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  • Why does the Java compiler complain about a local variable not having been initialized here?

    - by pele
    int a = 1, b; if(a > 0) b = 1; if(a <= 0) b = 2; System.out.println(b); If I run this, I receive: Exception in thread "main" java.lang.Error: Unresolved compilation problem: The local variable b may not have been initialized at Broom.main(Broom.java:9) I know that the local variables are not initialized and is your duty to do this, but in this case, the first if doesn't initialize the variable?

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  • Object Deletion: use parent or not

    - by metdos
    Which one do you prefer to delete objects? Especially in QT, but other practices are also welcome. These two alternatives seem same to me, are they? 1.Bound to another class, and destroy when it is destroyed. SomeClass::SomeClass{ socket_ = new QTcpSocket(this); } or 2.Destroy in the destructor of class SomeClass::SomeClass{ socket_ = new QTcpSocket(); } SomeClass::~SomeClass{ delete socket_; }

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  • Is it good practice to initialize array in C/C++?

    - by sand
    I recently encountered a case where I need to compare two files (golden and expected) for verification of test results and even though the data written to both the files were same, the files does not match. On further investigation, I found that there is a structure which contains some integers and a char array of 64 bytes, and not all the bytes of char array were getting used in most of the cases and unused fields from the array contain random data and that was causing the mismatch. This brought me ask the question whether it is good practice to initialize the array in C/C++ as well, as it is done in Java?

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  • Where to add an observer to the NotificationCenter in a UITableViewController

    - by Saifis
    I want to send a notification from a UITableViewController-A to UITableViewController-B. I was adding the observer in the initwithCoder of the UITableViewController that is supposed to catch the notifications. The classes are correlated as folows RootViewController ===NavigationController-A =====UITableViewController-A ===NavigationController-B =====UITableViewController-B I need to add the observer before the views are actually loaded because notifications may be sent before the view is called. However I have been told that initializing in the initWithCoder method in a UIViewController is not advisable, and was told to add the observer in the AppDelegate. Are there any other suggestions for doing this?

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  • c++ Initializing a struct with an array as a member

    - by Drew Shafer
    I've got the following reduced testcase: typedef struct TestStruct { int length; int values[]; }; TestStruct t = {3, {0, 1, 2}}; This works with Visual C++, but doesn't compile with g++ under linux. Can anyone help me make this specific kind of initializer portable? Additional details: the actual structure I'm working with has several other int values, and the array can range in length from a single entry to over 1800 entries. Any help much appreciated. Thanks!

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  • Undefined / Uninitialized default values in a class

    - by Jir
    Let's suppose you have this class: class A { public: A () {} A (double val) : m_val(val) {} ~A () {} private: double m_val; }; Once I create an instance of A, how can I check if m_val has been initialized/defined? Put it in other words, is there a way to know if m_val has been initialized/defined or not? Something along the lines of the defined operator in Python, I suppose. (But correct me if I'm wrong.) I thought of modifying the class and the c-tors the following way: class A { public: A () : defined(false) {} A (double val) : m_val(val), defined(true) {} ~A () {} private: double m_val; bool defined; }; How do you rate this solution? Any suggestion? TIA, Chris

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  • c++/boost: use tuple ctors when subclassing

    - by bbb
    Hi there, is there some way to use a boost tuple's ctors as an addition to the subclass methods (and ctors) like here? // typedef boost::tuple<int, SomeId, SomeStatus> Conn; // Conn(1); // works and initializes using default ctors of Some* struct Conn : boost::tuple<int, AsynchId, AccDevRetStatus> {}; Conn(1); // "no matching function call" (but i want it so much) T.H.X.

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  • Iterating through boost ptr_vector

    - by Ockonal
    Hello, I have a ptr_vector list of my own objects. Something like this: boost::ptr_vector<SomeClass> *list; list.push_back(new SomeClass()>; ... BOOST_FOREACH(SomeClass *tempObj, list) // [x] { tempObj->... } >‘boost::ptr_vector<SomeClass>*’ is not a class, struct, or union type

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  • How to default-initialize local variables of built-in types in C++?

    - by sharptooth
    How do I default-initialize a local variable of primitive type in C++? For example if a have a typedef: typedef unsigned char boolean;//that's Microsoft RPC runtime typedef I'd like to change the following line: boolean variable = 0; //initialize to some value to ensure reproduceable behavior retrieveValue( &variable ); // do actual job into something that would automagically default-initialize the variable - I don't need to assign a specific value to it, but instead I only need it to be intialized to the same value each time the program runs - the same stuff as with a constructor initializer list where I can have: struct Struct { int Value; Struct() : Value() {} }; and the Struct::Value will be default-initialized to the same value every time an instance is cinstructed, but I never write the actual value in the code. How can I get the same behavior for local variables?

