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  • c++ property class structure

    - by Without me Its just Aweso
    I have a c++ project being developed in QT. The problem I'm running in to is I am wanting to have a single base class that all my property classes inherit from so that I can store them all together. Right now I have: class AbstractProperty { public: AbstractProperty(QString propertyName); virtual QString toString() const = 0; virtual QString getName() = 0; virtual void fromString(QString str) = 0; virtual int toInteger() = 0; virtual bool operator==(const AbstractProperty &rightHand) = 0; virtual bool operator!=(const AbstractProperty &rightHand) = 0; virtual bool operator<(const AbstractProperty &rightHand) = 0; virtual bool operator>(const AbstractProperty &rightHand) = 0; virtual bool operator>=(const AbstractProperty &rightHand) = 0; virtual bool operator<=(const AbstractProperty &rightHand) = 0; protected: QString name; }; then I am implementing classes such as PropertyFloat and PropertyString and providing implementation for the comparator operators based on the assumption that only strings are being compared with strings and so on. However the problem with this is there would be no compiletime error thrown if i did if(propertyfloat a < propertystring b) however my implementation of the operators for each derived class relies on them both being the same derived class. So my problem is I cant figure out how to implement a property structure so that I can have them all inherit from some base type but code like what I have above would throw a compile time error. Any ideas on how this can be done? For those familiar with QT I tried using also a implementation with QVariant however QVariant doesn't have operators < and defined in itself only in some of its derived classes so it didn't work out. What my end goal is, is to be able to generically refer to properties. I have an element class that holds a hashmap of properties with string 'name' as key and the AbstractProperty as value. I want to be able to generically operate on the properties. i.e. if I want to get the max and min values of a property given its string name I have methods that are completely generic that will pull out the associated AbstactProperty from each element and find the max/min no matter what the type is. so properties although initially declared as PropertyFloat/PropertyString they will be held generically.

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  • Should every class have its own namespace?

    - by thehouse
    Something that has been troubling me for a while: The current wisdom is that types should be kept in a namespace that only contains functions which are part of the type's non-member interface (see C++ Coding Standards Sutter and Alexandrescu or here) to prevent ADL pulling in unrelated definitions. Does this imply that all classes must have a namespace of their own? If we assume that a class may be augmented in the future by the addition of non-member functions, then it can never be safe to put two types in the same namespace as either one of them may introduce non-member functions that could interfere with the other. The reason I ask is that namespaces are becoming cumbersome for me. I'm writing a header-only library and I find myself using classes names such as project::component::class_name::class_name. Their implementations call helper functions but as these can't be in the same namespace they also have to be fully qualified!

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  • Eclipse is not importing jar dependencies between two projects in the same workspace

    - by jax
    Here is the situation. I have a java project "LicenseGenerator" in eclipse that depends on commons-codec. I have therefore added the commons-codec jar file to the build path. I have Junit tests and everything is working fine. I have made a different project in the same workspace - which happens to be an Android project - that needs to use my LicenseGenerator classes. I added LicenseGenerator to the "projects" tab in the build path - the classes were recognized and I was able to use them. Everything compiled and ran. However, when the part of the LicenseGenerator that used the commons-codec was called from my Android project I got the following error. Could not find method org.apache.commons.codec.binary.Base64.encodeBase64URLSafeString, referenced from method This basically tells me that the commons-codec was not packaged which the Android project, so I added the commons-codec to the android project as well but the same error appears. how do I fix this?

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  • Eclipse is not importing jar dependencies between two projects in the same workspace

    - by jax
    Here is the situation. I have a java project "LicenseGenerator" in eclipse that depends on commons-codec. I have therefore added the commons-codec jar file to the build path. I have Junit tests and everything is working fine. I have made a different project in the same workspace - which happens to be an Android project - that needs to use my LicenseGenerator classes. I added LicenseGenerator to the "projects" tab in the build path - the classes were recognized and I was able to use them. Everything compiled and ran. However, when the part of the LicenseGenerator that used the commons-codec was called from my Android project I got the following error. Could not find method org.apache.commons.codec.binary.Base64.encodeBase64URLSafeString, referenced from method This basically tells me that the commons-codec was not packaged which the Android project, so I added the commons-codec to the android project as well but the same error appears. how do I fix this?

