Standard way to “clamp” a number between two values in Swift

Question

Given:

let a = 4.2
let b = -1.3
let c = 6.4

I want to know the simplest, Swiftiest way to clamp these values to a given range, say 0...

Answer 1

The shortest (but maybe not most efficient) way to clamp, is:

let clamped = [0, a, 5].sorted()[1]

Source: user tobr in a discussion on Hacker News

Answer 2

With Swift 5.1, the idiomatic way to achieve the desired clamping would be with property wrappers. A touched-up example from NSHipster:

@propertyWrapper
struct Clamping<Value: Comparable> {
  var value: Value
  let range: ClosedRange<Value>

  init(wrappedValue: Value, _ range: ClosedRange<Value>) {
    precondition(range.contains(wrappedValue))
    self.value = wrappedValue
    self.range = range
  }

  var wrappedValue: Value {
    get { value }
    set { value = min(max(range.lowerBound, newValue), range.upperBound) }
  }
}

Usage:

@Clamping(0...5) var a: Float = 4.2
@Clamping(0...5) var b: Float = -1.3
@Clamping(0...5) var c: Float = 6.4