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  • Register all GUI components as Observers or pass current object to next object as a constructor argu

    - by Jack
    First, I'd like to say that I think this is a common issue and there may be a simple or common solution that I am unaware of. Many have probably encountered a similar problem. Thanks for reading. I am creating a GUI where each component needs to communicate (or at least be updated) by multiple other components. Currently, I'm using a Singleton class to accomplish this goal. Each GUI component gets the instance of the singleton and registers itself. When updates need to be made, the singleton can call public methods in the registered class. I think this is similar to an Observer pattern, but the singleton has more control. Currently, the program is set up something like this: class c1 { CommClass cc; c1() { cc = CommClass.getCommClass(); cc.registerC1( this ); C2 c2 = new c2(); } } class c2 { CommClass cc; c2() { cc = CommClass.getCommClass(); cc.registerC2( this ); C3 c3 = new c3(); } } class c3 { CommClass cc; c3() { cc = CommClass.getCommClass(); cc.registerC3( this ); C4 c4 = new c4(); } } etc. Unfortunately, the singleton class keeps growing larger as more communication is required between the components. I was wondering if it's a good idea to instead of using this singleton, pass the higher order GUI components as arguments in the constructors of each GUI component: class c1 { c1() { C2 c2 = new c2( this ); } } class c2 { C1 c1; c2( C1 c1 ) { this.c1 = c1 C3 c3 = new c3( c1, this ); } } class c3 { C1 c1; C2 c2; c3( C1 c1, C2 c2 ) { this.c1 = c1; this.c2 = c2; C4 c4 = new c4( c1, c2, this ); } } etc. The second version relies less on the CommClass, but it's still very messy as the private member variables increase in number and the constructors grow in length. Each class contains GUI components that need to communicate through CommClass, but I can't think of a good way to do it. If this seems strange or horribly inefficient, please describe some method of communication between classes that will continue to work as the project grows. Also, if this doesn't make any sense to anyone, I'll try to give actual code snippets in the future and think of a better way to ask the question. Thanks.

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  • How do app servers inject into private fields?

    - by cibercitizen1
    I saw this question http://stackoverflow.com/questions/2021716/inject-into-private-package-or-public-field-or-provide-a-setter about how to manually inject into annotated private fields (The way is adding setters or through a constructor) But, the point is how do an application server (like glassfish, axis2, jboss, ...) is able to inject into a final private field (without adding setters or constructors to the user class)? Quoting the cited question: public SomeClass { @Inject private SomeResource resource; } Do they use a customized JVM (not the standard one) that allows to access private fields? Thanks

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  • Refcounted pointers on iPhone

    - by anon
    1) Refcounted pointers need stack variables to have constructors / destructors called at predictable places. 2) Objective-C, afaik, does not support the above. 3) The cocoa libraries are bound in Objective-C, not C++. Thus, my question: is there a easy way to use the Cocoa libraries, yet still have most of my app in C++ (and thus use my refcounted pointers)? Thanks! (iPhone in the title since this is mainly targeted at the iPhone)

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  • std::string x(x);

    - by FredOverflow
    std::string x(x); This crashes very badly on my compiler. Does this mean I should test for this != &that in my own copy constructors, or can I assume that no client will ever be so stupid?

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  • What is the best scala-like persistence framework available right now?

    - by egervari
    What is the best scala-like persistence framework available right now? Hibernate works, but it's not very scala-like. It insists on using annotations, no-arg constructors, doesn't work with anonymous class instances, doesn't work with scala collections, has an outdated string-based query model, etc. I'm looking for something that really fits Scala. Does it exist? Or do I have to make it?

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  • how to access class and its functions from another class

    - by vbNewbie
    This is my first major application using multiple classes. It is written in vb and I know about creating objects of the class and using that instance to call functions of the class. But how do I create an object with constructors to allow another program written in C# to access my classes and functions and accept things from the program. Hope this makes sense.

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  • Define Default constructor Structuremap in a Generic Repository

    - by Ricky
    Hello guys, I have a generic IRepository that has 2 constructors, one have none parameters, other has the datacontext as parameter. I want to define to structuremap to aways in this case use the parameterless constructor. I want a way to create a parameterless contructor, other solutions that I have seen, they create a new Datacontext and pass it to the constructor that has parameters.

