Swift String cast timing comparison

CastTimingComparison.swift

protocol Foo {
	var string: String
}
protocol Bar {
	var string: NSString
}

class FooManager: Manager, Foo {
	var string: String { self.attributedString().string }
}

class BarManager: Manager, Bar {
	var string: NSString { self.attributedString().string as NSString }
}


// 同じNSStringが欲しいときに ↓の2つで所要時間が違う。下の方がちょっと速い。
let string1 = fooManager.string as NSString
let string2 = barManager.string