NSMutableArray insert object at last index

Question

I am trying to copy the objects content of a NSDictionary to a NSMutableArray, and I am using the following code :

             // Use when fetching binary data
             NSData *responseData = [request responseData];

             // View the data returned - should be ready for parsing.
             resultsDictionary = [responseData objectFromJSONData];
             NSLog(@"ResultsDictionary:%@", resultsDictionary);

             self.OnlineObjects = [[[NSMutableArray alloc] init] autorelease];

             for (NSDictionary * dataDict in resultsDictionary) {
                 [OnlineObjects insertObject:dataDict atIndex:0];
             }

             NSLog(@"OnlineObjects:%@", OnlineObjects);

This is working as i am getting all objects from the Dictionary, but the objects order have been revers, first object is now last ...

How can tell the insertObject to add the object at the last index ?

Thanks

Alexander · Accepted Answer · 2012-08-31 14:18:05Z

2

You can use the addObject: method instead.

To get rid of the hash order problem get allKeys, sort the array and then use the elements as keys to get the objects in proper order.

Verbose example (for integer keys):

NSArray *indices = [[resultsDictionary allKeys] sortedArrayUsingComparator:^(id obj1, id obj2) {
    if ( [obj1 intValue] > [obj2 intValue] ) {
        return (NSComparisonResult)NSOrderedDescending;
    }
    if ( [obj1 intValue] < [obj2 intValue] ) {
        return (NSComparisonResult)NSOrderedAscending;
    }
    return (NSComparisonResult)NSOrderedSame;
}];

for (int i = 0; i < [indices count]; i++) {
    NSDictionary *obj = [resultsDictionary objectForKey:[indices objectAtIndex:i]];
    [OnlineObjects addObject:obj];
}

edited Aug 31, 2012 at 14:18

answered Aug 31, 2012 at 14:13

Alexander

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4 Comments

Ben Over a year ago

Looks good but when trying your code I am getting the following error -[JKArray allKeys]: unrecognized selector sent to instance 0x2e3c60

Alexander Over a year ago

Then the object you are receiving is already an array of some sort.

Alexander Over a year ago

Use the for (NSDictionary * dataDict in resultsDictionary) part from your code, but replace insertObject:atIndex: with addObject:

Ben Over a year ago

That fixed my issue, can´t believe I didn´t try this before. Many thanks alexander !

Asciiom · Accepted Answer · 2012-08-31 14:08:18Z

0

The order of the elements in a NSDictionary is undefined, you don't know in which order they will be retrieved from the dictionary. The only way to do have the array sorted is to sort it once all the values from the dictionary are transferred to the array.

answered Aug 31, 2012 at 14:08

Asciiom

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Comments

Angel G. Olloqui · Accepted Answer · 2012-08-31 14:11:35Z

0

Two things you should know:

NSDictionary is a key-value container, which does not guarantee the order of the objects. You have no way to ensure that the order of inserting will be mantained when reading by using this data structure. Check other strategies if order is important for you, but do not rely on NSDictionary for this.
You have a couple of methods to extract the info of the keys and data: allKeys and allValues. Use them instead of creating your own.

answered Aug 31, 2012 at 14:11

Angel G. Olloqui

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