CODEWITHSUNDEEP
ioscocoa-touchnsarraynsdictionary
dbarrett
dbarrett

Reputation: 219

Adding objects to dictionary in a loop overwrites previous values

I have three NSArrays, and I want to combine them all into a single NSDictionary. The problem is that as I iterate through the arrays and create the dictionary, it overwrites the previous object. In the end I only have one object in my dictionary. What am I doing wrong? Here's my code:

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
for(int i=0; i<[array0 count]; i++) {
    [dict setObject:[array0 objectAtIndex:i] 
             forKey:@"one"];
    [dict setObject:[array1 objectAtIndex:i] f
              orKey:@"two"];
    [dict setObject:[array2 objectAtIndex:i] 
             forKey:@"three"];
}

Maybe this will clarify what I mean... this is the result I'm going for: 

{one = array0_obj0, two = array1_obj0, three = array2_obj0},
{one = array0_obj1, two = array1_obj1, three = array2_obj1},
{one = array0_obj2, two = array1_obj2, three = array2_obj2}, 
etc

Thanks

Upvotes: 3

Views: 2817

Answers (4)

E-Riddie
E-Riddie

Reputation: 14780

Issue

You are inserting and replacing the same object at the specific key. So all what dictionary has is its last object at the last index.

Solution

Use this code to add the three arrays into one dictionary with your specific keys.

NSDictionary *yourDictinary = @{@"one": array0, @"two": array1, @"three": array3};

Edit

If you need to add objects of your NSMutableArrays to one NSDictionary you can follow the answer posted by @ElJay, but that's not a good practice, since you are dealing with multiple objects with unique keys.

Update

To do that thing, we are talking about a single NSMutableArray and multiple NSDictinarys.

Follow this code:

NSMutableArray *allObjects = [NSMutableArray new];
for(int i=0; i<[array0 count]; i++) {
    dict = @{@"one": array0[i], @"two": array1[i], @"three": array2[i]};
    [allObjects addObject:dict];
}

Upvotes: 5

LJ Wilson
LJ Wilson

Reputation: 14427

Here ya go:

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
for(int i=0; i<[array0 count]; i++) {
    [dict setObject:[array0 objectAtIndex:i] forKey:[NSString stringWithFormat:@"arr0_%d", i]];
    [dict setObject:[array1 objectAtIndex:i] forKey:[NSString stringWithFormat:@"arr1_%d", i]];
    [dict setObject:[array2 objectAtIndex:i] forKey:[NSString stringWithFormat:@"arr2_%d", i]];
}

Edit - with revised question:

self.array0 = @[@"Array0_0",@"Array0_1",@"Array0_2", @"Array0_3"];
self.array1 = @[@"Array1_0",@"Array1_1",@"Array1_2", @"Array1_3"];
self.array2 = @[@"Array2_0",@"Array2_1",@"Array2_2", @"Array2_3"];

NSMutableArray *finalArray = [[NSMutableArray alloc] init];

for (int i=0; i< [_array0 count]; i++) {

    NSDictionary *dict = @{@"one":[_array0 objectAtIndex:i], @"two":[_array1 objectAtIndex:i],@"three":[_array2 objectAtIndex:i]};
    [finalArray addObject:dict];
}

NSLog(@"finalArray = %@", [finalArray description]);

Upvotes: 4

android_user77
android_user77

Reputation: 54

If you want many dictionary but only three keys, you should save each dict in an array.

Upvotes: -1

chedabob
chedabob

Reputation: 5881

You're reusing the keys ("one", "two" and "three") through each iteration of the loop. Keys in an NSDictionary have to be unique.

Upvotes: 3

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