CODEWITHSUNDEEP
objective-ccocoaboolean
Kenny Winker
Kenny Winker

Reputation: 12107

Best way to implement a true/false/undefined trichotomy variable in objective-c

I'm temped to use an int, and make 0 == NO, 1 == YES, and anything else == undefined. Obviously there are a million ways to do something like this, but what seems like the best way to you? Concerns I can think of include simplicity and memory footprint (e.g. what if I have a lot of these?).

Another way is to use two BOOLs, one for isDefined, and one for value

Another way,

typedef enum { CPStatusUndefined, CPStatusAvailable, CPStatusUnavailable } CPStatus;

Edit, the use case is:

I have a yes/no property that is difficult to calculate. When it is being checked, it is checked frequently (by UIMenuController, OFTEN), but unless the user selects it, it is never checked. The way I chose to deal with this is a tri-type variable. The first time you check, if it is undefined you calculate the yes/no value and return it, after that you just return the yes/no value.

Upvotes: 2

Views: 1110

Answers (3)

Dexter
Dexter

Reputation: 5736

If you want to conserve the most amount of memory, use a char.

char == 0, false char == 1, true else, undefined.

Obviously, you'll want to initialize it at something like -1.

This is the way obj-c does comparator return values: if 0, they are equal. if positive, a > b if negative, a < b

Same idea as above.

Upvotes: 0

Lee
Lee

Reputation: 13542

Use an enum. In Objective-C they work just like they do in C/C++

typedef enum {
  No = 0,
  Yes,
  Other
} tri_type;

tri_type myVar = No;

if( myVar == Yes || myVar == Other ) {
  // whatever
}

Upvotes: 6

d11wtq
d11wtq

Reputation: 35318

How about NSNumber, since it can be nil?

[number boolValue] == YES;
[number boolValue] == NO;
[number boolValue] == nil; // or just number == nil

Upvotes: 1

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