Accessing array/set of objects with keys

Question

I want to be able to add objects to an NSArray and access them with Keys. Currently the way im doing it is creating a seperate NSDictionary of key-value pairs where the value is an integer number representing the index in my NSArray. This seems like an extra step to me.

If my understanding of NSDictionary is correct, only 'values' can be stored: a pointer to an object cannot.

Surely there must be an equivalent NSDictionary type function that allows objects to be stored and accessed with a key? I have looked through the documentation, but cant seem to find any answers, unless im missing something obvious.

So it turns out that actually objects can be used. The problem I was having with objects when I tried before was when I tried to retrieve the object and add it directly as a subview to a view. No object was added to the view... Will have a look at my code again tonight. — GWed
– GWed, Commented Feb 1, 2012 at 13:14
Ah, feeling pretty silly now. There was an error in my code, I was passing nil to the dictionary object that I thought should have been a UIView. To confirm, objects can be used - embarrassed — GWed
– GWed, Commented Feb 1, 2012 at 19:45

Vignesh · Accepted Answer · 2012-02-01 10:05:16Z

1

NSDictionary is to store key value pairs. if you are adding key value pair after you created the dictioanry, use NSMutableDictionary class . example,

[dictionaryObject setObject:@"" forKey:@"abc"];

answered Feb 1, 2012 at 10:05

Vignesh

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DShah · Accepted Answer · 2012-02-01 10:05:22Z

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You can store objects in NSDictionary and can be accessed via keys...

answered Feb 1, 2012 at 10:05

DShah

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score 1 · Accepted Answer · 2012-02-01 10:18:28Z

1

In short, no.

An array (NSArray) is an ordered collection of references to objects, so simply said, an ordered collection of objects.
As opposed to dictionaries, which are unordered and values are accessed by keys.

You understanding of collections is probably wrong, you don't store values, but pointers (references).

The extra step is necessary if you need to store the references in an array, but in this case, you should consider using a dictionary. An option is to use keys that take care of the order.
For example :

[myDictionary objectForKey:@"1"];

could be an equivalent of :

[myArray objectAtIndex:1];

edited Feb 1, 2012 at 10:18

answered Feb 1, 2012 at 10:05

user971401

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wattson12 · Accepted Answer · 2012-02-01 10:03:19Z

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Thats wrong, you can store objects in a NSDictionary. Look at the method dictionaryWithObjects:forKeys: or dictionaryWithObjectsAndKeys:

answered Feb 1, 2012 at 10:03

wattson12

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3 Comments

GWed Over a year ago

Yeah I looked at them. But they didnt work (unless I was doing something silly). I was trying to add UIView object to the dictionary. Will try again...

wattson12 Over a year ago

if you post the code and the error it might help. You can definitely add objects with those methods

GWed Over a year ago

Im not at my developer mac atm. One of the answers above made me think that maybe its the mutable/immutable thing thats messing me up. Will have another look tonight.

dresende · Accepted Answer · 2012-02-01 10:07:12Z

0

I have no experience in Cocoa but looking at the documentation it seems like NSDictionary (or at least NSMutableDictionary) should handle your request (without you using NSArray).

answered Feb 1, 2012 at 10:07

dresende

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Gilles 'SO- stop being evil' · Accepted Answer · 2012-02-01 13:21:26Z

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I think I understand your problem. My suggestion for you is to use NSMutableArray and macros, like:

NSMutableArray *array=[[NSMutableArray alloc]init];
#define SOME_MACRO 0
    id someObject;
    [array insertObject:someObject atIndex:SOME_MACRO];
    id getterObject=[array objectAtIndex:SOME_MACRO];

Of course define the macros in the header file.

edited Feb 1, 2012 at 13:21

Gilles 'SO- stop being evil'

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answered Feb 1, 2012 at 12:36

Applicasa iOS developer

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1 Comment

Gilles 'SO- stop being evil' Over a year ago

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