Explit conformance to Codable removes memberwise initializer generation on structs

问题

Given:

struct Foo {
    let bar: Bar
}

I get a convenience initializer to use:

let foo = Foo(bar: Bar())

But if Bar isn't itself Codable, or for some other reason I need to explicitly implement Codable on Foo then the convenience memberwise initializer is no longer present:

struct Foo: Codable {

    init(from decoder: Decoder) throws {

    }

    func encode(to encoder: Encoder) throws {

    }

    let bar: Bar
}

and i get:

let foo = Foo(bar: Bar())

Incorrect argument label in call (have 'bar:', expected 'from:')

---

Is it possible to have the best of both worlds here?

回答1:

You can implement the Codable conformance in an extension.

When adding any struct initializer in an extension, the memberwise initializer will not be removed.

struct MyStruct {
    var name: String
}
extension MyStruct: Codable {} // preserves memberwise initializer

MyStruct(name: "Tim")

来源：https://stackoverflow.com/questions/48155118/explit-conformance-to-codable-removes-memberwise-initializer-generation-on-struc