Equivalent of C++ STL container "pair<T1, T2>" in Objective-C?

user_151939 0
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I'm new to Objective-C, so please don't judge me too much. I was wondering: Is there an equivalent of the C++ STL pair container I can use in Objective-C?

I want to build an array that contains an NSInteger associated to an NSBool. I know I could use an array with each entry being a NSDictionary with a single key-value but I find it to be a little overkill.

Any ideas?

Thanks.

std-pair objective-c stl iphone c++
5 Answers

Yet another option, is to (ab)use a single-entry NSDictionary for storing the pair - since NSDictionary can now be defined to force typed "key" and "value" and also supports literals as syntactic sugar. The drawback - the pair can only hold NSObjects (instance references) and not primitive values.

A sample would look like this:

typedef NSDictionary<NSString *, NSDate *> *Pair;

And then in your code:

Pair myPair = @{@"my name": [NSDate date]};
Pair myOtherPair =  @{@"his name": [NSDate date]};
NSArray<Pair> *myArrayOfPairs = @[myPair, myOtherPair];

Go on and print the results:

NSLog(@"%@", myArrayOfPairs);

and it looks very much like what you'd expect.

2019-03-18 16:08:21.740667+0200 TesterApp[23135:23269890] (
  {
    "my name" = "2019-03-18 14:08:21 +0000";
  },
  {
    "his name" = "2019-03-18 14:08:21 +0000";
  }
)

Payback time comes as you try to extract values from the so-called "Pair". You have to actually dig that single entry from the NSDictionary, not by its "Key" as usual, but assuming there's only one entry, like this:

Pair somePair = myArrayOfPairs.lastObject;
NSString *name = somePair.allKeys.firstObject;
NSDate *date = somePair.allValues.firstObject;
NSLog(@"name: %@ date: %@", name, date);

which finally yields:

name: his name date: Mon Mar 18 16:16:43 2019

I don't especially recommend this alternative, but it has its niceties and benefits.

user_6092850
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