Add array into another array

Question

How do I add one array into another one? The problem is that I insert this array several times in different "slots", but the array I insert changes, so I get a array with every field looking the same.

Is there an option to get the content of array 1 and put the whole content into one field of array 2?

I think the problem is that the array is somehow looking like this :

NSMutableArray *bigArray = [

0: dynamicArray

1: dynamicArray

2: dynamicArray

3: dynamicArray

]

instead of:

NSMutableArray *bigArray = [

0: contentOfDynamicArray

1: contentOfDynamicArray

2: contentOfDynamicArray

3: contentOfDynamicArray

]

My code:

    twoDArray = [[NSMutableArray alloc] init];
    cat1 = [[NSMutableArray alloc] init];

    for (int k = 0; k < [noDuplicatesCat count]; k++) {
        NSLog(@"cat1: %@", cat1);
        [cat1 removeAllObjects];
        for (int i = 0; i < [parseJSONArray count]; i++) {
            NSMutableArray *temp;
            [temp removeAllObjects];
            temp = [[NSMutableArray alloc] init];
            temp = [parseJSONArray objectAtIndex:i];

            if ([[temp valueForKey:@"category"] isEqual:[noDuplicatesCat objectAtIndex:k]]){
                NSLog(@"equal");
                [cat1 addObject:temp];
            } else {
                NSLog(@"not equal");
            }
        }
        [twoDArray addObject:cat1];
        NSLog(@"2dArray: %@", twoDArray);
    }

When you insert an object into an array, you insert a POINTER to the object. If you subsequently modify the object and insert again, you will simply have the SAME object inserted twice. If you want DIFFERENT objects you must CREATE different objects. — Hot Licks
– Hot Licks, Commented Feb 12, 2014 at 23:37
(And in the above code doing temp = [[NSMutableArray alloc] init]; does not really create a new object, since you write a new value to temp in the very next line, wiping out the new array.) — Hot Licks
– Hot Licks, Commented Feb 12, 2014 at 23:39
(And you appear to be inserting the same cat1 object into twoDArray again and again.) — Hot Licks
– Hot Licks, Commented Feb 12, 2014 at 23:40
Thank you for your comment. I found a way to not create another object: [bigarray addObject:[NSMutableArray arrayWithArray:smallaray]]; — seniorbenelli
– seniorbenelli, Commented Feb 13, 2014 at 8:02
I hate to disappoint you, but arrayWithArray does create another object. — Hot Licks
– Hot Licks, Commented Feb 13, 2014 at 12:09

Wil Shipley · Accepted Answer · 2014-02-13 07:56:57Z

1

- (void)replaceObjectsInRange:(NSRange)range withObjectsFromArray:(NSArray *)otherArray;

Also, your code is kinda nuts. Don’t use ‘i’ and ‘k’ as variable names, actually describe what kind of index you have. And this:

        NSMutableArray *temp;
        [temp removeAllObjects];
        temp = [[NSMutableArray alloc] init];
        temp = [parseJSONArray objectAtIndex:i];

Makes no sense. The second line removes all objects from an UNinitialized variable, which does nothing. The third creates it, which is fine, but then the fourth overwrites the thing you just created.

edited Feb 13, 2014 at 7:56

answered Feb 12, 2014 at 23:39

Wil Shipley

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3 Comments

Clay Bridges Over a year ago

"...from an initialized...": I'm guessing you meant "uninitialized". Good comment.

seniorbenelli Over a year ago

thanks for comment, i know my code isn't very nice and i try to optimize it. I found a easy solution : [bigarray addObject:[NSMutableArray arrayWithArray:smallaray]];

Wil Shipley Over a year ago

Well, everyone starts somewhere. My code was pretty strange 30 years ago. Just keep at it, no shame in that.

user3125367 · Accepted Answer · 2014-02-13 08:33:49Z

0

It seems like you are trying to split big record array parseJSONArray by record's category field according to [unique] categories from noDuplicatesCat. The resulting twoDArray has the same order as noDuplicatesCat.

Here is the reduced version:

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

for (id category in noDuplicatesCat) {
    NSMutableArray *cat1 = [[NSMutableArray alloc] init];
    [twoDArray addObject:cat1];

    for (id item in parseJSONArray)
        if ([[item valueForKey:@"category"] isEqual:category])
            [cat1 addObject:item];
}

answered Feb 13, 2014 at 8:33

user3125367

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Comments

seniorbenelli · Accepted Answer · 2014-02-13 08:03:16Z

0

Thank you, I just found a possible solution: [bigarray addObject:[NSMutableArray arrayWithArray:smallaray]];

answered Feb 13, 2014 at 8:03

seniorbenelli

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1 Comment

Clay Bridges Over a year ago

Hmmm. Does the array added to bigarray need to be mutable? Does it need to be a copy of smallarray? (BTW, you are better off using camel-case consistently, e.g. bigArray, smallArray.

Clay Bridges · Accepted Answer · 2014-02-13 12:45:26Z

There's a lot wrong with your code, but I don't want to harsh on you. Kudos to you for jumping in and trying to learn something, and also for putting your code out there. I'm going to try to rewrite what you've done based on my very limited understanding of what your are trying to do.

First, some clues:

 temp = [parseJSONArray objectAtIndex:i]
 // and
 if ([[temp valueForKey:@"category"] ...

lead me to believe that parseJSONArray is an array of NSDictionarys. You probably should use -[NSDictionary objectForKey:], e.g.

NSDictionary *temp = [parseJSONArray objectAtIndex:i]
 // and
 if ([[temp objectForKey:@"category"] ...

I'd also bet that [temp objectForKey:@"category"] will return an NSString.

If these assumptions are correct, this looks kind of like what you are trying to do:

// NSArray *noDuplicatesCat = <array of strings>
NSMutableArray *arrayOfArrayOfJSONDicts = [NSMutableArray array];

for (NSString *cat in noDuplicatesCat) {
    NSMutableArray *gather = [NSMutableArray array];  
    for (NSDictionary *jsonDict in parseJSONArray) {
        if ([jsonDict objectForKey:@"category"] isEqualToString:cat]) {
            [gather addObject:jsonDict];
        }
    }
    [arrayOfArrayOfJSONDicts addObject:gather]
}

I'm not sure what useful purpose that is serving. It might be useful or interesting if you told us, at a higher level, what you were trying to accomplish. Prevent duplicates somehow? You can edit your question to add an addendum.

Regardless, given what I'm seeing right now, you really need to hit the books to avoid programming yourself into a complete mess right now. I'd recommend playing around a lot with NSArrays and NSDictionarys until you really understand what you are doing. Good luck!

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