Declaring and using a C function in Objective C

Question

This must be very simple, but I can't figure out how to do this: I have a C-function to monitor current memory usage:

natural_t report_memory(void) {
    struct task_basic_info info;
    mach_msg_type_number_t size = sizeof(info);
    kern_return_t kerr = task_info(mach_task_self(),
                               TASK_BASIC_INFO,
                               (task_info_t)&info,
                               &size);
    if( kerr == KERN_SUCCESS ) {
        return info.resident_size;
    } else {
        NSLog(@"Error with task_info(): %s", mach_error_string(kerr));
        return 0;
    }
}

Now, I would like to use it. How do I declare it in the .h? I tried the (for me) obvious within the objective c methods:

natural_t report_memory(void);

Calling this somewhere in the code:

NSLog(@"Memory used: %u", rvC.report_memory());

The Compiler complains error: called object is not a function. Thus, I assume, the declaration is somehow wrong. I tried several options, but the best I could get was a runtime error... How to fix this?

I probably would want to have an instance method? Or is it possible to use the code from a class method? — Axel
– Axel, Commented Jan 21, 2011 at 17:26
Since the function has no relation whatsoever to view controllers, I would keep it as a C function (declared in a separate header file, defined in a separate implementation file). You can use it from instance or class methods. — user557219
– user557219, Commented Jan 21, 2011 at 17:32

user557219 · Accepted Answer · 2011-01-21 17:17:35Z

10

rvC.report_memory()

should be replaced with

report_memory()

since it is a C function.

answered Jan 21, 2011 at 17:17

user557219

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2 Comments

Axel Over a year ago

but I want to use it from different classes

user557219 Over a year ago

@angrest C functions are independent of classes. Simply call report_memory() wherever you need it.

Martin Babacaev · Accepted Answer · 2011-01-21 17:44:37Z

2

If you want to use this function in other modules, you should also put in your header (.h) file this line

extern natural_t report_memory(void);

answered Jan 21, 2011 at 17:44

Martin Babacaev

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