今天做项目的时候，有个需求，点击按钮，就在特定的编辑框输入按钮中的文字，一开始我还以C++的思想来写，先获取光标的位置，然后在判断是否在那个编辑框，进行输入。后来我旁边的同事看到了直接教我用代理方法，因为接触iOS没多久，也不清楚<UITextFieldDelegate>的用法。非常感谢我同事。

1、代理<UITextFieldDelegate>

@interface idiom_ViewController ()<UITextFieldDelegate>
{
    UITextField * _selectTf;
    NSArray *UIButton_array;
}
@property (weak, nonatomic) IBOutlet UITextField *first_idiom;
@property (weak, nonatomic) IBOutlet UITextField *second_idiom;
@property (weak, nonatomic) IBOutlet UITextField *third_idiom;

- (void)viewDidLoad {
    [super viewDidLoad];
    //实现UITextFieldDelegate的协议
    _first_idiom.delegate=self;
    _second_idiom.delegate =self;
    _third_idiom.delegate =self;
    //点击编辑框隐藏软键盘
    _first_idiom.inputView =[UIView new];
    _second_idiom.inputView =[UIView new];
    _third_idiom.inputView =[UIView new];
    //创建手势识别对象并监听手势
    UITapGestureRecognizer * tap =[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapAction)];
    [self.view addGestureRecognizer:tap];
    // Do any additional setup after loading the view from its nib.
}

//失去焦点
-(void)tapAction{
    [self.view endEditing:YES];
}

-(void)textFieldDidEndEditing:(UITextField *)textField{
    _isBeginTf =NO;
}

-(void)textFieldDidBeginEditing:(UITextField *)textField
{
    _isBeginTf =YES;
    _selectTf =textField;
}

2、按钮点击事件-编辑框输入按钮文字

- (void)button_word:(UIButton *)btn
{
    if (!_isBeginTf) {
        return;
    }
    _selectTf.text = [NSString stringWithFormat:@"%@%@",_selectTf.text,btn.titleLabel.text];
    btn.userInteractionEnabled =NO;
    btn.backgroundColor =[UIColor lightGrayColor];
}

3、删除按钮事件

- (IBAction)goBackButtonAction:(id)sender {
    if (!_isBeginTf) {
        return;
    }
    
    if ([_selectTf.text isEqualToString:@""]) {
        return;
    }
    //获取编辑框最后一个文字
    NSString *gaBackStr =[_selectTf.text substringWithRange:NSMakeRange(_selectTf.text.length-1, 1)];
    //获取编辑框length -1的文字
    _selectTf.text =[_selectTf.text substringToIndex:_selectTf.text.length -1];
    
    for (int i=0; i<12; i++) {
         UIButton *btn= UIButton_array[i];
        //判断删除的文字和按钮中的文字是否相同
        if ([btn.titleLabel.text isEqualToString:gaBackStr]) {
            //相同，按钮从不可点击变为可点击，颜色改变
            btn.userInteractionEnabled =YES;
            btn.backgroundColor =[UIColor orangeColor];
            return;
        }
    }
    
}