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  • Is it possible to specify a return type of "Derivative(of T)" for a MustOverride sub in VB.NET?

    - by Casey
    VB.NET 2008 .NET 3.5 I have two base classes that are MustInherit (partial). Let's call one class OrderBase and the other OrderItemBase. A specific type of order and order item would inherit from these classes. Let's call these WebOrder (inherits from OrderBase) and WebOrderItem (inherits from OrderItemBase). Now, in the grand scheme of things WebOrder is a composite class containing a WebOrderItem, like so: Public Class WebOrder Inherits OrderBase Public Property OrderItem() as WebOrderItem End Property End Class Public Class WebOrderItem Inherits OrderItemBase End Class In order to make sure any class that derives from OrderBase has the OrderItem property, I would like to do something like this in the OrderBase class: Public MustInherit Class OrderBase Public MustOverride Property OrderItem() as Derivative(Of OrderItemBase) End Class In other words, I want the derived class to be forced to contain a property that returns a derivative of OrderItemBase. Is this possible, or should I be using an entirely different approach?

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  • How to use SQLiteOpenHelper without or less restrictive use of Context?

    - by Pentium10
    If you extend SQLiteOpenHelper, for the Constructor you have to use a Context. I am wondering if there is a way to leave this out, and be able to work with database tables without a Context. Or at least be least restrictive, I mean a way of project/class structure that will make history the several context passings I have to do now. As it is my application has several level of classes, chained in each other, and there are a few that connects to the database, but have no whatsoever influence on the interface, so they don't actually need the Context. Are you creating your classes in the way that you pass each time a Context to them? If not, how you do, how you reuse a Context in a short class?

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  • C++ Types Impossible to Name

    - by Kirakun
    While reading Wikipedia's page on decltype, I was curious about the statement, Its [decltype's] primary intended use is in generic programming, where it is often difficult, or even impossible, to name types that depend on template parameters. While I can understand the difficulty part of that statement, what is an example where there is a need to name a type that cannot be named under C++03? EDIT: My point is that since everything in C++ has a declaration of types. Why would there ever be a case where it is impossible to name a type? Furthermore, aren't trait classes designed to yield type informations? Could trait classes be an alternative to decltype?

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  • How can a class's memory-allocated address be determined from within the contructor?

    - by Jim Fell
    Is it possible to get the memory-allocated address of a newly instantiated class from within that class's constructor during execution of said constructor? I am developing a linked list wherein multiple classes have multiple pointers to like classes. Each time a new class instantiates, it needs to check its parent's list to make sure it is included. If I try to do something like this: MyClass() // contructor { extern MyClass * pParent; for ( int i = 0; i < max; i++ ) { pParent->rels[i] == &MyClass; // error } } I get this error: error C2275: 'namespace::MyClass' : illegal use of this type as an expression Any thoughts or suggestions would be appreciated. Thanks.

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  • Files mapping architecture

    - by user326198
    I need to know How I can achieve this goal by classes : we have two different applications in the company (App1 , App2) Appl can export xml with know items ( ID , Name) we need app2 to import this data but App2 display different items (CarID, CarName) and this items defined like this with the mapping info <CarID> <Mapping name="ID"/> </CarID> <CarNAme> <Mapping name="Name"/> </CarNAme>" How I can achieve this as classes or ARCHITECTURE , i will develop this with c# I need one interface because we may support different type of files not just xml

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  • Intellij UML diagram does not show one to many relationships

    - by Calm Storm
    I am trying to follow http://www.jetbrains.com/idea/features/uml_class_diagram.html I have a few classes so when I do Ctrl + Alt + U I only see all classes and just Extends relationships. Please note that I have set the "Diagrams" options in my settings to show one to many etc. I do not see One to One, One to Many relationships at all ? I have used JPA OneToOne Annotations and they dont turn up at all? Pressing Ctrl Shift F12 does not do anything? Can someone please explain?

