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

Pointer receiver (*T) — method operates on the original via pointer, can modify it, avoids copy overhead. Value receiver (T) — method operates on a copy, changes are discarded.

The choice affects whether the method has side effects. Pointer receivers are the only way to mutate a receiver's fields from within a method.

1type Balance struct {
2    amount float64
3}
4
5func (b *Balance) Deposit(amt float64) {
6    b.amount += amt  // modifies original
7}
8
9func (b Balance) String() string {
10    return fmt.Sprintf("$%.2f", b.amount)
11}
12
13b := Balance{100}
14b.Deposit(50)
15fmt.Println(b)  // $150.00

When to use:

• Pointer — mutation needed, large structs, interface implementation.
• Value — small structs, read-only, immutable semantics.

Common mistakes:

• Mixing receiver types within one type — inconsistent behavior.
• Value receiver for mutating method — silent data loss.
• Nil pointer receiver dereference — must check before accessing fields.
• Value receiver on struct with embedded slices — copies slice header but shares backing array.