Re: QtDesigner/Glade

[Chris Hanson]

At 2:30 PM +0000 1/16/02, Richard Dale wrote:
> Qt Designer assumes event handling would be done in the Qt style, which is
> much the same as the AppKit - ie you subclass a widget to do event handling
> rather than add event listeners like Java.

This isn't at all what AppKit event handling is like.

Well, I suppose it depends what you mean by "event handling."

If you mean "you subclass NSResponder to handle particular low-level 
NSEvents (mouse clicks, keystrokes, etc.) or pass them up the chain" 
then what you've said is correct.

However, if you mean "you subclass NSButton to handle when the user 
clicks on a button" then it's completely incorrect.  In the AppKit, 
all NSControl implements the target-action design pattern for its 
subclasses.  You use -[NSControl setTarget:] to set the object that 
should receive an action message and -[NSControl setAction:] to set 
the action the target should receive.  Actions are invoked by 
low-level human interface events, but you only truly need to worry 
about these events when you're implementing a brand new type of 
control.

> Yes, the AppKit itself doesn't have any runtime support for outlets and
> actions, that is only done in InterfaceBuilder I think.

Incorrect.  The target-action design pattern is implemented by 
NSControl, and the setting outlets in an object can be done via 
key-value coding.

It's true that Interface Builder parses header files to determine 
what the outlet instance variables and action methods in a class are; 
there's no runtime support for getting an array of SELs corresponding 
to action methods, or for getting an NSArray of outlet keys.  But the 
nib loading code can use built in AppKit and FoundationKit 
functionality to perform the outlet and action manipulations that are 
recorded in a nib file.

  -- Chris

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Chris Hanson                      |  Email: cmh@bDistributed.com
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