I'm looking for a way to add a default initializer to a protocol via protocol extensions.
My protocol is:
protocol TestProtocol {
var myVar : Double { get set }
init(value: Double)
init(existingStruct : TestProtocol)
}
I've implemented a struct using this protocol as:
struct TestStruct : TestProtocol {
var myVar : Double
init(value : Double) {
myVar = value
}
init (existingStruct : TestProtocol) {
myVar = existingStruct.myVar
}
}
However if I try via extension to make a default initializer for this protocol I run into self issues:
extension TestProtocol {
init(value : Double) {
myVar = value
}
init(existingStruct : TestProtocol) {
myVar = existingStruct.myVar
}
}
Where both assignment lines issue the error Variable 'self' passed by reference before being initialized
Is there a way to make this work - or am i limited to using classes?
Your question is almost the same as in this post I answered yesterday.
Here is the trick to solve this :)
protocol TestProtocol {
var myVar : Double { get set }
init() // designated initializer which will ensure that your class or structer type will instantiate correctly
}
struct TestStruct : TestProtocol {
var myVar : Double
init() {
myVar = 0
}
}
extension TestProtocol {
init(value : Double) {
self.init()
myVar = value
}
init(existingStruct : TestProtocol) {
self.init()
myVar = existingStruct.myVar
}
}
Have a good day. :) Protocol extension is so nice.
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