Objective-C Associative References(續)

Objective-C Associative References(關聯引用) 一篇文章，今天在看KVC方面的文章，所以就想到結合一起再講明白一點，更加結合實際一點

CAKeyframeAnimation *animation=[CAKeyframeAnimation animationWithKeyPath:@"position"];keyPosi.path=path;keyPosi.delegate=self;[label.layer addAnimation:animation forKey:@"position"];

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{}

[animation setValue:view forKey:@"xx"];

然後我就修改回調方法：

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{    if (flag) {        UIView *vie=[anim valueForKey:@"xx"];        [vie removeFromSuperview];    }}

這樣正確嘛？

*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<NSObject 0xf65f090> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key xx.'

Invoked by setValue:forKey: when it finds no property - ()setValue:()value forUndefinedKey:(NSString *DiscussionSubclasses can   method to handle the request  some other way. The  implementation raises an NSUndefinedKeyException.

和

#import <objc/runtime.h>@interface NSObject (KVC)- (id)valueForUndefinedKey:(NSString *)key;- (void)setValue:(id)value forUndefinedKey:(NSString *)key;@end@implementation NSObject(KVC)- (id)valueForUndefinedKey:(NSString *)key{    return objc_getAssociatedObject(self, key);}- (void)setValue:(id)value forUndefinedKey:(NSString *)key{    if ([value isKindOfClass:[NSString class]]) {        objc_setAssociatedObject(self, key, value, OBJC_ASSOCIATION_COPY_NONATOMIC);    }else{        objc_setAssociatedObject(self, key, value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);    }}@end

這樣就實現了目的。