一、UITextView

1. 在@interface中宣告代理

      @interface MyViewController : UIViewController <UITextViewDelegate>

 2. 設定UITexView的delegate，可以在viewDidLoad方法中實現，也可以在nib檔案（或是storyboard）中實現。

      textView.delegate = self;

3. 實現代理方法。

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    textLabel.hidden =YES;
    
    NSString *string = [textView.text stringByReplacingCharactersInRange:range withString:text];
    
    if ([string length] >= 250)
    {
        string = [string substringToIndex:250];
        
        textView.text = string;
        
        CharNumber2.text =[NSString stringWithFormat:@"不可以輸入更多"];
        

        return NO;

    }else{
        
        CharNumber2.text =[NSString stringWithFormat:@"你還可以輸入%d字",250 - string.length];
        
        if ([string length] == 0)
        {
            textLabel.hidden = NO;
        }
        else if ([string length] > 0 && [string length] < 250)
        {
            
        }
    }
 

    if ([text isEqualToString:@"\n"])

    {

        [self fankui];

        return NO;

    }
    return YES;
}

二、UITextField

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

{

    if (textField == self.titleTextField) {

        NSString *string0 = [textField.text

stringByReplacingCharactersInRange:range withString:string];

        if ([string0 length] > 30)

        {

            string0 = [string0 substringToIndex:30];

            self.titleTextField.text = string0;

            self.titleNumLabel.text = [NSString stringWithFormat:@"%d/30",string0.length];

            self.titleNumLabel.textColor = kUIColorFromRGB(0xb7babb);

            return NO;

        }else{

            self.titleNumLabel.text = [NSString stringWithFormat:@"%d/30",string0.length];

            if (string0.length < 6 || string0.length > 30) {

                self.titleNumLabel.textColor = [UIColor redColor];

            }else{

                self.titleNumLabel.textColor = kUIColorFromRGB(0xb7babb);

            }

        }

    }

return YES;

}