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  • Python new-style classes and __subclasses__ function

    - by Fraser Graham
    Can somebody explain to me why this works (in Python 2.5) : class Foo(object): pass class Bar(Foo): pass print(Foo.__subclasses__()) but this doesn't : class Foo(): pass class Bar(Foo): pass print(Foo.__subclasses__()) The latter returns "AttributeError: class Foo has no attribute '__subclasses__'" but i'm not sure why. I know this is related to old-style vs. new-style classes but i'm not clear on why that would make this functionality unavailable.

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  • Java: limit to nest classes?

    - by HH
    A very poor style to code but sometimes unavoidable. It is an extreme example. So is there some limit for nesting classes? are they equivalent? how do you deal with such situations? Create library? Code new FileObject().new Format().new Words().new Some().new Continue someThing; ((((new FileObject()).new Format()).new Words()).new Some()).new Continue someThing;

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  • Java template classes using generator or similar?

    - by Hugh Perkins
    Is there some library or generator that I can use to generate multiple templated java classes from a single template? Obviously Java does have a generics implementation itself, but since it uses type-erasure, there are lots of situations where it is less than adequate. For example, if I want to make a self-growing array like this: class EasyArray { T[] backingarray; } (where T is a primitive type), then this isn't possible. This is true for anything which needs an array, for example high-performance templated matrix and vector classes. It should probably be possible to write a code generator which takes a templated class and generates multiple instantiations, for different types, eg for 'double' and 'float' and 'int' and 'String'. Is there something that already exists that does this? Edit: note that using an array of Object is not what I'm looking for, since it's no longer an array of primitives. An array of primitives is very fast, and uses only as much space a sizeof(primitive) * length-of-array. An array of object is an array of pointers/references, that points to Double objects, or similar, which could be scattered all over the place in memory, require garbage collection, allocation, and imply a double-indirection for access. Edit2: good god, voted down for asking for something that probably doesn't currently exist, but is technically possible and feasible? Does that mean that people looking for ways to improve things have already left the java community? Edit3: Here is code to show the difference in performance between primitive and boxed arrays: int N = 10*1000*1000; double[]primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } Object[] objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } tic(); primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } toc(); tic(); objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } toc(); Results: double[] array: 148 ms Double[] array: 4614 ms Not even close!

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  • why does my C# client that uses Library A need to have a using statement for Library B (which A uses

    - by Greg
    Hi, I have: Main Program Class - uses Library A Library A - has partial classes which mix in methods from Library B Library B - mix in methods & interfaces So in Library B when I include a partial Node class which implements INode (defined in Library B) I suddenly get an error in my main class where it uses Node from Library A. The error tells me in the Main Class I have to have a using statement to Library B. Any ideas?

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  • Are classes in Python in different files?

    - by Asaf
    Much like Java (or php), I'm use to seperating the classes to files. Is it the same deal in Python? plus, how should I name the file? Lowercase like classname.py or the same like ClassName.py? Do I need to do something special if I want to create an object from this class or does the fact that it's in the same "project" (netbeans) makes it ok to create an object from it?

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  • Where to define exception classes, inside classes or on a higher level?

    - by rve
    Should exception classes be part of the class which may throw them or should they exist on a higher level? For example : class Test { public: class FooException: public ExceptionBase { }; void functionThrowingFooException(); }; or class FooException: public ExceptionBase { }; class Test { public: void functionThrowingFooException(); }; (functionThrowingFooException() is the only function to ever throw a FooException)

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  • How to give properties to c++ classes (interfaces)

