关于每次UItextfield输入数字执行delegates

其实检听UITextField 在接收到每个字符时所执行某一个方法 是通过注册通知来实现的

[[NSNotificationCenter defaultCenter] addObserver:self
                                          selector:@selector(textChanged:)
                                              name:UITextFieldTextDidChangeNotification
                                            object:YOUR_TEXT_FIELD];

-(void)textChanged:(NSNotification *)notif {
    //to do your logic
}