Detailed explanation of the differences between the recipients of general methods and interface methods

In Go language, there is a certain difference between the receiver of the general method and the receiver of the interface method.

• In general

If the defined receiver is a value, it can be called using a value or a pointer;

If the defined receiver is a pointer, it can be called using a value or a pointer.

• In the interface method

If the defined receiver is a value, it can be called with either an interface value or an interface pointer;

If the defined receiver is a pointer, it can only be called with an interface pointer, not with an interface value.

As shown in the following example:

package main

import "fmt"

type T struct {
    S string
}

type I interface {
    A()
    B()
}

func (t T) A() {
    ()
}

func (t *T) B() {
    ()
}

func main() {
    t := T{"normal method"}
    pt := &t
    ()
    ()
    ()
    ()

    //var i I = T{"interface method"}
    var i I = &T{"interface method"}
    ()
    ()
}

If used
var i I = &T{"interface method"}Then it can be executed.

If used
var i I = T{"interface method"}An error is reported:

./:30:6: cannot use T{...} (type T) as type I in assignment:
    T does not implement I (B method has pointer receiver)

It prompts that method B uses the pointer receiver and cannot be called by the interface value.

So, why is there such a difference? For more information about the differences between different recipients of Go methods, please follow my other related articles!