Re: Basic info about outlets
Re: Basic info about outlets
- Subject: Re: Basic info about outlets
- From: Torsten Curdt <email@hidden>
- Date: Thu, 15 May 2008 15:21:04 +0200
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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