Objective C - Safely create a static Boolean?

Question

I want to have a static boolean like in Java. This boolean only created once for the entire class, no matter how many instance it has.

I read some posts here. Some of them are suggesting that in .m file, init this variable like

static BOOL myBool = NO;

and then have a getter and a setter function. But I was told that this is not safe and clean in Objective C. A safer and cleaner way to do this is init static variable in function. But if I init it in a function, like

+(Bool)getMyBool {
    static BOOL myBool = NO;
    return myBool;
}

In this way myBool will always NO. What if I want to set this boolean afterwards? If I call static BOOL myBool again, would it give me the same boolean?

"In this way myBool will always NO." – you seem to have missed the point of static. — The Paramagnetic Croissant
– The Paramagnetic Croissant, Commented Jul 10, 2015 at 16:04
The original code is absolutely fine. Whoever told you it's not safe and clean suffers from some object-oriented illness. — gnasher729
– gnasher729, Commented Jul 10, 2015 at 19:04

Community · Accepted Answer · 2017-05-23 11:51:12Z

2

There is nothing inherently “not safe and clean” about a global static variable in Objective-C and they are commonly used when appropriate - they are effectively Objective-C's class variables.

See Setting Static Variables in Objective-C for one way to write the getter and setter functions you mention.

edited May 23, 2017 at 11:51

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answered Jul 10, 2015 at 17:46

CRD

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Comments

katie · Accepted Answer · 2015-07-10 18:59:47Z

0

Try this

+(BOOL)resetBoolOrGet:(BOOL)reset newVal:(BOOL)newValue {
    static BOOL myBool = NO;
    if (reset) {
        myBool = newValue;
    }
    return myBool;
}

So, if you want to assign a new value to this boolean, call

[MyClass resetBoolOrGet:YES newVal:newValue];

If you only wants to get the value of that static boolean, call

[MyClass resetBoolOrGet:NO newVal:(either YES or NO)];

edited Jul 10, 2015 at 18:59

answered Jul 10, 2015 at 16:13

katie

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2 Comments

The Paramagnetic Croissant Over a year ago

bool is a typename in C and C++, don't use it as a variable name.

bbum Over a year ago

That'll work, but I don't see the point of it all unless you really want access to that BOOL from outside the compilation unit.

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