Go: What is the difference between pointer and value receiver?

Pointer receiver (*T) — method receives *T, can modify the original value, avoids copying. Value receiver (T) — method receives T, works on a copy, cannot affect the original.

The choice affects mutability, performance, and interface satisfaction. If you define even one method with a pointer receiver, Go encourages making all methods on that type use pointer receivers for consistency.

1type Counter struct {
2    n int
3}
4
5// Pointer receiver — modifies the original
6func (c *Counter) Inc() {
7    c.n++
8}
9
10// Value receiver — read-only
11func (c Counter) Value() int {
12    return c.n
13}
14
15var c Counter
16c.Inc()
17c.Inc()
18fmt.Println(c.Value())  // 2

Performance: Value receivers copy the entire struct. For small structs (one or two fields) this is negligible. For large structs, pointer receivers avoid the copy.

When to use:

• Pointer — when the method mutates the receiver, or the struct is large.
• Value — when the method is read-only and the struct is small.

Common mistakes:

• Mixing receiver types within one type — leads to confusion.
• Using a value receiver on a method that needs to modify the struct — silent data loss.
• Passing a value type to an interface that expects a pointer receiver method.
• Forgetting that methods with value receivers don't work well with nil receivers.