ReactiveCocoa

那我们来看一看这最简单的例子，

// When self.username changes,logs the new name to the console.
//
// RACObserve(self,username) creates a new RACSignal that sends the current
// value of self.username,then the new value whenever it changes.
// -subscribeNext: will execute the block whenever the signal sends a value.
[RACObserve(self,username) subscribeNext:^(NSString *newName) {
    NSLog(@"%@",newName);
}];

接下来，看看内部具体的代码

NSObject+RACPropertySubscribing.h

#define RACObserve(TARGET,KEYPATH) 
    [(id)(TARGET) rac_valuesForKeyPath:@keypath(TARGET,KEYPATH) observer:self]

- (RACSignal *)rac_valuesFor
	KeyPath:(NSString *)keyPath 
	observer:(NSObject *)observer 
{
	return [[[self
		rac_valuesAndChangesForKeyPath:keyPath options:NSKeyValueObservingOptionInitial observer:observer]
		map:^(RACTuple *value) {
			// -map: because it doesn't require the block trampoline that -reduceEach: uses
			return value[0];
		}]
		setNameWithFormat:@"RACObserve(%@,%@)",self.rac_description,keyPath];
}

- (RACSignal *)rac_valuesAndChangesForKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options observer:(NSObject *)observer {

	return [self rac_observeKeyPath:keyPath options:options observer:observer block:^(id value,NSDictionary *change,BOOL causedByDealloc,BOOL affectedOnlyLastComponent) {
		[subscriber sendNext:RACTuplePack(value,change)];
	}];

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!