UITextField限制字数的方法

参考博客：http://www.oschina.net/code/snippet_54100_8632

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;

{

if ([string isEqualToString:@"\n"])

{

return YES;

}

NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string]; //关键代码。将新输入的内容与原内容合并



if (self.myTextField == textField)

{

if ([toBeString length] > 20) {

textField.text = [toBeString substringToIndex:20]; //总内容超过限制字数20，则截取前20个字符

UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:nil message:@"超过最大字数不能输入了" delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil] autorelease];

[alert show];

return NO;

}

}

return YES;

}