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Units and Measurement

Units and measurements

  • struct Measurement:A numeric quantity labeled with a unit of measure, with support for unit conversion and unit-aware calculations.
  • class Unit: An abstract class representing a unit of measure.
  • class Dimension: An abstract class representing a dimensional unit of measure.

Dimension

Dimension allows you to easily convert between units and display the unit symbol.

import Foundation

let distance = 1234.0 // meters as a double
let distMeters = Measurement(value: distance, unit: UnitLength.meters)
let distMiles = distMeters.converted(to: .miles).value

Creating New Custom Units

You also have the ability to create new custom units. For some reason, angular velocity is not included in the library, so let's make some:

let radiansPerSecond = UnitFrequency(symbol: "rps", converter: UnitConverterLinear(coefficient: 1/(2*3.14)))
let degreesPerSecond = UnitFrequency(symbol: "dps", converter: UnitConverterLinear(coefficient: 1/(360)))

let r = Measurement(value: 3.14, unit: radiansPerSecond)
r.converted(to: .hertz).value
r.converted(to: degreesPerSecond)

Creating New Units Not in Foundation

For something that doesn't exist in Foundation, you can create a whole new unit. For example, the unit for radioactivity is not found:

class CustomRadioactivityUnit: Dimension {
    static let becquerel = CustomRadioactivityUnit(
        symbol: "Bq",
        converter: UnitConverterLinear(coefficient: 1.0))
    static let curie = CustomRadioactivityUnit(
        symbol: "Ci",
        converter: UnitConverterLinear(coefficient: 3.7e10))

    static let baseUnit = CustomRadioactivityUnit.becquerel
}

let rad = Measurement(value: 2, unit: CustomRadioactivityUnit.becquerel)