NSMutableArray覆蓋for循環

我搜索了周圍，並認爲我找到了答案，但它似乎並沒有工作。我正在嘗試製作一個字典的數組以供日後排序等。我可以將所有正確的數據寫入字典對象和密鑰對，但是當我嘗試將字典添加到數組時，以前的數組條目會被「覆蓋」。我意識到我在指向NSArray的指針上做錯了什麼，但我無法弄清楚。有一篇文章建議將數組的實例化移出for循環，但以下兩個代碼片段會產生相同的結果。NSMutableArray覆蓋for循環

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); 

}

我得到相同的結果與此...

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); 

}

這似乎並不重要，我把NSMutableArray中的實例，所以我必須做一些別的錯誤...

在此先感謝您的幫助！

來源

2014-03-06 Rory O' Hare

實例化一個新的'NSDictionary'在每個循環 – Volker

太棒了！這很有用，非常感謝。它甚至是完美的。 –

@ SonGoku68的答案似乎顯示相同的解決方案，你可能會考慮接受它，所以其他用戶看到這個問題有一個有用的答案。 – Volker

您之前的條目將被覆蓋，因爲您正在使用相同的字典，因此您指向相同的內存分配。您需要創建一個新的字典在你的每一個環路或者添加您tempMatricesNW字典陣列後，再對其進行實例化

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); 

}

來源

2014-03-06 10:11:59

NSMutableArray覆蓋for循環

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