    - by caas
    Hello, I have built several classes (A, B, C...) which perform operations on the same BaseClass. Example: struct BaseClass { int method1(); int method2(); int method3(); } struct A { int methodA(BaseClass& bc) { return bc.method1(); } } struct B { int methodB(BaseClass& bc) { return bc.method2()+bc.method1(); } } struct C { int methodC(BaseClass& bc) { return bc.method3()+bc.method2(); } } But as you can see, each class A, B, C... only uses a subset of the available methods of the BaseClass and I'd like to split the BaseClass into several chunks such that it is clear what it used and what is not. For example a solution could be to use multiple inheritance: // A uses only method1() struct InterfaceA { virtual int method1() = 0; } struct A { int methodA(InterfaceA&); } // B uses method1() and method2() struct InterfaceB { virtual int method1() = 0; virtual int method2() = 0; } struct B { int methodB(InterfaceB&); } // C uses method2() and method3() struct InterfaceC { virtual int method2() = 0; virtual int method3() = 0; } struct C { int methodC(InterfaceC&); } The problem is that each time I add a new type of operation, I need to change the implementation of BaseClass. For example: // D uses method1() and method3() struct InterfaceD { virtual int method1() = 0; virtual int method3() = 0; } struct D { int methodD(InterfaceD&); } struct BaseClass : public A, B, C // here I need to add class D { ... } Do you know a clean way I can do this? Thanks for your help edit: I forgot to mention that it can also be done with templates. But I don't like this solution either because the required interface does not appear explicitly in the code. You have to try to compile the code to verify that all required methods are implemented correctly. Plus, it would require to instantiate different versions of the classes (one for each BaseClass type template parameter) and this is not always possible nor desired.

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  • Internal classes with ADO.NET Entity Framework

    - by Regent
    I'm using Entity Framework for creation of my Data Access Layer and I want for all of my classes to be internal. I know it is possible to manually assign it manually in the designer for each class. But looks like it also requires to set internal modifier for each single property in every class! I have about 30+ entities and it will be a huge work to do. Do you know any ideas how to set a 'default access' for the entire model?

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  • How initialize array of classes? (C++)

    - by Kra
    Hello, I have this class constructor: Pairs (int Pos, char *Pre, char *Post, bool Attach = true); How can I initialize array of Pairs classes? I tried: Pairs Holder[3] = { {Input.find("as"), "Pre", "Post"}, {Input.find("as"), "Pre", "Post"}, {Input.find("as"), "Pre", "Post"} }; Apparently it's not working, I also tried to use () brackets instead of {} but compiler keeps moaning all the time. Sorry if it is lame question, I googled quite hard but wasn't able to find answer :/ Thanks.

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  • Overriding Built-in Classes (Python)

    - by Yipeng
    How can I view and override the full definition for built in classes? I have seen the library docs but am looking for something more. For e.g. is it possible to override the Array Class such that the base index starts from 1 instead of 0, or to override .sort() of list to a sorting algorithm of my own liking?

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  • private classes inside namespaces

    - by blacklion
    Is there a way to restrict access to a class from outside a namespace? What I want is to have a class that is only accessible to other classes inside the same namespace without having to put the namespace in it's own assembly. Is there a reason this is not possible in C#?

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  • PHP-OOP extending two classes?

    - by user1292810
    I am very beginner to OOP and now I am trying to write some PHP class to connect with FTP server. class ftpConnect { private $server; private $user; private $password; private $connection_id; private $connection_correct = false; public function __construct($server, $user = "anonymous", $password = "[email protected]") { $this->server = $server; $this->user = $user; $this->password = $password; $this->connection_id = ftp_connect($this->server); $this->connection_correct = ftp_login($this->connection_id, $this->user, $this->password); if ( (!$this->connection_id) || (!$this->connection_correct) ){ echo "Error! Couldn't connect to $this->server"; var_dump($this->connection_id); var_dump($this->connection_correct); return false; } else { echo "Successfully connected to $this->server, user: $this->user"; $this->connection_correct = true; return true; } } } I reckon that body of the class is insignificant at the moment. Main issue is that I have some problems with understanding OOP idea. I wanted to add sending emails every time, when the code is run. I have downloaded PHPMailer Class and extended my class with it: class ftpConnect extends PHPMailer {...} I have added some variables and methods and everything works as expected to that point. I thought: why not to add storing everything in database. Everytime user runs above code, proper information should be stored in database. I could edit my ftpConnect class and add database connecting to the constructor, and some other methods to updating tables. But database connecting and all that stuff could be used by other classes in the future, so it definitely should be implemented in seperate class. But my "main" ftpConnect class already extends one class and could not extend not a single one more. I have no idea how can I resolve this problem. Maybe my ftpConnect class is to complex and I should somehow divide it into couple smaller classes? Any help is much appreciated.

