According this question, golang will generate both type-receiver method and point-receiver method, which means the code below will work correctly and the value will change unexpectedly.
func (test *Test) modify() {
test.a++
}
func main() {
test := Test{10}
fmt.Println(test)
test.modify()
fmt.Println(test)
}
I think it's acceptable to me. But when this mixes with interface, thing goes wrong.
type Modifiable interface {
modify()
}
type Test struct {
a int
}
func (test *Test) modify() {
test.a++
}
func main() {
test := Test{10}
fmt.Println(test)
test.modify()
fmt.Println(test)
var a Modifiable
a = test
}
it said:
Test does not implement Modifiable (modify method has pointer receiver)
Why will this happen ?
And how golang actually handle method call ?
When you said:
func (test *Test) modify() {
test.a++
}
It means the interface Modifiable is implemented by the type *Test aka the Pointer to Test
Where as
func (test Test) modify() {
test.a++
}
means that the interface is implemented by the type Test
Conclusion is: A type and a pointer to that type are 2 different types.
if you wanted to use a method that has pointer receiver. It means you have to pass the address value.
here is the example :
package main
import "fmt"
type Modifiable interface {
modify()
}
type Test struct {
a int
}
func (test *Test) modify() {
test.a++
}
func main() {
test := Test{10}
fmt.Println(test)
test.modify()
fmt.Println(test)
var a Modifiable
a = &test
a.modify()
fmt.Println(a)
}
In conclusion an interface will accept the address value whenever you create a pointer receiver in the method.