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 bu
How about a Pair category on NSNumber that uses associated objects, something like the code below (untested, may require iOS4 as I'm not sure when associated objects were introduced).
#import <objc/runtime.h>
@implementation NSNumber(Pair)
#define PAIR_KEY 'p'
- (NSNumber *) pairNumber:(NSNumber *)second
{
char secondKey = PAIR_KEY;
objc_setAssociatedObject(self, &secondKey, second, OBJC_ASSOCIATION_RETAIN);
return self;
}
- (NSNumber *) pairedNumber
{
char secondKey = PAIR_KEY;
NSNumber *associatedObject = (NSNumber *)objc_getAssociatedObject(self, &secondKey);
return associatedObject;
}
@end
You would use it like so:
BOOL myBool = NO;
NSNumber *storedBool = [NSNumber numberWithBool:myBool];
[myOtherNumber pairNumber:storedBool];
And to get it out:
NSNumber *boolNumber = [myOtherNumber pairedNumber];
Using anonymous struct and struct literals, you might be able to do something like
NSValue * v = [NSValue valueWithBytes:(struct {NSInteger i; bool b;}){i,b} objCType:(struct {NSInteger i; bool b;})];
and then to read,
struct {NSInteger i; bool b;} foo;
[v getValue:&foo];
It's a bit cleaner if you name your struct though.
You can write your own data structure object - for such a simple case, it would be pretty easy:
@interface Pair : NSObject
{
NSInteger integer;
BOOL boolean;
}
@property (nonatomic, assign) integer;
@property (nonatomic, assign) boolean;
@end
And a matching implementation, then you stick your Pair
objects into the NSArray
problem free.
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.
You can use the STL in Objective-C++. All you need to do is change the extension of your .m file to .mm and I would also advise you use #import
instead of #include
. That way you can use your pair STL container.