基于字符串的断言类型？

Question

Suppose I have the following:

type T struct { Name string }

Then I create a var of type T:

thing := T{"Hello World"}

I then reflect the type:

t := reflect.TypeOf(thing) // main.T

Then I pass t in to a method that accepts an interface, is there any way I can then say, in that method, that the accepted interface{} is of type main.T if I have that string?

The use case is I have a json string that fits a type. I have a string of that type ( main.T ) and I want to be able to create a new variable that is of type main.t when I only know of the string, main.T then marshal the data to that new variable.

Answer 1

The Go runtime does not provide a way to create a value given the name of a type, but that's something you can implement in the application:

var types = map[string]reflect.Type{
    "main.T": reflect.TypeOf((*T)(nil)).Elem(),
}

You can create a new value given the name using:

v := reflect.New(types[name]).Interface()

This assumes that name is a valid name. You may want to check for the case where types[name] == nil.

playground example

You can also do this without reflection:

var types = map[string]func() interface{} {
    "main.T": func() interface{} { return &T{} }
}

v := types[name]()