how to convert interface{} to object in golang?

Question

type Human struct {
     Name string
}

func (t *Human) GetInfo() {
    fmt.Println(t.Name)
}

func main() {
    var p1 interface{}
    p1 = Human{Name:"John"}
    //p1.GetInfo() 
}

now,p1's typs is interface{}, but i want get a Human object.

How to do? i can call p1.GetInfo()

Answer 1

You can use a type assertion to unwrap the value stored in an interface variable. From your example, p1.(Human) would extract a Human value from the variable, or panic if the variable held a different type.

But if your aim is to call methods on whatever is held in the interface variable, you probably don't want to use a plain interface{} variable. Instead, declare the methods you want for the interface type. For instance:

type GetInfoer interface {
    GetInfo()
}

func main() {
    var p1 GetInfoer
    p1 = &Human{Name:"John"}
    p1.GetInfo()
}

Go will then make sure you only assign a value with a GetInfo method to p1, and make sure that the method call invokes the method appropriate to the type stored in the variable. There is no longer a need to use a type assertion, and the code will work with any value implementing the interface.

Answer 2

You can do a type assertion inline:

p1.(*Human).GetAll()

http://play.golang.org/p/ldtVrPnZ79

Or you can create a new variable to hold a Human type.