如何在mapstructure.decode中传递结构字段的指针

Question

I am trying to decode a map into a struct type with help of mapstructure library. If I do it with plain variable it decodes ok, but if I pass struct field it does not decode the map:

package main

import (
    "github.com/mitchellh/mapstructure"
)

type Person struct {
    Name string
}

type Bundle struct {
    Name string
    Struct interface{}
}

func main() {
    p_map := map[string]string{
        "Name": "John",
    }

    p := Person{}
    mapstructure.Decode(p_map, &p)

    print(p.Name) // shows name John

    b := Bundle{
        "person"
        Person{},
    }

    mapstructure.Decode(p_map, &b.Struct)

    print(b.Struct.(Person).Name) // Does not show any name. Blank

}

Could you please clarify if I am passing wrong storage for map decoding or it is just mapstructure limitation and I am not able to decode maps into struct fields? Thank you!

UPD

I am sorry if I was not clear enough about the actual reason I need to use such flow:

I send HTTP requests to different resources and get various objects with different fields so initially I collect them as interface{}. After I get a particular resource object, I need to convert it into a particular struct (Person in my sample) so I use mapstructure.decode() function for that.

As I have various objects that are decoded in different structures I want to create a loop in order to avoid code duplication. What I wanted to do is to create a slice with different structures like:

bundles := []Bundle{
    {"person", Person{}}
    {"employee", Employee{}}
    ...
}

And then decode objects in a loop:

for bundle := range bundles {
    // map_storage contains different type maps that are going to be decoded into struct and key for the specific object is bundle name
    mapstructure.Decode(maps_storage[bundle.Name], &bundle.Struct)

    // bundle.Struct blank, but I expect that it is filled as in the example below
}

Answer 1

I think you must slightly change the implementation

var p1 Person

mapstructure.Decode(p_map, &p1)
b := Bundle{
    p1,
}

print(b.Struct.(Person).Name) // John will appear

I'm trying your code above but lead to empty Person. Maybe Decode function cannot change real value of b.Struct(I'm not sure the exact reason, this is just my opinion), but if I decode to struct Person first then assign to Bundle that works.

Updated: with some research, I found out the problem.You must use pointer instead of struct. here the updated code

package main

import (
    "github.com/mitchellh/mapstructure"
)

type Person struct {
    Name string
}

type Bundle struct {
    Name   string
    Struct interface{}
}

func main() {
    p_map := map[string]string{
        "Name": "John",
    }

    p := &Person{}
    mapstructure.Decode(p_map, &p)

    print(p.Name) // shows name John

    b := Bundle{
        "person",
        &Person{},
    }

    mapstructure.Decode(p_map, &b.Struct)

    print(b.Struct.(*Person).Name) // Does not show any name. Blank

}