148 lines
3.1 KiB
Objective-C
148 lines
3.1 KiB
Objective-C
#import <Foundation/Foundation.h>
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// SourceBase will be the base class of Source. We'll pass a Source object into a
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// function as a SourceBase, and then see if the dynamic typing can get us through the KVO
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// goo and all the way back to Source.
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@interface SourceBase: NSObject
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{
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uint32_t _value;
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}
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- (SourceBase *) init;
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- (uint32_t) getValue;
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@end
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@implementation SourceBase
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- (SourceBase *) init
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{
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[super init];
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_value = 10;
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return self;
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}
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- (uint32_t) getValue
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{
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return _value;
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}
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@end
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// Source is a class that will be observed by the Observer class below.
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// When Observer sets itself up to observe this property (in initWithASource)
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// the KVO system will overwrite the "isa" pointer of the object with the "kvo'ed"
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// one.
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@interface Source : SourceBase
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{
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int _property;
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}
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- (Source *) init;
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- (void) setProperty: (int) newValue;
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@end
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@implementation Source
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- (Source *) init
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{
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[super init];
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_property = 20;
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return self;
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}
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- (void) setProperty: (int) newValue
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{
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_property = newValue; // This is the line in setProperty, make sure we step to here.
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}
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@end
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@interface SourceDerived : Source
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{
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int _derivedValue;
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}
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- (SourceDerived *) init;
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- (uint32_t) getValue;
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@end
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@implementation SourceDerived
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- (SourceDerived *) init
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{
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[super init];
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_derivedValue = 30;
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return self;
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}
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- (uint32_t) getValue
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{
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return _derivedValue;
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}
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@end
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// Observer is the object that will watch Source and cause KVO to swizzle it...
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@interface Observer : NSObject
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{
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Source *_source;
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}
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+ (Observer *) observerWithSource: (Source *) source;
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- (Observer *) initWithASource: (Source *) source;
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- (void) observeValueForKeyPath: (NSString *) path
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ofObject: (id) object
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change: (NSDictionary *) change
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context: (void *) context;
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@end
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@implementation Observer
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+ (Observer *) observerWithSource: (Source *) inSource;
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{
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Observer *retval;
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retval = [[Observer alloc] initWithASource: inSource];
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return retval;
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}
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- (Observer *) initWithASource: (Source *) source
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{
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[super init];
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_source = source;
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[_source addObserver: self
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forKeyPath: @"property"
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options: (NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld)
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context: NULL];
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return self;
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}
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- (void) observeValueForKeyPath: (NSString *) path
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ofObject: (id) object
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change: (NSDictionary *) change
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context: (void *) context
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{
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printf ("Observer function called.\n");
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return;
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}
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@end
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uint32_t
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handle_SourceBase (SourceBase *object)
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{
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return [object getValue]; // Break here to check dynamic values.
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}
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int main ()
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{
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Source *mySource;
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Observer *myObserver;
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NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
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mySource = [[SourceDerived alloc] init];
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myObserver = [Observer observerWithSource: mySource];
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[mySource setProperty: 5]; // Break here to see if we can step into real method.
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uint32_t return_value = handle_SourceBase (mySource);
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SourceDerived *unwatchedSource = [[SourceDerived alloc] init];
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return_value = handle_SourceBase (unwatchedSource);
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[pool release];
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return 0;
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}
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