編輯和刪除NSMutable數組中的元素

Question

我有一個NSMutableArray，其數據為字典格式，例如：

(
        {
        subject = “Maths";
        rollNo = "#1";
        division = A;
    },
        {
        subject = “Science”;
        rollNo = “#2”;
        division = A;
    },
 {
        subject = “Maths";
        rollNo = “#3”;
        division = A;
    },
 {
        subject = “Maths";
        rollNo = “#4”;
        division = B;
    },
 {
        subject = “Science”;
        rollNo = “#5”;
        division = A;
    },
 {
        subject = “English”;
        rollNo = “#6”;
        division = A;
    },
)

現在，我需要合並屬於同一主題和部門的卷號，並修改現有的數組，如下所示

(
        {
        subject = “Maths";
        rollNo = “#1,#3”;
        division = A;
    },
        {
        subject = “Science”;
        rollNo = “#2,#5”;
        division = A;
    },

 {
        subject = “Maths";
        rollNo = “#4”;
        division = B;
    },

 {
        subject = “English”;
        rollNo = “#6”;
        division = A;
    },
)

This is how I'm trying to achieve it

 NSMutableArray *temp =[studentDetailsArray mutableCopy];
 NSMutableArray *elementToDelete = [NSMutableArray array];
 for (int m=0; m<temp.count-1; m++)
 {
 if ([temp[m][@"subject"] isEqualToString:temp[m+1][@"subject"]] && [temp[m][@“division”] isEqualToString:temp[m+1][@“division”]])
 {
 [temp[m] replaceObjectAtIndex:1 withObject:@{@"rollNo":[NSString stringWithFormat:@"%@, %@",temp[m][@"rollNo"],temp[m+1][@"rollNo"]]}];
 //                    [temp[m] setValue:[NSString stringWithFormat:@"%@, %@",temp[m][@"rollNo"],temp[m+1][@"rollNo"]]forKey:@"rollNo"];
 [elementToDelete addObject:temp[m+1]];
 }
 }

 [temp removeObjectsInArray:elementToDelete]; 

但是我在替換對象時遇到錯誤，因此是否必須將其轉換為NSMutableDictionary？ 我應該如何以一種簡單的方式進行此操作？

Answer 1

不需要創建更多的數組。 您收到錯誤，因為此行：

[temp[m] replaceObjectAtIndex:1 withObject:@{@"rollNo":[NSString stringWithFormat:@"%@, %@",temp[m][@"rollNo"],temp[m+1][@"rollNo"]]}];

它應該是

NSMutableDictionary *mutable = [temp[m] mutableCopy];

[mutable setObject:[NSString stringWithFormat:@"%@, %@",temp[m][@"rollNo"],temp[m+1][@"rollNo"]] forKey:@"rollNo"];
[temp replaceObjectAtIndex:m withObject:mutable];