iOS textfield 限制輸入字數長度

iOS textfield限制輸入的最大長度

 [self.textFiled addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

-(void)textFieldDidChange:(UITextField *)textField
{
    CGFloat maxLength = 14;
    NSString *toBeString = textField.text;
    
    //獲取高亮部分
    UITextRange *selectedRange = [textField markedTextRange];
    UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
    if (!position || !selectedRange)
    {
        if (toBeString.length > maxLength)
        {
            NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:maxLength];
            if (rangeIndex.length == 1)
            {
                textField.text = [toBeString substringToIndex:maxLength];
            }
            else
            {
                NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, maxLength)];
                textField.text = [toBeString substringWithRange:rangeRange];
            }
        }
    }
}