Can Go Methods with Pointer Receivers Be Called on Non-Pointer Variables?

Can Methods of Pointer Types Be Called on Simple Types in Go?

Despite the Go specification stating that the method set for T includes the methods of T, confusion arises about whether methods with T receivers can be invoked on variables of type T.

Method Invocation

The crux of the matter is that method calls are not restricted to using the pointer receiver type. The compiler cleverly handles method invocations by automatically dereferencing the value to obtain the desired receiver type. In effect, calls to methods with *T receivers are equivalent to calls on (&user).m(), where &user retrieves the address of the variable.

Practical Demonstration

Consider the following code example:

package main

import "fmt"

type User struct{}

func (self *User) SayWat() {
  fmt.Println(self)
  fmt.Println(reflect.TypeOf(self))
  fmt.Println("WAT\n")
}

func main() {
  var user User
  user.SayWat()
}

Upon running this code, you'll notice that the method is executed successfully, even though user is not of pointer type. This is because the compiler automatically dereferences user to call the SayWat method.

Addressing Ambiguity

A definite distinction emerges when dealing with method returns. If a method returns a value, it creates an unaddressable result, which cannot be invoked directly with the dot syntax. Instead, use the "&" syntax explicitly to obtain the address of the return value.

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