class Subjects { var physics: String init(physics: String) { self.physics = physics } } class Chemistry: Subjects { var equations: String init(physics: String, equations: String) { self.equations = equations super.init(physics: physics) } } class Maths: Subjects { var formulae: String init(physics: String, formulae: String) { self.formulae = formulae super.init(physics: physics) } } let sa = [ Chemistry(physics: "固体物理", equations: "赫兹"), Maths(physics: "流体动力学", formulae: "千兆赫")] let samplechem = Chemistry(physics: "固体物理", equations: "赫兹") print("实例物理学是: \(samplechem.physics)") print("实例方程式: \(samplechem.equations)") let samplemaths = Maths(physics: "流体动力学", formulae: "千兆赫") print("实例物理学是: \(samplemaths.physics)") print("实例公式是: \(samplemaths.formulae)")