Inheriting initializer from generic class - ios

Question

I've seen some discussions about this problem, but have not read a satisfactory explanation. Can anybody tell me why this does not work?
class Parent<T> {
var data:T
init(data:T) {
self.data = data
}
}
class Child : Parent<Int> {}
let c = Child(data: 4)
The last line gives the error:
'Child' cannot be constructed because it has no accessible initializers
Do I really need to implement the initializer just to call super?
Edit:
To give a bit of context, the real code looks closer to the below. I have an Action class which uses generics, because I have another bit of code which can chain actions together and I want to use Swift's type safety to ensure that actions can be chained. Then I have a bunch of subclasses classes (e.g. CustomAction). I am looking for a way to avoid overriding the init method in each of the subclasses. Or alternatively, I want to understand why that's not possible.
class Action<Input, Output> {
var cachedOutput:Output?
init(cachedOutput:Output?) {
self.cachedOutput = cachedOutput
}
}
protocol CustomInput {}
protocol CustomOutput {}
class CustomAction : Action<CustomInput, CustomOutput> {
}

Answer 1

yes, you really need to override init method ..
class Parent<T> {
var data:T
init(data:T) {
self.data = data
}
}
class Child<T> : Parent<T> {
override init(data: T) {
super.init(data: data)
}
}
let c = Child(data: 4) // Child<Int>
let c2 = Child(data: "alfa") // Child<String>
what are the errors ...
// what is the type T ? it is undeclared!
class Child2: Parent2<T> {}
// how to specialize non-generic type Parent ? how to create it?
// i need an initializer in class Child3 ... Hm ...
class Child3: Parent<Int> {}
// cannot specialize non-generic type 'Parent'
class Child3: Parent<Int> {
override init(data: Int) {
super.init(data: data)
}
}
// So, Child3 must be of the same specialized type as Parent!!
that is terrible, isn't it? so look at my final example !
class Parent<T> {
var data:T
init(data:T) {
self.data = data
}
}
class Child<Double> : Parent<String> {
init(data: Double) {
super.init(data: "\(data)")
}
}
let c = Child(data: 4) // Child<Int> !!!!!
let d = Child(data: true) // Child<Bool> !!!
in your case it works like
class Parent<T> {
var data:T
init(data:T) {
self.data = data
}
}
class Child: Parent<String> {
init(data: Double) {
super.init(data: "\(data)")
}
}
let c = Child(data: 4)
print(c.dynamicType) // Child :-)

Answer 2

This now works in Swift 3. My original example now compiles. There is no mention of this in the Swift 3 Language changes, so I can only assume that this was a bug.