The question is if we can solve the problem with special private init() and
convenience inits ?
class MyBase {
init () {
}
}
class MyClass : MyBase {
let x:Int
let y:String
let z:Double
private init(_ xValue: Int, _ zValue: Double) {
self.x = xValue
self.y = "\(xValue) - \(zValue)"
self.z = zValue
super.init()
}
convenience override init() {
self.init(1, 1.0)
}
convenience init(x: Int) {
self.init(x, 1.0)
}
convenience init(z: Double) {
self.init(1, z)
}
}
print(MyClass().y)
print(MyClass(x: 10).y)
print(MyClass(z: 10.0).y)
Seems like we can. Any drawbacks?
On 16.06.2016 9:27, Jonathan Hull via swift-evolution wrote:
I don’t remember a proposal for that, but I would definitely support one.
I use this pattern all the time (usually by initializing to a default
value first), and it would be nice to have an explicit/safe way to handle
it, (and to avoid waisting cycles creating an object I never use).
Perhaps we should spell it @init or @initHelp:
class MyClass : MySuperClass {
let x:Int
let y:String
let z:Double
@init func commonSetup() {
self.y = “My String”
self.z = 4.2
}
init(x: Int) {
self.x = x
commonSetup() //No error because commonSetup() sets the value of
‘y’ & ‘z'
super.init()
}
}
Basically the @init functions would be inlined into the init. They would
only be callable from inits, and could only be called a single time within
each init.
Thanks,
Jon
I believe there was(was?) already a suggestion to introduce special methods
that could be called from initializers. IMO this is a better solution to
the problem as you really should not call 'usual' instance method until the
instance is fully instantiated(super.init() called in your case):
class MyClass : MySuperClass {
let x : Int
let y : String //let!
initfunc calcY(somePatam: Int) -> String {
return ....
}
init(x: Int) {
self.x = x
self.y = assignY(5)
super.init()
}
}
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