I busy rewriting an app in Swift and would like to convert the following macro to Swift code.
#define FLOG(format, ...) NSLog(@"%@.%@ %@", [self class], NSStringFromSelector(_cmd), [NSString stringWithFormat:format, ##__VA_ARGS__])
How can I define this as a Swift function such that I can use if anywhere for debug logging purposes, or is there an alternate way to achieve the same thing?
The easiest way is probably to take advantage of string interpolation and use:
func FLOG(message:String, method:String = __FUNCTION__) {
println("\(method): \(message)")
}
Then you usage is similar to:
FLOG("Illegal value: \(value)")
Having the method argument default to __FUNCTION__ means that it will normally be replaced with the calling function name. Other automatic variables that you could use include __FILE__, __LINE__ and __COLUMN__. Unfortunately __PRETTY_FUNCTION__ is no longer available.
If you want more control over the formatting of the message than string interpolation allows, take a look at this question which demonstrates simplifying access to printf-style formatting in Swift, and would let you do:
FLOG("Illegal value: %x" % [value])
See also this post from Apple that addresses using __FILE__ and __LINE__ in assert
Apple's answer to the removal of macros and something new to replace them is that nothing like macros will be available in swift. The closest you can get is to replace #define with a global let variable.
Example: instead of #define CONSTANT 0 you can write let CONSTANT = 0
Whereas, if you want to pass arguments inside a macro, that feature will no longer be available as considered bad programming practice. What you can do instead is create a function.
