I've read a Tour of Go and Effective Go, http://golang.org/doc/effective_go.html#pointers_vs_values, but still have a difficult time understanding when you would define a method on a struct using a value method receiver instead of a pointer method receiver. In other words, when would this:
type ByteSlice []byte
func (slice ByteSlice) Append(data []byte) []byte {
}
be preferable over this?
func (p *ByteSlice) Append(data []byte) {
slice := *p
*p = slice
}
分享 Slices are one place where it's not always obvious at first. The Slice header is small, so copying it is cheap, and the underlying array is referenced via a pointer, so you can manipulate the contents of a slice with a value receiver. You can see this in the sort package, where the methods for the sortable types are defined without pointers.
The only time you need to use a pointer with a slice, is if you're going to manipulate the slice header, which means changing the length or capacity. For an Append method, you would want:
func (p *ByteSlice) Append(data []byte) {
*p = append(*p, data...)
}