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  • Using memcpy in the STL

    - by wowus
    Why does C++'s vector class call copy constructors? Why doesn't it just memcpy the underlying data? Wouldn't that be a lot faster, and remove half of the need for move semantics? I can't imagine a use case where this would be worse, but then again, maybe it's just because I'm being quite unimaginative.

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  • Boost::Serialization Mpi Sending array of user defined types

    - by Noman Javed
    I want to send my Array class using boost Mpi template class Array { private: int size; T* data; public: // constructors + other stuff }; Here T can be any built in type or user defined type. Suppose I have a class complex struct complex { std::vector real_imag; // contain two elements }; So the question is how can I send Array using Boost::Mpi + serialization. Thanks in anticipation Regards Noman

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  • DRY Ruby Initialization with Hash Argument

    - by ktex
    I find myself using hash arguments to constructors quite a bit, especially when writing DSLs for configuration or other bits of API that the end user will be exposed to. What I end up doing is something like the following: class Example PROPERTIES = [:name, :age] PROPERTIES.each { |p| attr_reader p } def initialize(args) PROPERTIES.each do |p| self.instance_variable_set "@#{p}", args[p] if not args[p].nil? end end end Is there no more idiomatic way to achieve this? The throw-away constant and the symbol to string conversion seem particularly egregious.

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  • Good suggestions for learning OOP PHP

    - by Doug
    I've been trying to learn PHP OOP and have looked at multiple articles, but have yet to find a good resource for learning. I want to learn from the user of setters and getters, $this-, constructors, and so on...! Can anyone please suggest me something? I noticed MOST teachings leave out the explanation of $this-. I want to learn magic methods, decorators, encapsulation, etc... Feel free to suggest something that I haven't explicitly listed.

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  • Ctor not allowed return type.

    - by atch
    Having code: struct B { int* a; B(int value):a(new int(value)) { } B():a(nullptr){} B(const B&); } B::B(const B& pattern) { } I'm getting err msg: 'Error 1 error C2533: 'B::{ctor}' : constructors not allowed a return type' Any idea why? P.S. I'm using VS 2010RC

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  • setting z-index jquery ui controls?

    - by maxp
    Annoyingly, the jquery ui's set a few css properties inline, making it impossible to override them in the stylesheet. I tried to override the values with jquery, but then they get changed back as soon as the control is interacted with. Does anyone know if any of the jquery ui control's initialisers/constructors have the ability to override their z-index value or set other css properties?

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  • Use reflection to get a list of static classes

    - by Christian
    Hi, many questions are close, but none answers my problem... How do I use reflection in C# 3.5 to get all classes which are static from an assembly. I already get all Types defined, but there is no IsStatic property. Counting 0 constructors is really slow and did not work either. Any tips or a line of code? :-) Chris

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  • Writing SDK documentation, need useful beginner tutorials

    - by David Rutten
    I'm currently writing SDK documentation for one of our products, but for obvious reasons I don't want to talk about the essentials of OOP. Does anyone know any good online teaching material that explain (aimed at absolute beginners) concepts such as classes, inheritance, constructors, instances etc.? Preferably urls that are likely to survive for a couple of years to come... It's a DotNET SDK and we're including only VB and C# samples, so C++ or Delphi or Lisp material is not that useful.

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  • JNI cached jclass global reference variables being garbage collected?

    - by bubbadoughball
    I'm working in the JNI Invocation API, calling into Java from C. I have some upfront initialization to cache 30+ Java classes into global references. The results of FindClass are passed into NewGlobalRef to acquire a global reference to the class. I'm caching these class variables to reuse them later. I have 30+ global references to classes (and 30+ global methodIDs for the class constructors). In the following sample, I've removed exception handling as well as JNI invocation for the purpose of shortening the code snippet. My working code has exception checks after every JNI call and I'm running with -Xcheck:jni. Here's the snippet: jclass aClass; jclass bClass; jmethodID aCtor; jmethodID bCtor; void getGlobalRef(const char* clazz, jclass* globalClass) { jclass local = (*jenv)->FindClass(jenv,clazz); if (local) { *globalClass = (jclass) (*jenv)->NewGlobalRef(jenv,local); (*jenv)->DeleteLocalRef(jenv,local); } } methodID getMethodID(jclass clazz, const char* method, const char* sig) { return (*jenv)->GetMethodID(jenv,clazz,method,sig); } void initializeJNI() { getGlobalRef("MyProj/Testclass1", &aclass); getGlobalRef("MyProj/Testclass2", &bclass); . . aCtor = getMethodID(aclass,"<init>","()V"); bCtor = getMethodID(bclass,"<init>","(I)V"); } The initializeJNI() function sets the global references for jclasses and method IDs for constructors as well as some jfieldID's and some initialization of C data structures. After initialization, when I call into a JNI function using some of the cached jclasses and ctor jmethodIDs, I get a bad global or local reference calling reported from the -Xcheck:jni. In gdb, I break at the last line of initializeJNI(), and print all jclasses and jmethodIDs and the ones causing problems look to have been turned into garbage or garbage-collected (i.e. 0x00 or 0x06). Is it possible for global references to be gc'ed? Any suggestions?

