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"
For the current version of Interface Builder, see
- (void)connectOutlet:(NSString
*)outletofSourceObject:(id)sourcetoDestinationObject:(id)destination
of the IBDocument class in the InterfaceBuilderKit framework.
In the current version of Interface Builder, the precise mechanism for
storing connection information is not documented and therefore considered an
implementation detail. However, in previous versions of Interface Builder, it
worked like the following:
There is/was a class called IBConnector which looked something like this
@interface IBConnector : NSObject <NSCoding>
{
id source;
NSString *outletName;
id destination;
}
- (void)setSource:(id)anObject;
- (void)setOutletName:(NSString *)aName;
- (void)setDestination:(id)anObject;
- (void)connect;
@end
When you drag a connection in IB, a new instance of IBConnector is created,
initialized with a source, outlet name, and destination accordingly, and
archived into the .nib file.
When the nib file is tested in IB or loaded into your application at
run-time, the IBConnector instances are unarchived just like every other object
in the nib. Once unarchived, each IBConnector instance's source and
destination instance variables are restored to a reference to the corresponding
unarchived objects. [That is just how archiving and unarchiving graphs of
objects works. Read up on archiving for details].
As part of the nib loading process but before -awakFromNib is sent to any
objects unarchived from the nib, the connect message is sent to each unarchived
IBConnection instance.
The -connect method of IBConnector is implemented something like this
- (void)connect
{
Ivar ivar = class_getInstanceVariable([source class], [outletName
UTF8String]);
object_setIvar(source , ivar, destination);
}
See
http://developer.apple.com/documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html
for information about class_getInstanceVariable() and object_setIvar(). The
source code for the runtime is also available.
Once the connections are all made, the IBConnector instances are no longer
needed and may be deallocated.
Then -awakeFromNib is called for every object unarchived from the nib and
incidentally also the "File's Owner" object. Because the connections were all
restored before -awakeFromNib, it is safe to use the connections in your
implementation of -awakeFromNib.
Does that answer you "behind the scenes" question ?
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