关于每个对象多个代表的问题?答案之一提出了有趣的解决方案(至少对于我天真的眼睛):创建一个“委托拆分器”,允许一个对象(在本例中为 UIScrollView)拥有多个委托(在本例中为 UIScrollViewDelegate)。
代码如下:
@interface DelegateSplitter : NSObject
-(void)addDelegate:(id)delegate;
-(void)addDelegates:(NSArray*)array;
@end
@interface DelegateSplitter()
@property NSMutableSet *delegates;
@end
@implementation DelegateSplitter
-(id)init
{
self = [super init];
_delegates = [NSMutableSet set];
return self;
}
-(void)addDelegate:(id)delegate
{
[_delegates addObject:delegate];
}
-(void)addDelegates:(NSArray *)array
{
[_delegates addObjectsFromArray:array];
}
-(void)forwardInvocation:(NSInvocation *)anInvocation
{
for (id delegate in _delegates)
{
if([delegate respondsToSelector:anInvocation.selector])
{
[anInvocation invokeWithTarget:delegate];
}
}
}
- (NSMethodSignature*) methodSignatureForSelector: (SEL) selector
{
NSMethodSignature *our = [super methodSignatureForSelector:selector];
NSMethodSignature *delegated = [[_delegates anyObject]
methodSignatureForSelector:selector];
return our ? our : delegated;
}
- (BOOL) respondsToSelector: (SEL) selector
{
return [[_delegates anyObject] respondsToSelector:selector];
}
这段代码的问题在于它创建了保留循环,并且与普通委托不同,您不能将其声明为
@property (assign) DelegateSplitter *splitter;
然而,它似乎是比包装器“更好”的解决方案。那么有没有办法避免保留周期?