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  • Info on Seam's EntityQuery?

    - by Shadowman
    I've been working with Seam and JPA/Hibernate for quite some time, but have just started looking at making use of the EntityHome and EntityQuery classes more. EntityHome seems relatively straightforward in terms of what it is and how I can leverage it. But, EntityQuery is a bit less clear. I understand the ability to grab, for example, a list containing all of a given entity. However, I've also seen some examples using a RESTRICTIONS array. How exactly is this used? Are the OR conditions or AND conditions? Can anyone give me some more detailed information as to how EntityQuery is intended to be used? I've checked the few books I have on Seam and JPA, but none of them really reference the EntityQuery classes. It seems like I very useful mechanism, and I'd like to get some more use out of them if I can. Thanks!

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  • Select all items of union but not the last one!

    - by 100r
    I have few texboxes, dropdown lists, etc.. They have their css classes. I want to select all elements of specific class(es) but NOT the last element from group of all classes. <asp:TextBox ID="TextBox1" runat="server" CssClass="class1" ></asp:TextBox> <asp:TextBox ID="TextBox2" runat="server" CssClass="class2" ></asp:TextBox> <asp:TextBox ID="TextBox3" runat="server" CssClass="class2" ></asp:TextBox> I want to select only TextBox1 and TextBox2, not TextBox3! selector should be something like this $("(.class1,.class1):not(:last)") or something like $(".class1,.class1").filter(":not(:last)") but of course none of it is working :) any sugestions? tnx in advance!

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  • Rails: Creating subfolders in model?

    - by keruilin
    I'm going to have a ton of subclasses, so want to organize them under a subfolder called stream. I added the following line to the environment.rb so that all classes in the subfolder would be loaded: Rails::Initializer.run do |config| ... config.load_paths += Dir["#{RAILS_ROOT}/app/models/*"].find_all { |f| File.stat(f).directory? } ... end I thought this would solve the issue in which by convention the model class is namespaced into an according module. However, when I try to call one of the classes called stream in the stream folder, I get the following error: NoMethodError: undefined method `new' for Stream:Module from (irb):28 from /usr/local/bin/irb:12:in `<main>' Here's the model for the parent and one child: class Stream end class EventStream < Stream end Any idea what the issue is?

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  • NoMethodError when trying to invoke helper method from Rails controller

    - by John Topley
    I'm getting a NoMethodError when trying to access a method defined in one of my helper modules from one of my controller classes. My Rails application uses the helper class method with the :all symbol as shown below: class ApplicationController < ActionController::Base helper :all . . end My understanding is that this should make all of my controller classes automatically include all of the helper modules within the app/helpers directory, therefore mixing in all of the methods into the controllers. Is this correct? If I explicitly include the helper module within the controller then everything works correctly.

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  • Using TDD: "top down" vs. "bottom up"

    - by Christian Mustica
    Since I'm a TDD newbie, I'm currently developing a tiny C# console application in order to practice (because practice makes perfect, right?). I started by making a simple sketchup of how the application could be organized (class-wise) and started developing all domain classes that I could identify, one by one (test first, of course). In the end, the classes have to be integrated together in order to make the application runnable, i.e. placing necessary code in the Main method which calls the necessary logic. However, I don't see how I can do this last integration step in a "test first" manner. I suppose I wouldn't be having these issues had I used a "top down" approach. The question is: how would I do that? Should I have started by testing the Main() method? If anyone could give me some pointers, it will be much appreciated.

