iOS7中UITextView限制字符的坑

最近做的app因为涉及到适配iOS7测试阶段遇到了很多的bug，不得不说iOS7适配非常的坑爹，其中UITextView限制输入字符在iOS7中非常特殊，高版本限制字符代码如下：

- (void)textViewDidChange:(UITextView *)textView1 {
    NSInteger number = [textView1.text length];
    NSInteger maxLength = 30;
    if (textView1.text.length > maxLength) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"字符个数不能大于30" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];
        alert.tag = 100;
        [alert show];
        textView1.text = [textView.text substringToIndex:30];
        number = 30;
    }
}

这段代码在高版本机器上测试没问题，但是一旦在iOS7上运行时就会报错：

Terminating app due to uncaught exception 'NSRangeException', reason: 'NSMutableRLEArray replaceObjectsInRange:withObject:length:: Out of bounds'

github上查阅资料找到了一种解决办法，通用iOS7以上所有系统版本：

- (void)textViewDidChange:(UITextView *)textView1 {
    NSInteger number = [textView1.text length];
    NSInteger maxLength = 30;
    if (textView1.markedTextRange == nil && textView1.text.length > maxLength) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"字符个数不能大于30" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];
        alert.tag = 100;
        [alert show];
        textView1.text = [textView.text substringToIndex:30];
        number = 30;
    }
}