#ifdef replacement in the Swift language

Question

In C/C++/Objective C you can define a macro using compiler preprocessors. Moreover, you can include/exclude some parts of code using compiler preprocessors.

Answer 1

There is no Swift preprocessor. (For one thing, arbitrary code substitution breaks type- and memory-safety.)

Swift does include build-time configuration options, though, so you can conditionally include code for certain platforms or build styles or in response to flags you define with -D compiler args. Unlike with C, though, a conditionally compiled section of your code must be syntactically complete. There's a section about this in Using Swift With Cocoa and Objective-C.

For example:

#if os(iOS)
    let color = UIColor.redColor()
#else
    let color = NSColor.redColor()
#endif