2017-10-09 using reduce in Swift

Here's a little playground that shows how to use reduce in Swift, specifically use it to report on a bunch of booleans. In the following code, we use reduce to determine whether all objects are enabled, or whether at least one is enabled.

    struct MyStruct {
        var enabled: Bool
        var text: String
    }

    let collection = [
        MyStruct(enabled: true, text: "one"),
        MyStruct(enabled: false, text: "two"),
        MyStruct(enabled: true, text: "three"),
    ]

    let enabledArray = collection.map { $0.enabled }

    let allEnabled = enabledArray.reduce(true) { $0 && $1 }
    print(allEnabled)

    let oneEnabled = enabledArray.reduce(false) { $0 || $1 }
    print(oneEnabled)

I've used this when I had a bunch of UITextField instances. Some of them were enabled, some not (i.e. property isEnabled set to true or false). Or for example when you have a bunch of UIView instances; are none of them hidden? That sort of stuff.

I could've posted this example with just an array of booleans as input, but I wanted to demonstrate the map as well. Often you don't just have a bare array of booleans.

One minor thing with the allEnabled variable in the example is that its result is meaningless when applied to an empty array. It'll return true. But what does that mean, right? You'll have to decide for yourself.