref__' of 'Terrain' objects> __doc__ --> None If I just want the integer arguments (a rudimentary version of an enumerated type), I can use this: for key, value in Terrain.__dict__.items(): if type(value) is int: # type(value) == int print("{: <11}".format(key), " --> ", value) this gives the expected result: MOUNTAIN --> 2 WATER --> -1 HILL --> 1 GRASS --> 0 Is it possible to iterate through only the non-in-built attributes of a custom class independent of type, e.g. if the attributes are not all integral. Presumably I could expand the conditional to include more types, but I want to know if there are other ways I'm missing.

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• Force calling the derived class implementation within a generic function in C#?

  - by Adam Hardy

  Ok so I'm currently working with a set of classes that I don't have control over in some pretty generic functions using these objects. Instead of writing literally tens of functions that essentially do the same thing for each class I decided to use a generic function instead. Now the classes I'm dealing with are a little weird in that the derived classes share many of the same properties but the base class that they are derived from doesn't. One such property example is .Parent which exists on a huge number of derived classes but not on the base class and it is this property that I need to use. For ease of understanding I've created a small example as follows: class StandardBaseClass {} // These are simulating the SMO objects class StandardDerivedClass : StandardBaseClass { public object Parent { get; set; } } static class Extensions { public static object GetParent(this StandardDerivedClass sdc) { return sdc.Parent; } public static object GetParent(this StandardBaseClass sbc) { throw new NotImplementedException("StandardBaseClass does not contain a property Parent"); } // This is the Generic function I'm trying to write and need the Parent property. public static void DoSomething<T>(T foo) where T : StandardBaseClass { object Parent = ((T)foo).GetParent(); } } In the above example calling DoSomething() will throw the NotImplemented Exception in the base class's implementation of GetParent(), even though I'm forcing the cast to T which is a StandardDerivedClass. This is contrary to other casting behaviour where by downcasting will force the use of the base class's implementation. I see this behaviour as a bug. Has anyone else out there encountered this?

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• How does git fetches commits associated to a file ?

  - by liadan

  I'm writing a simple parser of .git/* files. I covered almost everything, like objects, refs, pack files etc. But I have a problem. Let's say I have a big 300M repository (in a pack file) and I want to find out all the commits which changed /some/deep/inside/file file. What I'm doing now is: fetching last commit finding a file in it by: fetching parent tree finding out a tree inside recursively repeat until I get into the file additionally I'm checking hashes of each subfolders on my way to file. If one of them is the same as in commit before, I assume that file was not changed (because it's parent dir didn't change) then I store the hash of a file and fetch parent commit finding file again and check if hash change occurs if yes then original commit (i.e. one before parent) was changing a file And I repeat it over and over until I reach very first commit. This solution works, but it sucks. In worse case scenario, first search can take even 3 minutes (for 300M pack). Is there any way to speed it up ? I tried to avoid putting so large objects in memory, but right now I don't see any other way. And even that, initial memory load will take forever :( Greets and thanks for any help!

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• Why won't JPA delete owned entities when the owner entity loses the reference to them?

  - by Nick

  Hi! I've got a JPA entity "Request", that owns a List of Answers (also JPA entities). Here's how it's defined in Request.java: @OneToMany(cascade= CascadeType.ALL, mappedBy="request") private List<Answer> answerList; And in Answer.java: @JoinColumn(name = "request", referencedColumnName="id") @ManyToOne(optional = false) private Request request; In the course of program execution, the Request's List of Answers may have Answers added or removed from it, or the actual List object may be replaced. My problem is thus: when I merge a Request to the database, the Answer objects that used to be in the List are kept in the database -- that is, Answer objects that the Request no longer holds a reference to (indirectly, via a List) are not deleted. This is not the behaviour I desire, as if I merge a Request to the database, and then fetch it again, its Answers List may not be the same. Am I making some programming mistake? Is there an annotaion or setting that will ensure that the Answers in the database are exactly the Answers in the Request's List? A solution is to keep references to the original Answers List and then use the EntityManager to remove each old Answer before merging the Request, but it seems like there should be a cleaner way. Thank you!

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• C++ traits question

  - by duli

  I have a templated class template <typename Data> class C { ..... } In most situations, I depend on the compiler to let me substitute types for Data. I call methods foo(), goo() on objects of type Data, so what I substitute needs to provide that. I now need to substitute int and string for my Data type. I do not want to specialize because the class is already too big and would require specializing each method (with only small code change). My options (please tell me if there are more) 1) I can provide wrapper classes around int and string which implement the methods foo(), goo() etc 2) provide a traits class traits that calls foo() or goo() on objects of classes that provide foo(),goo() (these are my present substitutable classes) and specialize these classes for int and string. Questions 1) what are the relative merits of 1 vs 2? 2) My traits classes will have static methods. Can a traits class have non-static methods as well? I see most traits classes define constants in the STL. 3) Do I make the traits classes global or should I pass them in as a template parameter for class C?

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