目标c中字符限制的委托

@interface MyViewController : UIViewController <UITextFieldDelegate>

@property (nonatomic, strong) UITextField *textField;

@end

@implementation MyViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.textField = [[UITextField alloc] initWithFrame:CGRectMake(50, 50, 200, 30)];
    self.textField.delegate = self;
    [self.view addSubview:self.textField];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    // 获取当前输入框中的文本
    NSString *text = [textField.text stringByReplacingCharactersInRange:range withString:string];
    
    // 设置字符限制为10个字符
    NSUInteger limit = 10;
    
    // 判断字符数量是否超过限制
    if (text.length > limit) {
        return NO; // 不允许输入
    }
    
    return YES; // 允许输入
}

@end