Swift + macro options
I read all the Q&A related to macros in Swift
and I realized that everything in Swift now global,
Am I right?
And my actual question is, if I have a macro where I need parameters to pass, then how can I pass it in the Swift
language?
eg.
Objective-C Macro
#define COLOR_CODE(red, green, blue, alpha) [UIColor colorWithRed: red/255.0 green: green/255.0 blue: blue/255.0 alpha: alpha]
What is the syntax Swift
for the specified macro?
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As 0O0O0O0 mentioned, macros in the sense of "The compiler should see COLOR_CODE(0, 0, 0, 1)
and replace it with [UIColor colorWithRed: 0/255.0 green: 0/255.0 blue: 0/255.0 alpha: 1]
" do not exist in Swift.
Macros in C can be used in ways that lead to confusing error messages:
#define IS_EQUAL_TO_ME(argument) [self isEqual: argument]
BOOL func(id argument) {
return IS_EQUAL_TO_ME(argument);
}
// Error: Use of undeclared identifier 'self'
Or destroy readability:
#define OPEN_BLOCK {
#define CLOSE_WITH_EXIT_IF_FALSE } else { exit (0); }
if (x < 0)
OPEN_BLOCK
return 10;
CLOSE_WITH_EXIT_IF_FALSE
For simple cases such as the COLOR_CODE
recommended strategy for C was to use built-in functions:
NS_INLINE UIColor *ColorCode(CGFloat r, CGFloat g, CGFloat b, CGFloat a) {
return [UIColor colorWithRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:a];
}
This had the same performance as a macro, since it would be tied to the same code, but strongly typed and independent of macro processing rules. This code also has a direct translation into Swift:
func ColorCode(red:CGFloat, green:CGFloat, blue:CGFloat, alpha:CGFloat) -> UIColor {
return UIColor(red: red/255, green: green/255, blue: blue/255, alpha: alpha)
}
Since everything is global, you can declare this in any file and use it in any other file in the same module. In this case, it is up to the compiler to decide whether to include the function.
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You will probably need to convert it to a function or generic, according to this documentation page :
"Complex macros are used in C and Objective-C, but have no analogues in Swift. Complex macros are macros that do not define constants, including function macros in parentheses. You use complex macros in C and Objective-C to avoid the constraints of type checking, or avoid retyping a lot of boilerplate code. However, macros can make debugging and refactoring difficult. In Swift, you can use functions and generics to achieve the same results without any compromise. Therefore, complex macros that are in C and Objective-C source files are not available for your Swift code. "
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What I did was create a class method that returns #define.
Example:
.h file:
#define COLOR_CODE(red, green, blue, alpha) [UIColor colorWithRed: red/255.0 green: green/255.0 blue: blue/255.0 alpha: alpha]
+ (UIColor*)colorCodeWithRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue alpha:(CGFloat)alpha;
.m file:
+ (UIColor*)colorCodeWithRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue alpha:(CGFloat)alpha { return COLOR_CODE(red, green, blue, alpha); }
And in Swift:
Since it is a class method, you can use it in much the same way as #define. If you change your #define macro - it will be reflected in the new method you created In Swift:
let color = YourClass.colorCodeWithRed (72.0, green: 55.0, blue: 100.0, alpha: 1.0);
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