Objective C array "key" instead of index

Question

I want to be able to use NSString, or something similar to store an array of strings, but access them by a key (I think this is what it's called), instead of a numeric index.

For example, instead of doing this:

return names[3];

Do something like this:

return names["Bob"];

How do you store and retrieve values like this?

Please excuse my lack of knowledge of this. I've been working with Objective C for about a year now, but never had to do anything like this.

Tim Dean · Accepted Answer · 2011-09-14 16:20:18Z

6

In Objective-C, you do this with the NSDictionary class and its mutable subclass NSMutableDictionary. You can get the value for a key using

NSString *value = [myDictionary objectForKey:@"Bob"];

edited Sep 14, 2011 at 16:20

user557219

answered Sep 14, 2011 at 16:07

Tim Dean

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Stephen Darlington · Accepted Answer · 2011-09-14 16:06:48Z

2

NSDictionary

answered Sep 14, 2011 at 16:06

Stephen Darlington

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James Webster · Accepted Answer · 2011-09-14 16:07:47Z

1

Those kind of arrays are taken from C (of which Objective-C is a superset) which only allow integers as their indices.

You may wish to use NSDictionary and it's objectWithKey style messages.

answered Sep 14, 2011 at 16:07

James Webster

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3 Comments

bbum Over a year ago

Arrays inherently are always by index.... name an array in a language that ultimately isn't? (Out of curiosity)

James Webster Over a year ago

@bbum My knowledge of php is limited.. but php?

bbum Over a year ago

"An array in PHP is actually an ordered map." i.e. it is a dictionary with a determinate key order. That is called an array is, frankly, odd. Without exhaustive research, it appears to be more akin to Ruby's Hashes in that the elements are ordered by order of insertion, but it is still a true map/dictionary behind the scenes.

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