iOS: issues using variables inside MACRO

Question

Can anyone please tell me why following Warns me "unused variable variable str"? SetAccessibilityLabelForView is a MACRO.

NSString *str = [NSString stringWithFormat:dynString, index];
SetAccessibilityLabelForView(myView, str);

dynamicString is setup in singleton class like "dynamic%d".

Macro:

#if RUN_TESTS
#define SetAccessibilityLabelForView(view, label) view.accessibilityLabel = label
#else
#define SetAccessibilityLabelForView(view, label)
#endif

WARNING comes for both the cases when RUN_TESTS true or false but if I removed else part then Warning goes away!

I have tried using following to get rid of warning,

  SetAccessibilityLabelForView(myView, [NSString stringWithFormat:dynString, index])

that gives me ERROR: "Too many arguments provided to function-like macro invocation"!

Then I have changed my macro to following,

#if RUN_TESTS
#define SetAccessibilityLabelForView(view, label, ...) view.accessibilityLabel = label
#else
#define SetAccessibilityLabelForView(view, label, ...)
#endif

Now same line works when RUN_TESTS FALSE but gives error "Expected ']'" when RUN_TESTS is TRUE!! Phew!!

Can someone please help me here. I want to get macro working for both the cases but just want to ignore lines generated by macro when RUN_TESTS is FALSE.

Answer 1

I couldn't resolve this issue! I am ended up ignoring unsused variable warning like below.

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-variable"

NSString *str = [NSString stringWithFormat:dynString, index];
SetAccessibilityLabelForView(myView, str);

#pragma clang diagnostic pop

[EDIT]

Finally I came out with better solution writting another macro to support formatted string..

#if RUN_TESTS
#define SetAccessibilityFormatedLabelForView(view, labelFormat, ...) view.accessibilityLabel = [NSString stringWithFormat:labelFormat, __VA_ARGS__]
#else
#define SetAccessibilityFormatedLabelForView(view, labelFormat, ...)
#endif

Usage:

SetAccessibilityFormatedLabelForView(myView, dynString, index);

Answer 2

The first is going wrong because if RUN_TESTS is not defined, then the code:

NSString *str = [NSString stringWithFormat:dynString, index];
SetAccessibilityLabelForView(myView, str);

gets expanded to:

NSString *str = [NSString stringWithFormat: dynString, index];
-blank-

Try doing this instead (with the first version of the macro):

SetAccessibilityLabelForView(myView, [NSString stringWithFormat: dynString, index]);

This gets expanded to this if RUN_TESTS is defined:

myView.accessibilityLabel = [NSString stringWithFormat: dynString, index];

or just completely compiled out if it isn't (so should build fine in both cases).