CODEWITHSUNDEEP
go
vinllen
vinllen

Reputation: 1459

Convert struct to base class

In my understanding, there is no inherent and polymorphism in golang, so how to get the sub-struct from a given struct? For example, struct A has several attributes:

type A struct {
    a int
    b string
    c *float64
    d []byte
    e map[string]interface{}
}

I want to delete the e:

type B struct {
    a int
    b string
    c *float64
    d []byte
}

So is there any way to convert A to B except copy variables one by one?

Upvotes: 0

Views: 1643

Answers (1)

jrefior
jrefior

Reputation: 4421

You can do that with embedded fields. See Struct Types in the Go Language Specification, e.g.:

Field names may be specified explicitly (IdentifierList) or implicitly (EmbeddedField).

With an embedded field, you can copy the fields in one struct to the struct in which it is an embedded field with a simple assignment to the field.

Here's a complete, runnable example:

package main

import (
    "encoding/json"
    "fmt"
)

type Shared struct {
    Id   int
    Name string
}

type A struct {
    Count int
    Shared
}

type B struct {
    Color string
    Shared
}

func main() {
    shared := Shared{
        Id:   1,
        Name: "john",
    }
    a := A{
        Count:  5,
        Shared: shared,
    }
    b := B{
        Color: "green",
    }
    b.Shared = a.Shared
    c := map[string]interface{}{
        `a`: a,
        `b`: b,
    }
    msg, err := json.Marshal(c)
    if err != nil {
        fmt.Printf("Marshal error: %s\n", err)
    }
    fmt.Println(string(msg))
}

Prints:

{"a":{"Count":5,"Id":1,"Name":"john"},"b":{"Color":"green","Id":1,"Name":"john"}}

Upvotes: 2

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