Why Does Go Use Pass by Value for Receivers?

Go Receivers: Understanding Pass by Value

Contrary to intuition, Go receivers are passed by value, raising the question of why this is so given the apparent benefits of pass by reference.

Pass by Value in Go

The answer lies in the fundamental design of Go, where everything is passed by value. This ensures consistency across the language, eliminating the need to distinguish between pass by value and pass by reference scenarios.

Receiver as an Argument

When defining a method on a type, the receiver (e.g., s in func (s *MyStruct) pointerMethod()) behaves like an argument to that method. Choosing between a value or pointer receiver is analogous to deciding whether a function argument should be a value or a pointer.

Considerations for Pointer Receivers

If the method needs to modify the receiver (e.g., changing fields of s), a pointer receiver (as in pointerMethod) must be used. Otherwise, the modifications would not be visible to the caller (as in valueMethod).

Efficiency and Consistency

Using a pointer receiver can improve efficiency if the receiver is large. Consistency should also be considered: if some methods require pointer receivers, all methods on the type should use pointer receivers to maintain a consistent method set.

Value Receivers for Efficiency and Simplicity

For small types like basic types, slices, and small structs, value receivers are efficient and easy to understand. They are the preferred choice unless the method semantics require a pointer receiver.

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