Stringify macro values in Objective C?

Question

I'm developing in XCode 4.2, and was wondering how I could stringify macro parameters? I was trying to use # as I thought I would do in C, but to no avail. Here is my macro:

#define ASSIGN_PROPERTY(PROP_NAME, PROP_NAME_PARAM) { \
  if (PROP_NAME_PARAM == nil) { \
    NSAssert(PROP_NAME != nil, @"#PROP_NAME is already nil"); \
    PROP_NAME = nil; \
  } else { \
    NSAssert1(PROP_NAME == nil, @"#PROP_NAME is already set, address=%p", PROP_NAME); \
    PROP_NAME = PROP_NAME_PARAM; \
  } \
}

Then in a class that has foo as a property, I define its setter like so:

- (void) setFoo:(NSObject *)fooParam {
  ASSIGN_PROPERTY(foo, fooParam)
}

Say a client calls setFoo with a non-nil value, but the foo property is already non-nil. I want the macro to print:

foo is already set, address=0x5e55400

But instead it's printing:

#PROP_NAME is already set, address=0x5e55400

Any advice?

possible duplicate of How to make a macro that can take a string? — bobbymcr
– bobbymcr, Commented Dec 6, 2011 at 2:24
@bryanmac I want to assert if I attempt to assign a non-nil value while foo is already non-nil, or assign a nil value while foo is already nil. Using @property(assign) will just blindly overwrite the value in either case. — shadowmatter
– shadowmatter, Commented Dec 6, 2011 at 2:38

Lily Ballard · Accepted Answer · 2011-12-06 02:23:46Z

2

Have you tried something like

NSAssert(PROP_NAME != nil, @"%s is already nil", #PROP_NAME);

answered Dec 6, 2011 at 2:23

Lily Ballard

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