golang 断言是什么

func funcName(a interface{}) string {

     return string(a)

}

cannot convert a (type interface{}) to type string: need type assertion

var a interface{}

fmt.Println("Where are you,Jonny?", a.(string))

value, ok := a.(string)

value, ok := a.(string)

if !ok {

    fmt.Println("It's not ok for type string")

    return

}

fmt.Println("The value is ", value)

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

}

var (

   a string

   b int

   c int64

   ...

)

import (

    "fmt"

    "strings"

    "net/http"

   ...

)