復合類型可以由多個對象類型構成，主要用于縮短已有對象成員的簽名。 <br/> **語法：** ```scala A with B with C with ... ``` ```scala object App{ def main(args: Array[String]): Unit = { trait X1 trait X2 trait X3 // 定義復合類型參數x def test(x: X1 with X2 with X3): Unit = { println("OK") } // 函數調用，實參為匿名對象 test(new X1 with X2 with X3) // OK object A extends X1 with X2 with X3 // 函數調用，實參為單例對象 test(A) // OK } } ```