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  • Writing Ruby Libraries - hiding methods from outside the module

    - by JP
    Hi all, I'm writing a Ruby library which has a module with a bunch of classes inside it. Many of these classes need to be usable and modifiable by calling scripts, but I don't want (some of) the initializers to be visible/callable: module MyLib class Control def initialize # They can use this end def do_stuff Helper.new('things') end end class Helper # Shouldn't be visible def initialize(what) @what = what end def shout @what end end end c = MyLib::Control.new h = c.do_stuff p h.shout # => "things" # ^ All of this is desired # v This is undesirable p MyLib::Helper.new('!') # => <MyLib::Helper @what='!'> If it's a simple thing, then I'd also appreciate the generated RDoc not even include the .new method for the Helper class either. Any ideas? Thanks for reading!

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  • Overload and hide methods in Java

    - by Marco
    Hi, i have an abstract class BaseClass with a public insert() method: public abstract class BaseClass { public void insert(Object object) { // Do something } } which is extended by many other classes. For some of those classes, however, the insert() method must have additional parameters, so that they instead of overriding it I overload the method of the base class with the parameters required, for example: public class SampleClass extends BaseClass { public void insert(Object object, Long param){ // Do Something } } Now, if i instantiate the SampleClass class, i have two insert() methods: SampleClass sampleClass = new SampleClass(); sampleClass.insert(Object object); sampleClass.insert(Object object, Long param); what i'd like to do is to hide the insert() method defined in the base class, so that just the overload would be visible: SampleClass sampleClass = new SampleClass(); sampleClass.insert(Object object, Long param); Could this be done in OOP?

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  • Constructors with inheritance in c++

    - by Crystal
    If you have 3 classes, with the parent class listed first shape- 2d shapes, 3d shapes - circle, sphere When you write your constructor for the circle class, would you ever just initialize the parent Shape object and then your current object, skipping the middle class. It seems to me you could have x,y coordinates for Shape and initialize those in the constructor, and initialize a radius in the circle or sphere class, but in 2d or 3d shape classes, I wouldn't know what to put in the constructor since it seems like it would be identical to shape. So is something like this valid Circle::Circle(int x, int y, int r) : Shape(x, y), r(r) {} I get a compile error of: illegal member initialization: 'Shape' is not a base or member So I wasn't sure if my code was legal or best practice even. Or if instead you'd have the middle class just do what the top level Shape class does TwoDimensionalShape::TwoDimensionalShape(int x, int y) : Shape (x, y) {} and then in the Circle class Circle::Circle(int x, int y, int r) : TwoDimensionalShape(x, y), r(r) {}

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  • C++ abstract class template + type-specific subclass = trouble with linker

    - by user333279
    Hi there, The project in question is about different endpoints communicating with each other. An endpoint sends events (beyond the scope of the current problem) and can process incoming events. Each event is represented in a generic object as follows: #pragma interface ... // some includes template<typename T> class Event { public: Event(int senderId, Type type, T payload); // Type is an enum Event(int senderId, Type type, int priority, T payload); virtual ~Event(); virtual int getSenderId(); virtual int getPriority(); virtual T getPayload(); void setPriority(const int priority); protected: const int senderId; const Type type; const T payload; int priority; }; It has its implementing class with #pragma implementation tag. An endpoint is defined as follows: #pragma interface #include "Event.h" template<typename T> class AbstractEndPoint { public: AbstractEndPoint(int id); virtual ~AbstractEndPoint(); virtual int getId(); virtual void processEvent(Event<T> event) = 0; protected: const int id; }; It has its implementing class too, but only the constructor, destructor and getId() are defined. The idea is to create concrete endpoints for each different payload type. Therefore I have different payload objects and specific event classes for each type, e.g. Event<TelegramFormatA>, Event<TelegramFormatB> and ConcreteEndPoint for TelegramFormatA, ConcreteEndPoint for TelegramFormatB respectively. The latter classes are defined as class ConcreteEndPoint : AbstractEndPoint<TelegramFormatA> { ... } I'm using g++ 4.4.3 and ld 2.19. Everything compiles nicely, but the linker complaints about undefined references to type-specific event classes, like Event<TelegramFormatA>::Event(....) . I tried explicit instantiation using template class AbstractEndPoint<TelegramFormatA>; but couldn't get past the aforementioned linker errors. Any ideas would be appreciated.

