需要帮助修复内存泄漏 - NSMutableString [英] Need help fixing memory leak - NSMutableString

问题描述

首先，代码如下：

- （NSString *）randomizeHint：（NSString *）wordToShuffle {

NSMutableString * outputstring = [NSMutableString stringWithCapacity：[wordToShuffle length]] ;
NSMutableSet * usedNumberSet = [NSMutableSet setWithCapacity：[wordToShuffle length]];

for（int i = 0; i <[wordToShuffle length]; i ++）{
int randomnum = arc4random（）％[wordToShuffle length];

while（[usedNumberSet containsObject：[NSNumber numberWithInt：randomnum]] == YES）{
randomnum = arc4random（）％[wordToShuffle length];
}

[usedNumberSet addObject：[NSNumber numberWithInt：randomnum]];
[outputstring appendFormat：@％c，[wordToShuffle characterAtIndex：randomnum]];
}

CCLOG（@outputstring is：％@，outputstring）;
return outputstring;

}


仪器给我以下信息：

Leaked Object = NSCFString，Responsible Library = Foundation，Responsible Frame = - [NSPlaceholderMutableString initWithCapacity：]

任何想法？

提前感谢。

解决方案>

你真的不需要使用可变字符串...特别是因为你的返回类型是NSString。只要使用stringByAppendingFormat：

   - （NSString *）randomizeHint：（NSString *）wordToShuffle {
 
 NSString * outputstring = @; 
 
 NSMutableSet * usedNumberSet = [NSMutableSet setWithCapacity：[wordToShuffle length]]; 
 
 for（int i = 0; i <[wordToShuffle length]; i ++）{
 int randomnum = arc4random（）％[wordToShuffle length]; 
 
 while（[usedNumberSet containsObject：[NSNumber numberWithInt：randomnum]] == YES）{
 randomnum = arc4random（）％[wordToShuffle length]; 
} 
 
 [usedNumberSet addObject：[NSNumber numberWithInt：randomnum]]; 
 
 //只是设置outputstring这样...无需担心泄漏的可变字符串然后
 outputstring = [outputstring stringByAppendingFormat：@％c，
 [wordToShuffle characterAtIndex：randomnum]]; 
} 
 
 
 return outputstring; 
 
} 
  

Have been playing around with instruments with not much luck in figuring out how to solve this memory leak.

Firstly the code:

-(NSString *) randomizeHint:(NSString *) wordToShuffle{

    NSMutableString * outputstring = [NSMutableString stringWithCapacity:[wordToShuffle length]];
    NSMutableSet * usedNumberSet = [NSMutableSet setWithCapacity:[wordToShuffle length]];

    for (int i=0; i<[wordToShuffle length]; i++) {
        int randomnum = arc4random()%[wordToShuffle length];

        while ([usedNumberSet containsObject:[NSNumber numberWithInt:randomnum]]==YES) {
            randomnum = arc4random()%[wordToShuffle length];
        }

        [usedNumberSet addObject:[NSNumber numberWithInt:randomnum]];
        [outputstring appendFormat:@"%c",[wordToShuffle characterAtIndex:randomnum]];
    }

    CCLOG(@"outputstring is:%@",outputstring);
    return outputstring;

 }

Instruments is giving me the following:

Leaked Object = NSCFString, Responsible Library = Foundation, Responsible Frame = -[NSPlaceholderMutableString initWithCapacity:]

Any ideas?

Thanks in advance.

解决方案

You don't really need to use a mutable string... especially since your return type is NSString. Just use stringByAppendingFormat:

-(NSString *) randomizeHint:(NSString *) wordToShuffle{

    NSString * outputstring = @"";

    NSMutableSet * usedNumberSet = [NSMutableSet setWithCapacity:[wordToShuffle length]];

    for (int i=0; i<[wordToShuffle length]; i++) {
        int randomnum = arc4random()%[wordToShuffle length];

        while ([usedNumberSet containsObject:[NSNumber numberWithInt:randomnum]]==YES) {
            randomnum = arc4random()%[wordToShuffle length];
        }

        [usedNumberSet addObject:[NSNumber numberWithInt:randomnum]];

        // just set outputstring like so... no need to worry about a leaky mutable string then
        outputstring = [outputstring stringByAppendingFormat:@"%c",
                    [wordToShuffle characterAtIndex:randomnum]];
    }


    return outputstring;

}

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