type IA interface {
Method()
}
type SA struct {
}
func (this *SA) Method() {
}
func main() {
var i IA = SA{} //error
var i IA = &SA{} //ok
var obj = SA{}
obj.Method()//ok
}
Could you explain why does GO automatically dereference in the case of calling function (obj.Method()) but in assignment to interface variable (var i IA = SA{}) it can't?
func (this *SA) Method() means that only a pointer to type SA (*SA) has the Method() method, therefore var i IA = &SA{} fulfils the IA interface.
If you change it to read func (this SA) Method() then var i IA = SA{} fulfils the interface, and not var i IA = &SA{}.
*SA is not the same type as SA.
Go provides some shortcuts for dealing with dereferencing method values (which is probably where the confusion is coming from)
If you have a look at the Method Values section of the spec you will see that:
a reference to a non-interface method with a value receiver using a pointer will automatically dereference that pointer
and
a reference to a non-interface method with a pointer receiver using an addressable value will automatically take the address of that value
This is why obj.Method() works whether obj is an *SA or an SA.
Hope that helps.