Re: Basic info about outlets

FROM : Torsten Curdt
DATE : Thu May 15 15:21:04 2008

Hm ...I would have though the runtime would just do dependency/
reference injection.
And the procedural code has a (hidden) reference/parameter to the 
object instance - that would be "self".

cheers
--
Torsten

On May 15, 2008, at 13:53, Graham Cox wrote:

> Yep, you're basically correct, sounds right to me.
>
> When the nib is loaded, <documentWindow> will point to ("refer to") 
> the window object.
>
> someMethod is able to simply use the variable <documentWindow> 
> because that is an instance variable of the MyDocument object, and 
> all methods of MyDocument are able to use the object's ivars as if 
> they were locally declared. This is one of the main reasons that OOP 
> is a useful way to program.
>
> so someMethod could then message the window itself, for example:
>
> - (void) someMethod
> {
>    // set a property:
>
>    [documentWindow setTitle:@"Arrooooggahh!!"];
>
>    // read a property:
>
>    NSRect wFrame = [documentWindow frame];
> }
>
>
> If you're asking *how* this works, the answer lies in the Obj-C 
> runtime. Basically all of an object's methods are implicitly passed 
> a pointer to the object itself (self) as a hidden parameter to the 
> function that the method is wrapping. The compiler thus generates 
> code that makes use of this implicit parameter, so the real code is 
> really doing the equivalent of:
>
> void someMethod( NSDocument* self )
> {
>    setTitle( self->documentWindow, @"string" );
> }
>
> underneath, it's all procedural ;-) (I'm simplifying, it's not 
> literally quite like this, Find out more here: file:///Developer/Documentation/DocSets/com.apple.ADC_Reference_Library.CoreReference.docset/Contents/Resources/Documents/documentation/Cocoa/Reference/ObjCRuntimeRef/index.html)
> .
>
> hth,
>
>
> G.
>
>
>
> On 15 May 2008, at 9:30 pm, John Love wrote:
>

>> I *think* I understand about outlets and actions .. but now I am 
>> not so
>> sure.
>>
>> Specifically, if I set (NSWindow *)documentWindow as an Outlet in 
>> my main
>> nib and I declare in MyDocument.h file:
>>
>> interface MyDocument:NSDocument {
>>        IBOutlet NSWindow *documentWindow;
>> }
>> ...
>>
>> - (void) someMethod:documentWindow;
>>
>> and in MyDocument.m file:
>>
>> - (void) someMethod {
>>    // some operation that accesses a property of documentWindow
>> }
>>
>> Okay, documentWindow is typed as a outlet in the main nib and in the
>> interface,.h, file ... and I have control-dragged from the 
>> FileOwner to the
>> title bar of the Window, selecting "documentWindow" as the Outlet. 
>> But,
>> just exactly HOW does the actual documentWindow object get passed 
>> so that
>> someMethod can look at one of its properties?
>>
>> This question is oriented to "behind the scenes".
>>
>> Thanks in advance>
>>
>> John Love
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