NSRange崩溃的应用程序 [英] NSRange crashing app

问题描述

我遇到NSRange的问题，导致我的应用在textview为空时崩溃。我正在使用一个自定义键盘上有一个退格键，它在这里调用此代码...

I have an issue with NSRange that is causing my app to crash when textview is empty. I am using a custom keyboard that has a backspace button on it and it calls this code here...

if ([self.myChart isFirstResponder]) {
    NSRange currentRange = myChart.selectedRange;
    if (currentRange.length == 0) {
        currentRange.location--;
        currentRange.length++;
    }
    myChart.text = [myChart.text stringByReplacingCharactersInRange:currentRange withString:[NSString string]];
    currentRange.length = 0;
    myChart.selectedRange = currentRange;

    NSLog(@"%d", NSNotFound);
}

如果我在textview中有文字，这对于删除一个字符非常有用但是当我到达textview的开头并且没有更多的字符时，我得到异常并崩溃...

If I have text in the textview this works perfectly for removing one character at a time however when I get to the beginning of the textview and there are no more characters, I get the exception and crash...

*** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFString replaceCharactersInRange:withString:]: Range or index out of bounds'

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我的目标是让退格功能停止。我明白为什么它会崩溃，但我不知道如何解决它。我试过没有运气对NSNotFound进行评估。

---

My goal is to have the backspace function stop. I understand why it is crashing but I don't know how to resolve it. I have tried evaluating it against NSNotFound without luck.

任何想法都会非常感激！

Any ideas would be much appreciated!

推荐答案

你应该检查字段中是否有文字，即：

You should check that there is text in the field, ie:

if ( myChart.text.length > 0 )

并检查以确保您没有尝试访问位置-1 ：

and also check to make sure you aren't trying to access location -1:

if ( currentRange.location >= 0 )

所以你的代码看起来像

if ([self.myChart isFirstResponder] && myChart.text.length > 0 ) {
    NSRange currentRange = myChart.selectedRange;
    if (currentRange.length == 0) {
        currentRange.location--;
        currentRange.length++;
    }
    if ( currentRange.location >= 0 )
    {
        myChart.text = [myChart.text stringByReplacingCharactersInRange:currentRange withString:[NSString string]];
        currentRange.length = 0;
        myChart.selectedRange = currentRange;

        NSLog(@"%d", NSNotFound);
    }
}

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