NSMutableArray覆盖for循环

我搜索了周围，并认为我找到了答案，但它似乎并没有工作。我正在尝试制作一个字典的数组以供日后排序等。我可以将所有正确的数据写入字典对象和密钥对，但是当我尝试将字典添加到数组时，以前的数组条目会被“覆盖”。我意识到我在指向NSArray的指针上做错了什么，但我无法弄清楚。有一篇文章建议将数组的实例化移出for循环，但以下两个代码片段会产生相同的结果。NSMutableArray覆盖for循环

NSMutableDictionary *tempMatricesNW = [NSMutableDictionary dictionary]; 

NSUInteger middle = 0; 

if (([factorsNW count] % 2) != 0) { 
    middle = (([factorsNW count]+1)/2)-1; 
} 

NSMutableArray *tempMatriceArrayNW = [NSMutableArray array]; 

for (NSUInteger i = 1; i < [factorsNW count]-1; i++) { 

    if (i == middle) { 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"x"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"y"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]-[[factorsNW objectAtIndex:i] intValue]] forKey:@"diff"]; 
     [tempMatriceArrayNW addObject:tempMatricesNW]; 
    } 
    else { 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"x"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:(([factorsNW count]-i)-1)] intValue]] forKey:@"y"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:abs([[factorsNW objectAtIndex:i] intValue] - [[factorsNW objectAtIndex:(([factorsNW count]-i)-1)] intValue])] forKey:@"diff"]; 
     [tempMatriceArrayNW addObject:tempMatricesNW]; 
    } 

    NSLog(@"%@", tempMatriceArrayNW); 

}

我得到相同的结果与此...

NSMutableDictionary *tempMatricesNW = [NSMutableDictionary dictionary]; 

NSUInteger middle = 0; 

if (([factorsNW count] % 2) != 0) { 
    middle = (([factorsNW count]+1)/2)-1; 
} 

for (NSUInteger i = 1; i < [factorsNW count]-1; i++) { 

    NSMutableArray *tempMatriceArrayNW = [NSMutableArray array]; 

    if (i == middle) { 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"x"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"y"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]-[[factorsNW objectAtIndex:i] intValue]] forKey:@"diff"]; 
     [tempMatriceArrayNW addObject:tempMatricesNW]; 
    } 
    else { 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"x"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:(([factorsNW count]-i)-1)] intValue]] forKey:@"y"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:abs([[factorsNW objectAtIndex:i] intValue] - [[factorsNW objectAtIndex:(([factorsNW count]-i)-1)] intValue])] forKey:@"diff"]; 
     [tempMatriceArrayNW addObject:tempMatricesNW]; 
    } 

    NSLog(@"%@", tempMatriceArrayNW); 

}

这似乎并不重要，我把NSMutableArray中的实例，所以我必须做一些别的错误...

在此先感谢您的帮助！

来源

2014-03-06 Rory O' Hare

实例化一个新的'NSDictionary'在每个循环 – Volker

太棒了！这很有用，非常感谢。它甚至是完美的。 –

@ SonGoku68的答案似乎显示相同的解决方案，你可能会考虑接受它，所以其他用户看到这个问题有一个有用的答案。 – Volker

您之前的条目将被覆盖，因为您正在使用相同的字典，因此您指向相同的内存分配。您需要创建一个新的字典在你的每一个环路或者添加您tempMatricesNW字典阵列后，再对其进行实例化

NSUInteger middle = 0; 

if (([factorsNW count] % 2) != 0) { 
    middle = (([factorsNW count]+1)/2)-1; 
} 

NSMutableArray *tempMatriceArrayNW = [NSMutableArray array]; 

for (NSUInteger i = 1; i < [factorsNW count]-1; i++) { 

    NSMutableDictionary *tempMatricesNW = [NSMutableDictionary dictionary]; 

    if (i == middle) { 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"x"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"y"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]-[[factorsNW objectAtIndex:i] intValue]] forKey:@"diff"]; 
     [tempMatriceArrayNW addObject:tempMatricesNW]; 
    } 
    else { 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:i] intValue]] forKey:@"x"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:[[factorsNW objectAtIndex:(([factorsNW count]-i)-1)] intValue]] forKey:@"y"]; 
     [tempMatricesNW setObject:[NSNumber numberWithInt:abs([[factorsNW objectAtIndex:i] intValue] - [[factorsNW objectAtIndex:(([factorsNW count]-i)-1)] intValue])] forKey:@"diff"]; 
     [tempMatriceArrayNW addObject:tempMatricesNW]; 
    } 

    NSLog(@"%@", tempMatriceArrayNW); 

}

来源

2014-03-06 10:11:59

NSMutableArray覆盖for循环

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