监听到UITextField的文本文字改变的3种方法

1.代理（不推荐）
    _accountField.delegate = self;

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSLog(@"shouldChangeCharactersInRange--%@",textField.text);
    return YES;
}
 
  
 
  
    // 2.通知
//    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChange) name:UITextFieldTextDidChangeNotification object:_accountField];
    
 
  
 
  
 
   
    // 3.addTarget
    [_accountField addTarget:self action:@selector(textChange) forControlEvents:UIControlEventEditingChanged];
    [_pwdField addTarget:self action:@selector(textChange) forControlEvents:UIControlEventEditingChanged]
  // 1.代理