有没有一种方法可以从字符串创建结构实例？

Question

Given a struct:

type MyStruct struct {
    A int
    B int
}

and a string with the struct's name

a := "MyStruct"

or

a := "mypkg.MyStruct"

How do I create an instance of my struct from the string name rather than the struct? The idea is that I would create an application with all of the structures linked into the binary but create the runtime instances from the strings. (sort of a meta-meta)

Answer 1

There is no central registry of types in Go, so what you ask is impossible in the general case.

You could build up your own registry by hand to support such a feature using a map from strings to reflect.Type values corresponding to each type. For instance:

var typeRegistry = make(map[string]reflect.Type)

func init() {
    myTypes := []interface{}{MyString{}}
    for _, v := range myTypes {
        // typeRegistry["MyString"] = reflect.TypeOf(MyString{})
        typeRegistry[fmt.Sprintf("%T", v)] = reflect.TypeOf(v)
    }
}

You can then create instances of the types like so:

func makeInstance(name string) interface{} {
    v := reflect.New(typeRegistry[name]).Elem()
    // Maybe fill in fields here if necessary
    return v.Interface()
}