这篇博客主要讲限制输入长度的问题，前几天有人问我这个问题，说限制长度会出现无法删除问题，于是正好一块发出来给大家看看。textField的缩进，一张背景图片搞定的事，我这里用了leftView纯属附带。

好了废话少说，贴代码，很简单，大家一看便知。

//先创建一个textField 和 一个button。

#import "ViewController.h"

@interface ViewController ()<UITextFieldDelegate> {
    
    UITextField *currentTextFeild;
    UIButton    *touchButton;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UITextField *textFields = [[UITextField alloc] initWithFrame:CGRectMake(15, 50, self.view.bounds.size.width-15*2, 40)];
    textFields.backgroundColor = [UIColor brownColor];
    textFields.layer.cornerRadius = 5;
    textFields.leftView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 10, 40)];
    textFields.leftViewMode = UITextFieldViewModeAlways;//这两行是为了不让Text太贴textField的左边
    textFields.placeholder = @"请输入手机号";
    textFields.delegate = self;
    [self.view addSubview:textFields];
    currentTextFeild = textFields;
    
    UIButton *enableButton = [UIButton buttonWithType:UIButtonTypeCustom];
    enableButton.frame = CGRectMake(15, 100, self.view.bounds.size.width-15*2, 40);
    enableButton.layer.cornerRadius = 5;
    enableButton.backgroundColor = [UIColor grayColor];
    [enableButton setTitle:@"没内容不可点击" forState:UIControlStateNormal];
    [enableButton setTitle:@"可以按了" forState:UIControlStateSelected];
    [enableButton setTitle:@"按下去了" forState:UIControlStateHighlighted];
    enableButton.enabled = NO;
    [enableButton addTarget:self action:@selector(btnClick) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:enableButton];
    touchButton = enableButton;
}

- (void)btnClick {
    
    
}

//设置textField代理 

#PRagma mark -  UITextFieldDelegate
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {
    
    return YES;
}

- (void)textFieldDidEndEditing:(UITextField *)textField {
    
    
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    
    //用来判断是否可以继续输入， - range.length是为了判断是否可以删除
    NSInteger currentLength = textField.text.length - range.length + string.length;
    if (currentLength > 11) {
        
        return NO;
    }
    
    //判断按钮是否可以enable = YES
    if (currentTextFeild.text && currentTextFeild.text.length > 0 && currentLength > 0) {
        
        touchButton.enabled = YES;
        touchButton.selected = YES;
    }else {
        
        touchButton.enabled = NO;
        touchButton.selected = NO;
    }
    
    if (currentLength <= 0) {
        
        touchButton.enabled = NO;
        touchButton.selected = NO;
    }
    
    return YES;
}

- (BOOL)textFieldShouldClear:(UITextField *)textField {
    
    if (currentTextFeild.tag == 11 || currentTextFeild.tag == 12) {
        //手机号
        touchButton.enabled = NO;
        touchButton.selected = NO;;
    }
    
    return YES;
}

- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    
    [textField resignFirstResponder];
    
    return YES;
}

 大家看了代码，差不多就明白了。