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  • jQuery global variable problem

    - by Emanuel
    var id = $(this).children().html(); // id is 5 $.ajax({ url: 'ajax.php?id=' + id, success: function(data) { id = data; // id is 1 } }); if(id == 1){ // id is again 5 ... } Why in the following example I can't reinitialize the id variable? What is wrong? Thanks.

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  • Statically initialize anonymous union in C++

    - by wpfwannabe
    I am trying to statically initialize the following structure in Visual Studio 2010: struct Data { int x; union { char ch; const Data* data; }; }; The following is fails with error C2440: 'initializing' : cannot convert from 'Data *' to 'char'. static Data d1; static Data d = {1, &d1}; I have found references to some ways this can be initialized properly but none of them work in VS2010. Any ideas?

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  • How/When/Where to Extend Gem Classes (via class_eval and Modules) in Rails 3?

    - by viatropos
    What is the recommended way to extend class behavior, via class_eval and modules (not by inheritance) if I want to extend a class buried in a Gem from a Rails 3 app? An example is this: I want to add the ability to create permalinks for tags and categories (through the ActsAsTaggableOn and ActsAsCategory gems). They have defined Tag and Category models. I want to basically do this: Category.class_eval do has_friendly_id :title end Tag.class_eval do has_friendly_id :title end Even if there are other ways of adding this functionality that might be specific to the gem, what is the recommended way to add behavior to classes in a Rails 3 application like this? I have a few other gems I've created that I want to do this to, such as a Configuration model and an Asset model. I would like to be able to add create an app/models/configuration.rb model class to my app, and it would act as if I just did class_eval. Anyways, how is this supposed to work? I can't find anything that covers this from any of the current Rails 3 blogs/docs/gists.

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  • How to create lines with Athens?

    - by Kilon
    I have no clue how to create lines with Athens. I took a look at Cairo docs but I cant see how Athens is related to Cairo. http://zetcode.com/gfx/cairo/basicdrawing/ In the above link I cant find any equivalent for cairo_set_line_width(cr, 1); I tried to look inside Athens but is nowhere to be found. Overall I find the Athens architecture quite confusing though Cairo looks simple. Any idea how to makes this work ?

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  • Best way to initialise / clear a string variable cocoa

    - by Spider-Paddy
    I have a routine that parses text via a loop. At the end of each record I need to clear my string variables but I read that someString = @"" actually just points to a new string & causes a memory leak. What is the best way to handle this? Should I rather use mutable string vars and use setString:@"" between iterations?

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  • C# Automatic Properties - Still null after +=?

    - by Sam Schutte
    This seems like a bug to me... I accept that automatic properties, defined as such: public decimal? Total { get; set; } Will be null when they are first accessed. They haven't been initialized, so of course they are null. But, even after setting their value through +=, this decimal? still remains null. So after: Total += 8; Total is still null. How can this be correct? I understand that it's doing a (null + 8), but seems strange that it doesn't pick up that it means it should just be set to 8... Addendums: I made the "null + 8" point in my question - but notice that it works with strings. So, it does null + "hello" just fine, and returns "hello". Therefore, behind the scenes, it is initializing the string to a string object with the value of "hello". The behavior should be the same for the other types, IMO. It might be because a string can accept a null as a value, but still, a null string is not an initialized object, correct? Perhaps it's just because a string isn't a nullable...

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  • How can i initialise a server on startup?

    - by djerry
    Hey all, I need to make some connections on startup of a server. I'm using the wcf technology for this client-server application. The problem is that the constructor of the server isn't called at any time, so for the moment, i initialize the connections when the first client makes a connection. But this generates problems in a further part. This is my server setup: private static ServiceHost _svc; static void Main(string[] args) { NetTcpBinding binding = new NetTcpBinding(SecurityMode.Message); Uri address = new Uri("net.tcp://localhost:8000"); _svc = new ServiceHost(typeof(MonitoringSystemService), address); publishMetaData(_svc, "http://localhost:8001"); _svc.AddServiceEndpoint(typeof(IMonitoringSystemService), binding, "Monitoring Server"); _svc.Open(); Console.WriteLine("Listener service gestart op net.tcp://localhost:8000/Monitoring"); Console.ReadLine(); } private static void publishMetaData(ServiceHost svc, string sEndpointAddress) { ServiceMetadataBehavior smb = svc.Description.Behaviors.Find<ServiceMetadataBehavior>(); if (smb != null) { smb.HttpGetEnabled = true; smb.HttpGetUrl = new Uri(sEndpointAddress); } else { smb = new ServiceMetadataBehavior(); smb.HttpGetEnabled = true; smb.HttpGetUrl = new Uri(sEndpointAddress); svc.Description.Behaviors.Add(smb); } } How can i start the server without waiting for a client to logon so i can initialize it. Thanks in advance.

