Blog / Go Language Spec

Method receiver base types

August 25, 2023

There’s a lot to unpack about method receiver types, so we’ll do it over two days.

Method declarations

…

The receiver is specified via an extra parameter section preceding the method name. That parameter section must declare a single non-variadic parameter, the receiver.

This bit is fairly straight forward. The receiver is specified in an extra parameter section preceeding the method name:

func (reciever ReceiverType) MethodName(/* 0 or more regular arguments */) { /* ... */}

Futher, only a single argument is allowed, and it may not be variadic. In other words, there can be only a single receiver for a method.

func (receiver1 ReceiverType, receiver2 Othertype) Method() {} // Invalid

func (receivers ...ReceiverType) Method() {} // Invalid

Its type must be a defined type T or a pointer to a defined type T, possibly followed by a list of type parameter names [P1, P2, …] enclosed in square brackets.

So we can define methods on generic types… we’ll see how that works in detail soon.

T is called the receiver base type.

There we have it. The type of the receiver argument is the base type of the method.

func (r Receiver) Method1() // Method1's base type is Receiver

func (r *Receiver) Method2() // Method2's base type is *Receiver

Quotes from The Go Programming Language Specification Version of August 2, 2023

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