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  • CSS single property classes

    - by user1490379
    As more presentational html properties get deprecated the natural response for me was to make single property CSS classes such as .text-align-left{text-align:left}. My question is, is this preferred versus inline styles? Stackoverflow actually uses quite a bit of inline styles. PS: I know this isn't really a coding question and it is likely to incite debate but stackoverflow is the largest stack exchange for code and this question does have some use for future individuals.

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  • One-to-One relation classes

    - by SeyZ
    I want to have a class named ProjectDirectory and a class named MetaDirectory. Each project has a MetaDirectory which contains some meta data. Is it the good way to write the classes like this: class ProjectDirectory(object): def __init__(self, directory=None): self.directory = directory self.meta_directory = MetaDirectory(self) def __repr__(self): return self.directory class MetaDirectory(object): def __init__(self, project_directory=None): self.project_directory = project_directory self.directory = "%s/.meta/" % project_directory ProjectDirectory has a reference to MetaDirectory and MetaDirectory has a reference to ProjectDirectory. Is there an other solution or this solution is good ?

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  • java.rmi.UnmarshalException: unable to pull client classes by server

    - by andrews
    Hi, I have an RMI client/server set-up on two machines that works fine in a simple situation when the server doesn't require a client-side defned class. However, when I need to use a class defined on the client side I am unable to have the server unmarshall those classes. I suspect this is an issue with my java.rmi.server.codebase property that I pass in as argument to the client app. I followed Sun's RMI Tutorial trail and I think I have followed the steps exactly except that I don't specify a classpath argument when executing client and server because they execute in the directory right above the root package directory (however I tried that too with no effect). The exceptions I get when attempting to execute the different client-side combinations described in detail below are all the same: RmiServer exception: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: java.lang.ClassNotFoundException: test.MyTask at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:353) at sun.rmi.transport.Transport$1.run(Transport.java:177) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:173) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:142) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132) at $Proxy0.execute(Unknown Source) at test.myClient.main(myClient.java:32) The details are: My client/server rmi is set up over a home network behind a router. The router is assigned to a static ip address I will call myhostname. Appropriate port-mapping is set-up in the router that points to the right machines. role, machine, os, ip-address: server, venice, linux ubuntu 9.10, 10.0.1.2 client, naples, mac os x leopard, 10.0.1.4 I startup the server side as follows inside /home/andrews/workspace/epsilon/bin: 1 starting registry on the default port 1099: venice% rmiregistry & 2 starting web-server on port 2001 pointing to code base for common interfaces: venice% java webserver/ClassFileServer 2001 /home/andrew/workspace/epsilon/bin 3 starting server app (main class in test/myServer) which registers the server object: venice% java -Djava.rmi.server.codebase="http://myhostname:2001/" -Djava.security.policy=server.policy -Djava.rmi.server.hostname=myhostname test/myServer & Now the client side inside /Users/andrews/Development/Java/workspace/epsilon/bin: 1 start a local web server that can server client-side classes to the server (not sure if this is needed, but I added I tried it, and still no success; I have added port-mapping to the router for 2001 to venice, for 2002 to naples) naples$ java webserver/ClassFileServer 2002 /Users/andrews/Development/Java/workspace/epsilon/bin/ Trying to run the client (note: I don't specify the -cp argument because client executes right above the root package directory): 1 try #1 using an http hostname naples$ java -Djava.rmi.server.codebase=http://10.0.1.4:2002/ -Djava.security.policy=client.policy test.myClient myhostname Note 1: the myhostname argument at the end is passed-in to the client so that it resolves to server's rmi hostname. Note 2: I tried using localhost:2002 instead of 10.0.1.4:2002 too. Note 3: I tried using myhostname:2002 since myhostname is assigned to the router and I have proper port-mapping set-up, this address should resolve to naples and not venice 2 try #2: naples$ java -Djava.rmi.server.codebase=file:/Users/andrews/Development/Java/workspace/epsilon/bin/ -Djava.security.policy=client.policy test.myClient myhostname Note 1: the code base url format is correct, I created a small program to convert current file directory path into a url and used that. using file:///Users... has same effect. Other notes: 1 my server and client policy files correctly specify the path, as I've tested this setup with good and bad paths, and getting a security exception for bad path 2 this setup works if I don't use client-side defined objects, the client connects correctly to the server and the server executes. 3 when I place the client-side class on the server in the server's classpath, all executes fine. All help is appreciated.

