Why Does My Go Method with a Pointer Receiver Fail to Implement an Interface?

Golang Method with Pointer Receiver [Duplicate]

Problem:

In Go, when creating a method with a pointer receiver and implementing an interface, the following error can occur:

cannot use obj (type Implementation) as type IFace in return argument: Implementation does not implement IFace (GetSomeField method has pointer receiver)

Answer:

To resolve this error, ensure that the pointer to the struct implements the interface. This allows the method to modify the fields of the actual instance without creating a copy.

Code Modification:

Replace the offending line with:

return &obj

Explanation:

By returning a pointer to the struct, it implements the interface while allowing the method to modify the actual instance.

Example (Modified):

package main

import (
    "fmt"
)

type IFace interface {
    SetSomeField(newValue string)
    GetSomeField() string
}

type Implementation struct {
    someField string
}

func (i *Implementation) GetSomeField() string {
    return i.someField
}

func (i *Implementation) SetSomeField(newValue string) {
    i.someField = newValue
}

func Create() *Implementation {
    return &Implementation{someField: "Hello"}
}

func main() {
    var a IFace
    a = Create()
    a.SetSomeField("World")
    fmt.Println(a.GetSomeField())
}

By using a pointer receiver and ensuring the pointer implements the interface, you can successfully modify the actual instance of the struct while implementing the required methods.

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