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 Point struct{ X, Y float64 }
2
3func (p Point) DistanceTo(q Point) float64 {
4    dx := p.X - q.X
5    dy := p.Y - q.Y
6    return math.Sqrt(dx*dx + dy*dy)
7}

When to use:

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

Common mistakes:

• Mixing receiver types within one type — causes confusion.
• Value receiver when mutation is needed — silent data loss.
• Not understanding that a value receiver on a nil pointer still works (it receives a copy of nil).
• Choosing value for a struct with embedded slices — the slice header is copied, but the underlying array is shared.