Can D be cute? (Qt)

[Justin Johansson]

Marianne Gagnon wrote:
> Hi Justin,
> 
> looking at QtD, it seems like it can be done :
> 
> In file http://www.dsource.org/projects/qtd/browser/demos/browser/browsermainwindow.d
> 
>         m_historyHome.triggered().connect(&this.slotHome);
> 
>         // ...
> 
>  	public:
> 	
>  	    void slotHome()
>  	    {
>  	        // ...
> 	    }
> 
> I however believe that this kind of delegate-connection can also be performed in C++ (with templates?). Maybe Qt developers simply continue using the MOC because they don't want to break backwards compatibility.
> 
> -- Auria

Maybe to a small degree but it seems to me that the Qt Meta-Object 
Compiler does more than just support signal and slot connections.  There 
are a number of "C++ extension" that can go in a class declaration like 
Q_OBJECT, Q_PROPERTY, Q_ENUMS, Q_CLASSINFO.

e.g. as below from from http://doc.trolltech.com/4.4/moc.html

The MOC mechanism makes it trivial to expose classes in Qt to scripting 
with QtScript (basically Qt version of JavaScript).

I haven't dug deep enough into QtD to know how it fares in the scripting 
arena though.

Cheers
Justin Johansson


<QtDocumentation>

In addition to the signals and slots shown above, moc also implements 
object properties as in the next example. The Q_PROPERTY() macro 
declares an object property, while Q_ENUMS() declares a list of 
enumeration types within the class to be usable inside the property system.

In the following example, we declare a property of the enumeration type 
Priority that is also called priority and has a get function priority() 
and a set function setPriority().

  class MyClass : public QObject
  {
      Q_OBJECT
      Q_PROPERTY(Priority priority READ priority WRITE setPriority)
      Q_ENUMS(Priority)

  public:
      enum Priority { High, Low, VeryHigh, VeryLow };

      MyClass(QObject *parent = 0);
      ~MyClass();

      void setPriority(Priority priority);
      Priority priority() const;
  };

The Q_FLAGS() macro declares enums that are to be used as flags, i.e. 
OR'd together. Another macro, Q_CLASSINFO(), allows you to attach 
additional name/value pairs to the class's meta-object:

  class MyClass : public QObject
  {
      Q_OBJECT
      Q_CLASSINFO("Author", "Oscar Peterson")
      Q_CLASSINFO("Status", "Active")

  public:
      MyClass(QObject *parent = 0);
      ~MyClass();
  };

</QtDocumentation>