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  • IDisposable, does it really matter

    - by adrianm
    Coming from C/C++ a long time ago I still have a habit of ensuring that all resources are cleaned up correctly. I always ensure Dispose is called on IDisposable classes and implement Dispose patterns in my classes containing disposable objects. However, in my environment I'm more or less the only one doing this. Others just don't understand what I'm doing and think my code is more difficult to understand. They just create database connections, open streams etc without calling Close or Dispose. Sometimes they set a local or member variable to "Nothing" at the end of a method (guess their background). My problem is that their code works just as well as mine. Code that over time creates thousands of database connection objects just works. So, ignoring any arguments about code correctness, following guidelines etc, does IDiposable really matter? Has anyone actually ran out of resources from not Disposing objects?

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  • Setting new class variables inside a module

    - by Sean McCleary
    I have a plugin I have been working on that adds publishing to ActiveRecord classes. I extend my classes with my publisher like so: class Note < ActiveRecord::Base # ... publishable :related_attributes => [:taggings] end My publisher is structured like: module Publisher def self.included(base) base.send(:extend, ClassMethods) @@publishing_options = [] # does not seem to be available end module ClassMethods def publishable options={} include InstanceMethods @@publishing_options = options # does not work as class_variable_set is a private method # self.class_variable_set(:@@publishing_options, options) # results in: uninitialized class variable @@publishing_options in Publisher::ClassMethods puts "@@publishing_options: #{@@publishing_options.inspect}" # ... end # ... end module InstanceMethods # results in: uninitialized class variable @@publishing_options in Publisher::InstanceMethods def related_attributes @@publishing_options[:related_attributes] end # ... end end Any ideas on how to pass options to publishable and have them available as a class variable?

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  • What is the order of loading the CSS files in a HTML page ?

    - by Purushotham
    I want to know the order of loading the CSS files in a HTML page. My actual requirement is like this: I have more than 10 CSS files in my application. I am importing some 3 to 4 CSS files in each HTML page. The problem is I have duplicate classes that defined in some CSS files. That means I override some of the CSS classes in the CSS files. In some pages it behaves correctly. In some pages it behaves wrongly. I have inline styles defined for some of the DIVs in HTML page also. I am keeping CSS class for that DIVs also. Can anyone know which one will take higher priority or which one loads first ?

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  • Vector of objects

    - by Paul
    I've got a abstract class class A { public: virtual void somefunction() = ; }; and some different classes that inherit this class: class Ab { public: void somefunction(); }; etc. I want to make a vector containing some objects of these classes (how many depends on input parameters) so I can access these easily later. However I'm a bit lost on how to do this. My best idea is vector<A> *objectsVector; Ab AbObject; objectsVector.push_back(AbObject); However this gives me a huge amout of errors from various .h files in /usr/include/c++ How should i solve this?

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  • jQuery: I need something like ':visible' that works even if the parent is display=none

    - by Master Morality
    I have a list where elements are hidden for multiple reasons, each corresponding to a css class i.e: <style> .filteredOut { display: none; } .somethingElse { display : none; } ... </style> I want to apply alternating css classes via .filter(':even').addClass('even') but only to classes that are visible. The problem is that the parent is hidden when this happens so .filter(':visible') returns 0 elements. I need something like .filter(':visibileEventIfParentIsNot') Further more, I'd rather not have to call a function with this in it every time I call a function that changes what's visible in a list. This may be a pipe dream, but is there a way to do this ala live() or something similar? I'm open to off the wall ideas.

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