Temperature.celsiusValue should be a computed property

[stephencelis]

The problem with a lazy var is you can overwrite it:

Tropos/Tropos/Models/Temperature.swift

Lines 19 to 21 in 877990c

	lazy var celsiusValue: Int = {
	return Int(round(Float(self.fahrenheitValue - 32) * 5.0 / 9.0))
	}()

let temp = Temperature(fahrenheitValue: 20)
temp.celsiusValue = 20

The math isn't particularly expensive, so using a computed variable is probably good enough. If we really want to lazily load the celsius value, we can do so with a private lazy var, which the computed variable calls/returns.

[jakecraige]

Interesting find. Computed variable makes sense to me.