Re: Can I call Obj-C from a C++ source?

Steve555:

My project is Objective-C++, but from one of the C++ classes I want to
write to the log window:

long val = 123;
NSString nsStr = [NSString stringWithFormat:@"%d", val];
NSLog(nsStr);

That's a very bad habit. The correct code is:
NSLog(@"%d", val);

In your case there's no practical difference, but if nsStr had a %@ and took a
string, it might end up with a % sequence in it, and then NSLog() would print
bad data or crash. If the string being substituted in was user input, you'd be
vulnerable to a format string attack.

That said, if you want to use NSLog from C or C++ code, and have a real reason
not to turn it into an Objective-C or Objective-C++ file, you can declare
NSLog as:
extern void NSLog(CFStringRef format, ...);

then call it as:
NSLog(CFSTR("%d"), val);

This won't port to other OpenStep implementations such as GNUstep.


--
Jens Ayton
.

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