Golang类型switch

在群里讨论到了这个问题

然后下面这是官方给出的例子

var t interface{}
t = functionOfSomeType()
switch t := t.(type) {
default:
    fmt.Printf("unexpected type %T", t)       // %T prints whatever type t has
case bool:
    fmt.Printf("boolean %t\n", t)             // t has type bool
case int:
    fmt.Printf("integer %d\n", t)             // t has type int
case *bool:
    fmt.Printf("pointer to boolean %t\n", *t) // t has type *bool
case *int:
    fmt.Printf("pointer to integer %d\n", *t) // t has type *int
}

里面有几点要注意一下

在switch t := t.(type)时

switch的其实是t.(type)而不是被创建的t

然后t := t.(type)创建的是类型为t.(type)，值为t的值的一个变量

里面所使用的t都是switch里新建的那个t

等于下面这个例子

var t interface{}
t = functionOfSomeType()
switch t.(type) {
default:
    fmt.Printf("unexpected type %T", t)       // %T prints whatever type t has
case bool:
    t := t.(bool)
    fmt.Printf("boolean %t\n", t)             // t has type bool
case int:
    t := t.(int)
    fmt.Printf("integer %d\n", t)             // t has type int
case *bool:
    t := t.(*bool)
    fmt.Printf("pointer to boolean %t\n", *t) // t has type *bool
case *int:
    t := t.(*int)
    fmt.Printf("pointer to integer %d\n", *t) // t has type *int
}