Monday, October 11, 2021

Simplifying Backwards Compatibility in Swift

Dave DeLong:

Every year as new OS and Swift versions are released, the question comes up over and over again: “how do I use this new thing while also supporting older versions?”. While we have a bunch of “availability” tools at our disposal (and I’ll be using them in this post), they always come across as somewhat cumbersome: we need to do inline checks, or we have conditional logic flow that obfuscates the intent of some of our code, and so on.


At first glance, this doesn’t look very useful; it’s a struct that holds a single value, and it doesn’t do anything. This is by design. Backport exists to serve as a holding space (namespace) for shims: the conditional code we must write in order to do proper availability checking.


Unfortunately, I have not come up with a good way to backport things like specific properties on SwiftUI’s EnvironmentValues, such as .headerProminence.

I have typically done this sort of thing by declaring prefixed category methods, but this technique lets you keep the original method name by adding a namespace.


Update (2021-10-19): Christian Tietze:

Behold: @davedelong’s Backport, but for cross platform SwiftUI

Update (2021-11-23): Jesse Squires:

If you are working on a multiplatform SwiftUI project, you will start accumulating #if os() checks and #if canImport() checks. Overtime, these start to accumulate and — in addition to being unsightly — they make your code much more difficult to read. When possible, I have started to encapsulate these preprocessor directives to improve code organization and readability.

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