Using Swift's map

In Day 39’ s Moonshot tutorial app, Paul uses .map on an array without much comment about what’s going on. I assume this might be a common concept in modern languages, but it was new to me.

First, here’s Paul’s code

    init(mission: Mission, astronauts: [String: Astronaut]) {
        self.mission = mission

        self.crew = mission.crew.map { member in
            if let astronaut = astronauts[member.name] {
                return CrewMember(role: member.role, astronaut: astronaut)
            } else {
                fatalError("Missing \(member.name)")
            }
        }
    }

Mission here contains an array of crew which is a struct with two strings, one of them being name, but self.crew (which belongs to the view we’re in) is an array of CrewMember which is a struct with a role: String and another struct astronaut. That sounds confusing, but essentially, an array of one type is being processed to return an array of another type where there’s a 1:1 relationship between the elements of each array.

Ranges

I wondered aloud, in a previous post , about the differences in writing a range as

        ForEach(1..<21) {
            Text(String($0))
        }

versus

        ForEach(1...20) {
            Text(String($0))
        }

And that’s been answered in in one of the Day 34 articles. It sounds like older versions of Swift might not have allowed the second version.

How to upgrade XCode and Swift

With the September release of XCode 14 and Swift 5.7 it was time for my first update - I looked in “About” for an update link but there wasn’t one - so if you’re as dense as me, the tip is to head to the Mac App Store and have a look at the Updates page.

Your current XCode version can, of course be found in the XCode | About dialogue. Mine was on 13.4.1. There’s a couple of ways of finding the Swift version - If you’ve got an XCode project open, click on the .xcodeproj in the explorer,and have a look in Build Settings for Swift Compiler - Language for the major version.