go（golang）中，如何将接口指针转换为结构指针？

I want to use some external code that requires a pointer to a struct. At the point that the code is called, I have an interface variable.

interface{}*

TestCanGetStructPointer

How can I cast it to this?

Here is a code sample:

import (
    "reflect"
    "testing"
)   

type Cat struct {
    name string
}

type SomethingGeneric struct {
    getSomething func() interface{}
}

func getSomeCat() interface{} {
    return Cat{}
}

var somethingForCats = SomethingGeneric{getSomething: getSomeCat}

func TestCanGetStructPointer(t *testing.T) {
    interfaceVariable := somethingForCats.getSomething()

    pointer := &interfaceVariable

    interfaceVarType := reflect.TypeOf(interfaceVariable)
    structPointerType := reflect.PtrTo(interfaceVarType)
    pointerType := reflect.TypeOf(pointer)

    if pointerType != structPointerType {
        t.Errorf("Pointer type was %v but expected %v", pointerType, structPointerType)
    }

}

The test fails with:

Pointer type was *interface {} but expected *parameterized.Cat

DogCat

Here's a bit of a convoluted/verbose example which avoids that constraint somewhat:

package main

import (
    "fmt"
    "reflect"
)

type Cat struct {
    name string
}

type SomethingGeneric struct {
    getSomething func() interface{}
}

func getSomeCat() interface{} {
    return Cat{name: "Fuzzy Wuzzy"}
}

var somethingForCats = SomethingGeneric{getSomething: getSomeCat}

func main() {
    interfaceVariable := somethingForCats.getSomething()
    castVar := reflect.ValueOf(interfaceVariable)
    castVar.Convert(castVar.Type())

    // If you want a pointer, do this:
    fmt.Println(reflect.PtrTo(castVar.Type()))

    // The deref'd val
    if castVar.Type() != reflect.TypeOf(Cat{}) {
        fmt.Printf("Type was %v but expected %v\n", castVar, reflect.TypeOf(&Cat{}))
    } else {
        fmt.Println(castVar.Field(0))
    }
}