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

Pointer receiver (*T) — receives a pointer to the value, can modify the original, avoids copying. Value receiver (T) — receives a copy, changes don't affect the original.

Pointer receivers are necessary when a method needs to mutate the receiver's state. They're also preferred for large structs to avoid the cost of copying.

1type Queue struct {
2    items []string
3}
4
5// Pointer receiver — mutates the queue
6func (q *Queue) Push(item string) {
7    q.items = append(q.items, item)
8}
9
10func (q *Queue) Pop() (string, bool) {
11    if len(q.items) == 0 {
12        return "", false
13    }
14    item := q.items[0]
15    q.items = q.items[1:]
16    return item, true
17}

Value receivers are appropriate for small, immutable types where copying is trivial and you want read-only semantics.

1type Color struct{ R, G, B uint8 }
2
3func (c Color) Hex() string {
4    return fmt.Sprintf("#%02x%02x%02x", c.R, c.G, c.B)
5}

When to use:

• Pointer — mutation needed, large structs, implementing interfaces with pointer receivers.
• Value — small structs (1-2 fields), read-only methods, immutable semantics.

Common mistakes:

• Mixing receiver types within one type — choose one and stick with it.
• Value receiver on a method that mutates — the caller sees no change, silent bug.
• Nil pointer receiver dereference — must check before accessing fields.
• Value receiver on a struct with embedded slices — copies the slice header but shares the underlying array.