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

Pointer receiver (*T) — method operates on original, can modify, avoids copy. Value receiver (T) — method operates on copy, changes discarded.

Pointer receivers are necessary for mutation. They also avoid copying large structs.

1type Stack struct {
2    items []interface{}
3}
4
5func (s *Stack) Push(item interface{}) {
6    s.items = append(s.items, item)
7}
8
9func (s *Stack) Pop() (interface{}, bool) {
10    if len(s.items) == 0 {
11        return nil, false
12    }
13    item := s.items[len(s.items)-1]
14    s.items = s.items[:len(s.items)-1]
15    return item, true
16}

When to use:

• Pointer — mutation, large structs, interface impl.
• Value — small structs, read-only.

Common mistakes:

• Mixing receiver types.
• Value receiver for mutation — silent data loss.
• Nil pointer dereference.
• Value on struct with slices.