majiayu000 Pointer Receiver Nil
Problem
Methods with pointer receivers can be called on nil. Must handle nil receiver.
Pattern
WRONG - Assume receiver is non-nil
type Tree struct {
Value int
Left *Tree
}
func (t *Tree) Sum() int {
return t.Value + t.Left.Sum() // PANIC if t or t.Left is nil
}
CORRECT - Handle nil receiver
type Tree struct {
Value int
Left *Tree
Right *Tree
}
func (t *Tree) Sum() int {
if t == nil {
return 0 // Nil tree has sum of 0
}
return t.Value + t.Left.Sum() + t.Right.Sum()
}
// Now safe to call
var tree *Tree // nil
sum := tree.Sum() // Returns 0, no panic
Use Cases
Nil receiver pattern enables elegant recursive algorithms and optional behavior.
Quick Fix
- Check if receiver is nil at method start
- Define sensible zero behavior for nil receiver
- Document whether methods are nil-safe
When NOT to Use
If nil receiver doesn't make semantic sense, panic early with clear message.