btn.currentTitle

判断字符串是否为空

str.length == 0

隐藏button

btn.hidden = YES;

延迟执行

[self performSelector:@selector() withObject:nil afterDelay:1.5];

UITextField笔记

UITextField *textField = [[UITextField alloc] init];
textField.delegate = self;
//响应键盘
[textField becomeFirstResponder];
//取消响应键盘
[textField resignFirstResponder];
//
[self.view endEditing:YES];

ImageView自适应图像大小

[self.imageView sizeTofit:image];