On Jun 5, 2015, at 10:02 PM, Carl Hoefs <[email protected]> wrote:
> If I use CFSTR() in the following way:
> CFStringRef mystr = CFSTR( "This is a string" );
> there is no problem.
>
> However, if I use a variable instead of “string” Xcode flags this as an error:
> const char *mystring = "This is a string";
> CFStringRef mystr = CFSTR( mystring );
> ^ <— Expected ")"
>
> In CFString.h, CFSTR is defined as:
> #define CFSTR(cStr) __CFStringMakeConstantString("" cStr "")
>
> Is it possible to use CFSTR() with a const char * variable?
No. As you can see from the quoted macro definition, it relies on
concatenation of adjacent string literals.
You should use an appropriate CFStringCreate…() function to create a CFString
from the C string. Or just create a CFString or NSString literal from the
start.
Be careful with CFStringCreateWithCStringNoCopy(…, kCFAllocatorNull), which you
might be tempted to use. Only use that with pointer to static storage. The
mystring variable in your example does point to static storage, but could be
changed to point to something else (it's a pointer to const char, not a const
pointer to const char).
Something like this is _not_ safe:
const char mystring[] = "This is a string";
That is auto-lifetime storage allocated on the heap, which will be deallocated
at end of scope.
This would be safe:
static const char mystring[] = "This is a string";
Regards,
Ken
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