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  • xmlns='' was not expected when deserializing nested classes

    - by Mavrik
    I have a problem when attempting to serialize class on a server, send it to the client and deserialize is on the destination. On the server I have the following two classes: [XmlRoot("StatusUpdate")] public class GameStatusUpdate { public GameStatusUpdate() {} public GameStatusUpdate(Player[] players, Command command) { this.Players = players; this.Update = command; } [XmlArray("Players")] public Player[] Players { get; set; } [XmlElement("Command")] public Command Update { get; set; } } and [XmlRoot("Player")] public class Player { public Player() {} public Player(PlayerColors color) { Color = color; ... } [XmlAttribute("Color")] public PlayerColors Color { get; set; } [XmlAttribute("X")] public int X { get; set; } [XmlAttribute("Y")] public int Y { get; set; } } (The missing types are all enums). This generates the following XML on serialization: <?xml version="1.0" encoding="utf-16"?> <StatusUpdate> <Players> <Player Color="Cyan" X="67" Y="32" /> </Players> <Command>StartGame</Command> </StatusUpdate> On the client side, I'm attempting to deserialize that into following classes: [XmlRoot("StatusUpdate")] public class StatusUpdate { public StatusUpdate() { } [XmlArray("Players")] [XmlArrayItem("Player")] public PlayerInfo[] Players { get; set; } [XmlElement("Command")] public Command Update { get; set; } } and [XmlRoot("Player")] public class PlayerInfo { public PlayerInfo() { } [XmlAttribute("X")] public int X { get; set; } [XmlAttribute("Y")] public int Y { get; set; } [XmlAttribute("Color")] public PlayerColor Color { get; set; } } However, the deserializer throws an exception: There is an error in XML document (2, 2). <StatusUpdate xmlns=''> was not expected. What am I missing or doing wrong? EDIT: On request I'm also adding code used to serialize and deserialize: Server: public static byte[] SerializeObject(Object obj) { XmlSerializer xmlSerializer = new XmlSerializer(obj.GetType()); StringWriter writer = new StringWriter(); // Clear pre-defined namespaces XmlSerializerNamespaces xsn = new XmlSerializerNamespaces(); xsn.Add("", ""); xmlSerializer.Serialize(writer, obj, xsn); writer.Flush(); // Send as little-endian UTF-16 string because the Serializer denotes XML as // utf-18 which cannot be easly changed UnicodeEncoding encoder = new UnicodeEncoding(false, false); return encoder.GetBytes(writer.ToString()); } Client: public static object DeserializeXml(string xmlData, Type type) { XmlSerializer xmlSerializer = new XmlSerializer(type); StringReader reader = new StringReader(xmlData); object obj = xmlSerializer.Deserialize(reader); return obj; } Deserialization is invoked with StatusUpdate update = (StatusUpdate) Util.DeserializeXml(xmlData, typeof (StatusUpdate));

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  • Are injectable classes allowed to have constructor parameters in DI?

    - by Songo
    Given the following code: class ClientClass{ public function print(){ //some code to calculate $inputString $parser= new Parser($inputString); $result= $parser->parse(); } } class Parser{ private $inputString; public __construct($inputString){ $this->inputString=$inputString; } public function parse(){ //some code } } Now the ClientClass has dependency on class Parser. However, if I wanted to use Dependency Injection for unit testing it would cause a problem because now I can't send the input string to the parser constructor like before as its calculated inside ClientCalss itself: class ClientClass{ private $parser; public __construct(Parser $parser){ $this->parser=$parser; } public function print(){ //some code to calculate $inputString $result= $this->parser->parse(); //--> will throw an exception since no string was provided } } The only solution I found was to modify all my classes that took parameters in their constructors to utilize Setters instead (example: setInputString()). However, I think there might be a better solution than this because sometimes modifying existing classes can cause much harm than benefit. So, Are injectable classes not allowed to have input parameters? If a class must take input parameters in its constructor, what would be the way to inject it properly? UPDATE Just for clarification, the problem happens when in my production code I decide to do this: $clientClass= new ClientClass(new Parser($inputString));//--->I have no way to predict $inputString as it is calculated inside `ClientClass` itself. UPDATE 2 Again for clarification, I'm trying to find a general solution to the problem not for this example code only because some of my classes have 2, 3 or 4 parameters in their constructors not only one.

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