" [NSBigMutableString substringWithRange：]：范围{0,10}越界;字符串长度9“撤消错误 [英] "[NSBigMutableString substringWithRange:]: Range {0, 10} out of bounds; string length 9" error with Undo

问题描述

当我尝试在 UISearchBar 上执行撤消操作时，我的应用崩溃了。在我的应用程序中，我有代码阻止在搜索栏上输入'％'符号，为此，它将textDidChange方法中的％替换为@，如下所示：

My app crashes when I try to do undo on UISearchBar. In my app I have code to prevent entering a '%' sign on the search bar and for doing this it replaces a % to @"" in textDidChange method as below:

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
   self.searchBar.text = [searchText stringByReplacingOccurrencesOfString:@"%" withString:@""];
}

因此，如果我输入文本abc％xyz，则可以看到最终文本搜索栏将是'abcxyz'。不，当我点击撤消时，我看到'xyz'被清除了，我仍然在搜索栏上看到'abc'，而不是一次性清除'abcxyz'。

So if I type text "abc%xyz", the final text visible on search bar would be 'abcxyz'. No when I click undo, I see 'xyz' gets cleared and I still see 'abc' on the search bar instead of clearing 'abcxyz' all at one go.

现在，如果我再次点击撤消清除'abc'我的应用程序崩溃 [NSBigMutableString substringWithRange：]：范围超出范围错误。

Now if I click undo again to clear 'abc' my app crashes with [NSBigMutableString substringWithRange:]: Range out of bounds error.

我假设即使'％'被@替换，撤销管理器仍可能持有它，因此范围越界。

I am assuming that even though '%' gets replaced by @"", the undo manager might still be holding it and hence the range is going out of bounds.

我在 textDidChange [searchBar.undoManager removeAllActions]; >我用@替换％，但它没有帮助。以下是代码：

I tried [searchBar.undoManager removeAllActions]; in textDidChange after I replace % with @"", but it didn't help. Here is the code:

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
    {
       self.searchBar.text = [searchText stringByReplacingOccurrencesOfString:@"%" withString:@""];
      [searchBar.undoManager removeAllActions];
    }

问题： 以前有人遇到类似问题吗？如何处理撤消？

Question: Anybody faced similar issue before? How do I handle the undo?

推荐答案

您应该使用此委托方法：

You should be using this delegate method instead:

        - (BOOL)searchBar:(UISearchBar *)searchBar
  shouldChangeTextInRange:(NSRange)range
          replacementText:(NSString *)text

如果replacementText等于％，则返回NO。这将阻止用户首先使用它，因为它不会更新文本字段，这应该可以解决您遇到的撤消问题。

And just return NO in case the replacementText is equal to "%". This will prevent the user from using it in the first place as it won't update the textfield, which should fix the undo issue you're having.

解决方案

- (BOOL)searchBar:(UISearchBar *)searchBar shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    if([text isEqualToString:@"%"]) {
        return NO;
    }

    return YES;
}

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