Alias Type Definitions do not Inherit Underlying Type Methods

Evan Hicks

—July 12, 2022

The ProblemThe Problem

Type definitions do not inherit underlying type methods.
Compile Error: ./prog.go:17:3: b.Print undefined (type Bar has no field or method Print)

Click to Copy

package main

import (
    "fmt"
)

type Foo struct{}

func (f Foo) Print() {
    fmt.Println("foo")
}

type Bar Foo

func main() {
    b := Bar{}
    b.Print()
}

Go does not have traditional inheritance like other languages, therefore the alias type declaration type Bar Foo works differently in Go. When you create a new type based on another type, your new type (Bar) doesn’t inherit the methods from Foo, which is why b.Print is undefined.

The fix:

Click to Copy

package main

import (
    "fmt"
)

type Foo struct{}

func (f Foo) Print() {
    fmt.Println("foo")
}

type Bar struct {
    Foo
}

func main() {
    b := Bar{}
    b.Print()
}

This creates a new type Bar, and embeds it with an implicit Foo object. In this case, when you call a method on a Bar object, it will check to see if Bar has that method, and if it doesn’t, it will check Foo for the method and use that.

Platform

Languages & Frameworks

Why Sentry?

Alias Type Definitions do not Inherit Underlying Type Methods

The ProblemThe Problem

The SolutionThe Solution

Further ReadingFurther Reading

Alias Type Definitions do not Inherit Underlying Type Methods

The SolutionThe Solution

Further ReadingFurther Reading

A peek at your privacy

Who we collect PII from

PII we may collect about you

How we use your PII

Third parties who receive your PII

We use cookies (but not for advertising)

Know your rights