class car {
var oneWheel : Wheel
func run(inputWheel:Wheel){
oneWheel = inputWheel
....
}
}
I don't want to implement init() and I don't want to initialize the wheel.
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1Declare it as optional, var oneWheel: Wheel?Fred Faust– Fred Faust2016-03-18 03:13:02 +00:00Commented Mar 18, 2016 at 3:13
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Why don't you want to implement init? Are you anti-init?ryantxr– ryantxr2016-03-18 04:06:48 +00:00Commented Mar 18, 2016 at 4:06
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Because I don't like a init(){} dangling in a class and does nothing.user3288177– user32881772016-03-18 16:25:57 +00:00Commented Mar 18, 2016 at 16:25
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2 Answers
Create an implicitly unwrapped optional - this will act like a normal variable but it does not need to be initialised - its initial value is nil. Just ensure the value is set before it is used otherwise you will get a fatal error for unwrapping nil.
class car {
var oneWheel: Wheel!
func run(inputWheel: Wheel) {
wheel = inputWheel
}
}
1 Comment
MikeG
This works. But for someone who is clearly new to optionals, recommending that they use implicitly unwrapped optionals is sending them down a painful path of
unexpectedly found nil while unwrapping an optional valueLike so...
class car {
var oneWheel : Wheel?
// with this version, in order to pass oneWheel into this function as an argument, you will need to unwrap the optional value first. (see below example)
func run(inputWheel:Wheel){
oneWheel = inputWheel
....
}
}
or if you would like the function to take an optional type Wheel as an argument do
class car {
var oneWheel : Wheel?
func run(inputWheel:Wheel?){
//use conditional binding to safely unwrap the optional
if let wheel = inputWheel {
oneWheel = wheel
}
....
}
}
By using conditional binding, instead of an implicitly unwrapped optional, you avoid the potential of crashing due to... unexpectedly found nil while unwrapping an optional value, which occurs when the compiler finds nil where a non-nil value was expected.
