📦Measurement

🏖️ 試玩

import Foundation  // Measurement

/* ------- Custom Extensions ------- */

extension Double {
    /// usage: `6.ft`
    var ft: Measurement<UnitLength> {
        Measurement(value: self, unit: UnitLength.feet)
    }
    /// usage: `180.deg`
    var deg: Measurement<UnitAngle> {
        Measurement(value: self, unit: UnitAngle.degrees)
    }
    /// usage: `4.m²`
    var m²: Measurement<UnitArea> {
        Measurement(value: self, unit: UnitArea.squareMeters)
    }
}

extension Measurement where UnitType: Dimension {
    /// usage: `6.ft.in(.centimeters)`
    func `in`(_ otherUnit: UnitType)  -> Measurement<UnitType> {
        converted(to: otherUnit)
    }
}

// ----------------------------------------

// length
let h1 = Measurement(value: 6, unit: UnitLength.feet)
let h2 = h1.converted(to: UnitLength.inches)
let h3 = h1.converted(to: UnitLength.meters)

h1 == h2  // true
h2 == h3  // true

let h = 6.ft
let h4 = h.in(.centimeters)
"\(h) = \(h4)"         // 6.0 ft = 182.8800...002 cm

// ❌ 兩個測量值 (Measurement) 不能直接運算，看來使用起來限制不小。
// let hSqaured = h * h

// angle
let degrees = Measurement(value: 180, unit: UnitAngle.degrees)
let radians = degrees.converted(to: .radians)

let a = 180.deg
let a1 = a.in(.radians)
"\(a) = \(a1)"          // 180.0° = 3.1415...9798 rad

// area
let squareMeters = Measurement(value: 4, unit: UnitArea.squareMeters)
let squareCentimeters = squareMeters.converted(to: .squareCentimeters)

let b = 4.m²
let b2 = b.in(.squareCentimeters)
"\(b) = \(b2)"          // 4.0 m² = 40000.0 cm²

// volumn
let bushels = Measurement(value: 6, unit: UnitVolume.bushels)
let teaspoons = bushels.converted(to: .imperialTeaspoons)

🍎 官方

• Foundation > Units and Measurement

  • Measurement

📘 參考

• How to convert units using Unit and Measurement - Hacking with Swift

👥 相關

• @KilometersPerHour

定義

struct Measurement<UnitType: Unit>