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  • Can a constructor return a NULL value?

    - by Sanctus2099
    I know constructors don't "return" anything but for instance if I call CMyClass *object = new CMyClass() is there any way to make object to be NULL if the constructor fails? In my case I have some images that have to be loaded and if the file reading fails I'd like it to return null. Is there any way to do that? Thanks in advance.

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  • ReSharper: find derived types constructor usages points

    - by Roman
    I have some base class ControlBase and many derived classes which also have derived classes... ControlBase and derived classes have parameterless constructor. How can I easily find all derived classes constructor invocation points? ReSharper find usages on ControlBase constructor shows only usages of this base class constructor but not derived classes constructors. Thanks.

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  • constructorless initialization and Dictionaries

    - by Stacey
    Using C# 3.0, we can initialize objects without their constructors for syntactical reasons. Such as .. ClassName c = new ClassName = { Property1 = "Value" } I was wondering how this works with Dictionaries and adding the items to them. Any ideas? class Foo { public Dictionary DictionaryObject { get; set; } } Foo f = new Foo = { // ??? } Thank you for your time!!

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  • Entity Framework .. partial constructor

    - by adamjellyit
    Hi .. I intend to extend the constructors of some of the entities in my Entity Framework (4). However how do I ensure that my constructor is run after the model has run its. i.e. I want to ensure that the the object holds the data from the database before I work on it in my constructor.

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  • Loosely coupled implicit conversion

    - by ltjax
    Implicit conversion can be really useful when types are semantically equivalent. For example, imagine two libraries that implement a type identically, but in different namespaces. Or just a type that is mostly identical, except for some semantic-sugar here and there. Now you cannot pass one type into a function (in one of those libraries) that was designed to use the other, unless that function is a template. If it's not, you have to somehow convert one type into the other. This should be trivial (or otherwise the types are not so identical after-all!) but calling the conversion explicitly bloats your code with mostly meaningless function-calls. While such conversion functions might actually copy some values around, they essentially do nothing from a high-level "programmers" point-of-view. Implicit conversion constructors and operators could obviously help, but they introduce coupling, so that one of those types has to know about the other. Usually, at least when dealing with libraries, that is not the case, because the presence of one of those types makes the other one redundant. Also, you cannot always change libraries. Now I see two options on how to make implicit conversion work in user-code: The first would be to provide a proxy-type, that implements conversion-operators and conversion-constructors (and assignments) for all the involved types, and always use that. The second requires a minimal change to the libraries, but allows great flexibility: Add a conversion-constructor for each involved type that can be externally optionally enabled. For example, for a type A add a constructor: template <class T> A( const T& src, typename boost::enable_if<conversion_enabled<T,A>>::type* ignore=0 ) { *this = convert(src); } and a template template <class X, class Y> struct conversion_enabled : public boost::mpl::false_ {}; that disables the implicit conversion by default. Then to enable conversion between two types, specialize the template: template <> struct conversion_enabled<OtherA, A> : public boost::mpl::true_ {}; and implement a convert function that can be found through ADL. I would personally prefer to use the second variant, unless there are strong arguments against it. Now to the actual question(s): What's the preferred way to associate types for implicit conversion? Are my suggestions good ideas? Are there any downsides to either approach? Is allowing conversions like that dangerous? Should library implementers in-general supply the second method when it's likely that their type will be replicated in software they are most likely beeing used with (I'm thinking of 3d-rendering middle-ware here, where most of those packages implement a 3D vector).

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