Declare public static variable in objective c

Question

I want a static varibale in .h of a class and want it to be inherited to its child class.

@interface :UIViewController
static bool isSearchWindowOpen ; //something like this.
@end

If i write like :

static bool isSearchWindowOpen ; 
@interface :UIViewController
    @end

it works fine but cannot be inherited by child classes.

pls suggest.

What's the colon in the interface declaration? What do you mean by "inherit"? Do you want to make the variable visible or do you want to have each (sub-) class refer to its own variable? It's not clear what you are trying to achieve. — Nikolai Ruhe, Mar 04 '14 at 10:06

score 1 · Answer 1 · answered Mar 04 '14 at 09:27

This sounds a bit like you are confusing this with some other programming language, like C++. In Objective-C, just like C, a static variable is a variable with file scope. If you declare a static variable in a header file, then any source file including that header file has its own copy of the static variable.

You'd probably want a class method

+ (BOOL)isSearchWindowOpen

with implementation

static BOOL sSearchWindowOpen;
+ (void)setSearchWindowOpen:(BOOL)open { sSearchWindowOpen = open; }
+ (BOOL)isSearchWindowOpen { return sSearchWindowOpen; }

Probably even better to write code that checks whether the search window is open, instead of relying on a static variable that you have to track correctly all the time.

score 0 · Accepted Answer · answered Mar 04 '14 at 09:22

The variable as declared has nothing to do with the class. It’s a global static in the “C sense”: only code in the same file can access it. (See Wikipedia for details.) You can write class accessors:

static BOOL foo;

+ (void) setFoo: (BOOL) newFoo
{
    foo = newFoo;
}

That way the class descendants can access the variable, too. But it’s not a good idea anyway. What problem are you trying to solve?

Declare public static variable in objective c

2 Answers2