CODEWITHSUNDEEP
objective-c
brianSan
brianSan

Reputation: 535

How do you call a global variable within implementation files in Objective-C

Lets say I want a BOOL to indicate the status of something. Then I call a class method that uses a recursive function to construct a certain string. Is there anyway to keep this BOOL outside of the class method so that it's status can change outside of the recursion? I'm finding a hard to ask this question clearly but I'm hoping you guys know what I'm trying to ask :/

Upvotes: 2

Views: 177

Answers (2)

justin
justin

Reputation: 104698

There are two primitive approaches:

1) Visible to multiple files:

MONGlobalBOOL.h

extern BOOL MONGlobalBOOL;

MONGlobalBOOL.m

BOOL MONGlobalBOOL = NO;

2) Visible to one file:

MONGlobalBOOL.m

static BOOL MONGlobalBOOL = NO;

You don't want this in your headers because that will just emit a copy of the variable for each translation.

In use:

+ (void)method
{
  if (MONGlobalBOOL) {
    ...
  }
}

Careful, global mutable data frequently decays to evil stuff. You can likely solve your exact problem by creating a local variable on the stack.

Upvotes: 2

Jay Wardell
Jay Wardell

Reputation: 2290

As far as language support goes, anything that can be done in C can be done in Objective C. So you probably just want to use a static variable:

static BOOL globalFlag

Of course, if you only want to reference the variable within the recursive method, as in you want to send a flag to a calling method from a deeper recursion of the method, then you may do better passing the variable by reference:

- (void)someMethodWithRecursionFlag:(BOOL *)recursionFlag;

and then setting it by reference when needed:

*recursionFlag = YES;

and reading it when you're interested in it:

[self someMethodWithRecursionFlag:recursionFlag];
if (*recursionFlag)
    [self doSomethingInteresting];

Upvotes: 1

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