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  • Transform shape built of contour splines to simple polygons

    - by Cheery
    I've dumped glyphs from truetype file so I can play with them. They have shape contours that consist from quadratic bezier curves and lines. I want to output triangles for such shapes so I can visualize them for the user. Traditionally I might use libfreetype or scan-rasterise this kind of contours. But I want to produce extruded 3D meshes from the fonts and make other distortions with them. So, how to polygonise shapes consisting from quadratic bezier curves and lines? There's many contours that form the shape together. Some contours are additive and others are subtractive. The contours are never open. They form a loop. (Actually, I get only contour vertices from ttf glyphs, those vertices define whether they are part of the curve or not. Even though it is easy to decompose these into bezier curves and lines, knowing the data is represented this way may be helpful for polygonizing the contours to triangles)

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  • intialization with a nibFIle failed

    - by zp26
    Hi, I have a problem. I try to initialize a variabile in a classViewController created inside a xib file. I try with the code below but when i append a object to array, these array isn't initialized. Can you help me? thanks and sorry for my english. #import <UIKit/UIKit.h> @interface AccelerometroViewController : UIViewController <UIAccelerometerDelegate, UITextFieldDelegate, UIAlertViewDelegate>{ //..... NSMutableArray *arrayPosizioni; NSMutableArray *arrayPosizioniCorrenti; NSString *nomePosizioneCorrente; } -(IBAction)salvaPosizione; //... @property (nonatomic, assign) NSMutableArray *arrayPosizioni; @property (nonatomic, assign) NSMutableArray *arrayPosizioniCorrenti; @property (nonatomic, assign) NSString *nomePosizioneCorrente; @end #import "AccelerometroViewController.h" #import "Position.h" @implementation AccelerometroViewController float actualX; float actualY; float actualZ; @synthesize arrayPosition; @synthesize arrayCurrentPosition; @synthesize nameCurrentPosition; -(id)init { self = [super init]; if (self != nil) { arrayPosition = [[NSMutableArray alloc]init]; arrayCurrentPosition = [[NSMutableArray alloc]init]; nameCurrentPosition = [NSString stringWithFormat:@"noPosition"]; actualX = 0; actualY = 0; actualZ = 0; } return self; } -(void)updateTextView:(NSString*)nomePosizione { NSString *string = [NSString stringWithFormat:@"%@", nameCurrentPosition]; textEvent.text = [textEvent.text stringByAppendingString:@"\n"]; textEvent.text = [textEvent.text stringByAppendingString:string]; } -(IBAction)savePosition{ Posizione *newPosition; newPosition = [[Position alloc]init]; if([newPosition setValue:(NSString*)fieldNomePosizione.text:(float)actualX:(float)actualY:(float)actualZ]){ //setValue is a method of Position. I'm sure that this method is correct UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Salvataggio Posizione" message:@"Posizione salvata con successo" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; [alert show]; [alert release]; [arrayPosition addObject:newPosition]; } else{ UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Salvataggio osizione" message:@"Errore nel salvataggio" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; [alert show]; [alert release]; } } - (void) initialise { arrayPosition = [[NSMutableArray alloc] init]; arrayCurrentPosition = [[NSMutableArray alloc] init]; nameCurrentPosition = @"noPosition"; actualX = 0; actualY = 0; actualZ = 0; } - (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle { if (self = [super initWithNibName:nibName bundle:bundle]) { [self initialise]; } }

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  • Python - Create a list with initial capacity

    - by Claudiu
    Code like this often happens: l = [] while foo: #baz l.append(bar) #qux This is really slow if you're about to append thousands of elements to your list, as the list will have to constantly be re-initialized to grow. (I understand that lists aren't just wrappers around some array-type-thing, but something more complicated. I think this still applies, though; let me know if not). In Java, you can create an ArrayList with an initial capacity. If you have some idea how big your list will be, this will be a lot more efficient. I understand that code like this can often be re-factored into a list comprehension. If the for/while loop is very complicated, though, this is unfeasible. Is there any equivalent for us python programmers?

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  • Reference variable to an object instantiated/initialized in another class in Java

    - by Alex
    The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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  • Java: how to initialize String[]?

    - by Heoa
    Error % javac StringTest.java StringTest.java:4: variable errorSoon might not have been initialized errorSoon[0] = "Error, why?"; Code public class StringTest { public static void main(String[] args) { String[] errorSoon; errorSoon[0] = "Error, why?"; } }

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