struct literal uses unkeyed fields

Question

My goal is to embed function to an existing type.

The problem is it warns var parent *embedding.Parent github.com/kidfrom/learn-golang/embedding.Child struct literal uses unkeyed fields.

The current solution is to create NewChild(parent *Parent) *Child. However, I am afraid that this is just tricking the compiler and in the future it will panic unexpectedly, so what am I doing wrong?

func NewChild(parent *Parent) *Child { return &Child{parent} }

cmd/test/main.go

package main import "github.com/kidfrom/learn-golang/embedding" func main() { parent := &embedding.Parent{} child := &embedding.Child{parent} // it warns `var parent *embedding.Parent github.com/kidfrom/learn-golang/embedding.Child struct literal uses unkeyed fields` child.CallParentMethod() }

embedding.go

package embedding import "fmt" type Parent struct{} func (p *Parent) parentMethod() { fmt.Println("parent method") } type Child struct { *Parent } func (c *Child) CallParentMethod() { c.parentMethod() }

Good explanation here: stackoverflow.com/a/63747469/2190251

FelixEnescu
– FelixEnescu

2023-02-12 09:40:41 +00:00
Commented Feb 12, 2023 at 9:40 — FelixEnescu
– FelixEnescu, Commented Feb 12, 2023 at 9:40

colm.anseo · Accepted Answer · 2022-09-23 12:46:16Z

The warning you are getting is most likely from go-staticcheck. You'd also see a similar warning by running:

$ go vet ./main.go:8:12: github.com/kidfrom/learn-golang/embedding.Child composite literal uses unkeyed fields

Checking the docs of the package you are importing:

$ go doc "github.com/kidfrom/learn-golang/embedding" Child package embedding // import "github.com/kidfrom/learn-golang/embedding" type Child struct { *Parent } func NewChild(parent *Parent) *Child func (c *Child) CallParentMethod()

shows the embedded type within Child is Parent, so to fix the warning explicitly assign the value to this (embedded struct) field:

child := &embedding.Child{Parent: parent}

faschulze · Accepted Answer · 2022-09-23 12:46:10Z

You can fix the warning by adding a key to your *Parent attribute within the Child struct. Example:

type Child struct { Parent *Parent }

and adjust the initialization of your child attribute in your main func as followed:

child := &embedding.Child{Parent: parent}

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