Assignment Makes Pointer from Integer Without a Cast

Question

I have an Obj-C method similar to this:

-(void)getUserDefaults:(BOOL *)refreshDefaults
{
    PostAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

    if (refreshDefaults) {
        [appDelegate retrieveDefaults];
    }
}

When I call it like this I get no warning:

[self getUserDefaults:NO];

When I call it like this I get a warning:

[self getUserDefaults:YES];

warning: passing argument 1 of 'getUserDefaults:' makes pointer from integer without a cast

NOTE: I always call the method passing NO first, then sometime later I pass YES

Can anyone fill me in on what the issue is here? Thanks.

Answer 1

BOOL is a primitive type, not a class, so your method declaration should be

-(void)getUserDefaults:(BOOL)refreshDefaults;

instead. The reason you're getting the warning you are is that 0 (which is what NO is defined to be) is a valid pointer value without a cast, equivalent to NULL, but 1 (which is what YES is defined to be) isn't a valid pointer value without a cast.

Answer 2

getUserDefaults takes a BOOL*. You don't get a warning when you pass NO because NO is 0 and 0 is NULL, which is a legal BOOL*. YES is 1 and the same conversion isn't automatically safe.

You should make getUserDefaults take a plain BOOL, instead of a pointer.

Answer 3

I have never seen Obj-C code before, but I'm pretty sure it's because the 'refreshDefaults' is a pointer to BOOL whereas it should be a BOOL.

I don't know about the typing rules in Obj-C, but it looks like NO is defined as 0 and the compiler has no problems converting that to a pointer value (a NULL pointer.) That would not be the case with integer '1'. (Also note "if (refreshDefaults)" is valid code that checks the pointer refreshDefaults against the NULL pointer)

Answer 4

Cool thanks! That makes sense, and fixed it! Here is the updated code for reference:

-(void)getUserDefaults:(BOOL)refreshDefaults
{
PostAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

if (refreshDefaults) {
    [appDelegate retrieveDefaults];
}
}

Answer 5

In the first case, NO probably defaults to 0 - the null pointer. This is a valid Bool*. Yes will default to 1, and so when it is cast to a Bool* you are passing the integer 1 in - which is then turned into a Bool*.