I want to try to write a default init in a protocol extension, so I did this:
protocol P {
var data: [AnyHashable: Any] { get }
init(_ s: String)
}
extension P {
init(_ s: String) {
self.data = ["s": s]
}
}
But I'm getting this error:
'let' property 'data' may not be initialized directly; use "self.init(...)" or "self = ..." instead
I have no idea what it means. Thanks for your help!
The error says that the variable cannot be initialized in the protocol extension because it's declared as constant { get }
But even if you declare the variable { get set } you can't use the init method anyway without a constraint to a concrete type or an associated type.
import PlaygroundSupport
protocol P {
var data: [AnyHashable: Any] { get }
var _data: [AnyHashable: Any] { get set }
static func generator(_ s: String) -> P
init()
}
extension P {
static func generator(_ s: String) -> P {
var p = self.init()
p._data = ["s": s]
return p
}
}
class A: P {
required init() { }
var data: [AnyHashable : Any] {
return _data
}
var _data: [AnyHashable : Any] = [:]
}
let a = A.generator("some")
print(a.data)
PlaygroundPage.current.finishExecution()
I think this is the closest code you want. The problem is that _data is shared by other classes.