Swift 4.1 implemented SE-0075, which introduced a new canImport condition that lets us check whether a specific module can be imported when our code is compiled.
This is particularly important for cross-platform code: if you had a Swift file that implemented one behavior on macOS and another on iOS, or if you needed specific functionality for Linux. For example:
#if canImport(SpriteKit)
// this will be true for iOS, macOS, tvOS, and watchOS
#else
// this will be true for other platforms, such as Linux
#endifPreviously you would have had to use inclusive or exclusive tests by operating system, like this:
#if !os(Linux)
// Matches macOS, iOS, watchOS, tvOS, and any other future platforms
#endif
#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
// Matches only Apple platforms, but needs to be kept up to date as new platforms are added
#endifThe new canImport condition lets us focus on the functionality we care about rather than what platform we're compiling for, thus avoiding a variety of problems.
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Other changes in Swift 4.1…
- Synthesized Equatable and Hashable
- Key decoding strategies for Codable
- Conditional conformances
- Recursive constraints on associated types
- Target environment testing
- flatMap is now (partly) compactMap()
Download all Swift 4.1 changes as a playground Link to Swift 4.1 changes
