golang还有一种特殊形式来检测接口变量的类型—swtich：

    1. switch t := areaIntf.(type) {
    2. case *Square:
    3.     fmt.Printf("Type Square %T with value %v\n", t, t)
    4. case *Circle:
    5.     fmt.Printf("Type Circle %T with value %v\n", t, t)
    6. case nil:
    7.     fmt.Printf("nil value: nothing to check?\n")
    8. default:
    9.     fmt.Printf("Unexpected type %T\n", t)
    10. }

    如果仅仅是测试变量的类型， 不用它的值，那么可以不需要赋值：

    1. switch areaIntf.(type) {
    2. case *Square:
    3.     // TODO
    4. case *Circle:
    5.     // TODO
    6. ...
    7. default:
    8.     // TODO
    9. }

    example：

    1. func classifier(items ...interface{}) {
    2.     for i, x := range items {
    3.         switch x.(type) {
    4.         case bool:
    5.             fmt.Printf("Param #%d is a bool\n", i)
    6.         case float64:
    7.             fmt.Printf("Param #%d is a float64\n", i)
    8.         case int, int64:
    9.             fmt.Printf("Param #%d is a int\n", i)
    10.         case nil:
    11.             fmt.Printf("Param #%d is a nil\n", i)
    12.         case string:
    13.             fmt.Printf("Param #%d is a string\n", i)
    14.         default:
    15.             fmt.Printf("Param #%d is unknown\n", i)
    16.         }
    17.     }
    18. }