On Thu, Apr 28, 2022 at 9:49 AM Glen D souza <glenpo...@gmail.com> wrote:
> Consider the following piece of code
>
> type Dog struct {
> }
>
> type Walker interface {
> Walks()
> }
>
> func (d *Dog) Walks() {
>
> }
>
> func CheckWalker(w Walker) {
>
> }
>
> func main() {
> dog := Dog{}
> CheckWalker(dog) -> cannot use dog (variable of type Dog) as Walker
> value in argument to CheckWalker: Dog does not implement Walker (method
> Walks has pointer receiver)compilerInvalidIfaceAssign
> <https://pkg.go.dev/golang.org/x/tools/internal/typesinternal?utm_source%3Dgopls#InvalidIfaceAssign>
> }
>
> When I run this code I get the error as show in the red above
>
> Now consider this piece of code
>
> type Dog struct {
> }
>
> func (d *Dog) Walks() {
>
> }
>
> type Bird struct {
> }
>
> func (b *Bird) Flys() {
>
> }
>
> type Flyer interface {
> Flys()
> }
>
> type Walker interface {
> Walks()
> }
>
> type Combined interface {
> Walker
> Flyer
> }
>
> type Animal struct {
> Dog
> Bird
> }
>
Look at the Animal struct. The Walks and Flys methods are defined for
*Animal, not for Animal. The type Animal has no methods. Because of that,
*Animal implements the combined interface, and not Animal.
In your main(), you declare animal=&Animal{}, thus the variable `animal`
can be used where Combined is required.
>
> func CheckCombined(c Combined) {
>
> }
>
> func Check(w Walker) {
>
> }
> func main() {
> animal := &Animal{}
> CheckCombined(animal)
> }
>
> This code runs without any error!
> Since Animal struct is compose of Dog and Bird (not pointer to them), why
> this code is working where as only pointer to Dog and Bird implement the
> necessary methods to satisfy the interface Combined ?
>
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>
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