ReactiveCocoa系列-隐藏显示placehold

        //创建textField获得焦点信号,当信号发生时返回@YES
        RACSignal *didBeginEditingSignal = [[self rac_signalForSelector:@selector(textFieldDidBeginEditing:) fromProtocol:@protocol(UITextFieldDelegate)] mapReplace:@YES];
        
        //创建textField失去焦点信号,当信号发生时返回@NO
        RACSignal *didEndEditingSignal = [[self rac_signalForSelector:@selector(textFieldDidEndEditing:) fromProtocol:@protocol(UITextFieldDelegate)] mapReplace:@NO];
        
        //合并两种信号到一个信号
        RACSignal *userTextSignal = [RACSignal merge:@[didBeginEditingSignal,didEndEditingSignal]];
        
        //doNext是信号发生时注入的边界触发.hiden为label的属性
        RAC(placehold,hidden) = [userTextSignal doNext:^(id x) {
            NSLog(@"toggle placehold. %@",x);
        }];

（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!