CODEWITHSUNDEEP
iphoneobjective-ciosmacrosconditional-compilation
Lolloz89
Lolloz89

Reputation: 2809

ifdef syntax doesn't work

I want dynamically define a constant based on the different device heights. I tried to use this code but it doesn't work:

#define isPhone568 ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone && [UIScreen mainScreen].bounds.size.height == 568)

#ifdef isPhone568
    #define kColumnHeightPortrait568 548
#else
    #define kColumnHeightPortrait568 (IS_IPAD ? 984 : 460)
#endif

Even if i'm using the 3.5" simulator, i get 548. What's wrong with this?

Upvotes: 1

Views: 167

Answers (2)

Yuan Xulei
Yuan Xulei

Reputation: 11

The #ifdef is used to check whether a macro is defined. As you define isPhone568 in the first line, #ifdef isPhone568 will be true.

If you want to test the value of an expression rather than the existance of a macro, you should use #if instead. But #if can test no more than the simple arithmetic expression, just as paxdiablo mentioned, "You can't run code in macro definitions".

Upvotes: 1

paxdiablo
paxdiablo

Reputation: 881983

You can't run code in macro definitions, it's a simple text substitution process that happens at compile-time. Hence you have no idea what the device characteristics are at that point, because you're not on the target device.

If you want to use something like [UIDevice currentDevice] userInterfaceIdiom, you have to evaluate it at run-time, not in a compile-time macro, something like:

int kColumnHeightPortrait568 = 548;
if (([[UIDevice currentDevice] userInterfaceIdiom] != UIUserInterfaceIdiomPhone)
   || ([UIScreen mainScreen].bounds.size.height != 568))
{
    kColumnHeightPortrait568 = (IS_IPAD ? 984 : 460);
}

Upvotes: 2

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