发送短信验证码按钮点击倒数计时

rac_sms_send_btn

send.rac_command = [[RACCommand alloc] initWithSignalBlock:^RACSignal *(id input) {
        NSDate *start = [NSDate date];
        [send setAttributedTitle:[[NSAttributedString alloc] initWithString:[NSString stringWithFormat:@"%f s", 5.f]
                                                            attributes:@{
                                                                         NSFontAttributeName:[UIFont fontWithName:@"STHeitiSC-Medium" size:16],
                                                                         NSForegroundColorAttributeName:[UIColor blackColor]
                                                                         }] forState:UIControlStateNormal];
        return [send rac_liftSelector:@selector(setAttributedTitle:forState:)
                   withSignals:
                [[[[RACSignal interval:1 onScheduler:[RACScheduler currentScheduler]]
                  startWith:start]
                  takeWhileBlock:^BOOL(id x) {
                      return ![send.titleLabel.attributedText.string isEqualToString:@"测试"];
                  }]
                 map:^id (NSDate *value) {
                     NSTimeInterval timer = [[NSDate date] timeIntervalSinceDate:start];
                     if (timer >= 5) {
                         return [[NSAttributedString alloc] initWithString:@"测试"
                                                                attributes:@{
                                                                             NSFontAttributeName:[UIFont fontWithName:@"STHeitiSC-Medium" size:16],
                                                                             NSForegroundColorAttributeName:[UIColor blackColor]
                                                                             }];
                     }
                     return [[NSAttributedString alloc] initWithString:[NSString stringWithFormat:@"%d s", (int)ceil(5-timer)]
                                                            attributes:@{
                                                                         NSFontAttributeName:[UIFont fontWithName:@"STHeitiSC-Medium" size:16],
                                                                         NSForegroundColorAttributeName:[UIColor blackColor]
                                                                         }];
                 }],
                [RACSignal return:@(UIControlStateNormal)],
                nil];
    }];