#swift StringInterpolationConvertibleの挙動を確認

StringInterpolationConvertible.swift

import Foundation

class C {}

// support own class without Printable
extension String {
    init(stringInterpolationSegment expr: C) {
        self.init(format: "C(%d)", ObjectIdentifier(expr).hashValue)
    }
}
let c = C()
String(stringInterpolationSegment: c) // "C(1137743216)
"\(c)" // "C(1137743216)

// Create own type support StringInterpolationConvertible
struct Interpolation: StringInterpolationConvertible {
    var identifiers = [String]()
    init<T>(stringInterpolationSegment expr: T) {
        println("generic") // (2 times)
        identifiers = [String(stringInterpolationSegment: expr)]
    }
    init(stringInterpolation strings: Interpolation...) {
        println("non generic")
        identifiers = strings.flatMap {
            $0.identifiers // (2 times)
        }
    }
}

let i: Interpolation = "test\(C())\(1+1)" // {["test","__lldb_expr_511.C", "2"]}
i.identifiers // ["test","__lldb_expr_511.C", "2"]