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swiftswift-protocolsconditional-compilation

Compile-time conditional protocol conformance in Swift

I have a Swift class that, under certain compile-time conditions, should implement a certain protocol. I expected that conditional complication #if checks would work, with something like this:

class MyClass
#if SOME_COMPILE_TIME_CHECK
: SomeProtocol
#endif
{
  // ...

  #if SOME_COMPILE_TIME_CHECK
  func someMethodToImplementSomeProtocol() { }
  #endif
}

This does not work. The compiler tries to compile each conditional block as a series of statements. But the block : SomeProtocol does not parse as a series of statements.

Is there another way to express this? For example, is there a statement-level way to express that "MyClass implements SomeProtocol"?

Solution

  • Put it in an extension:

    #if SOME_COMPILE_TIME_CHECK
extension MyClass : SomeProtocol {
    func someMethodToImplementSomeProtocol() { }
}
#endif