Does dereferencing a struct return a new copy of struct?
tl;dr Dereferencing (using the *
operator) in Go does not make a copy. It returns the value the pointer points to.
No, "assignment" always creates a copy in Go, including assignment to function and method arguments. The statement obj := *p
copies the value of *p
to obj
.
If you change the statement p.color = "purple"
to (*p).color = "purple"
you will get the same output, because dereferencing p
itself does not create a copy.
When you write
obj := *p
You are copying the value of struct pointed to by p
(*
dereferences p
). It is similar to:
var obj me = *p
So obj
is a new variable of type me
, being initialized to the value of *p
. This causes obj
to have a different memory address.
Note that obj
if of type me
, while p
is of type *me
. But they are separate values. Changing a value of a field of obj
will not affect the value of that field in p
(unless the me
struct has a reference type in it as a field, i.e. slice, map or channels. See here and here.). If you want to bring about that effect, use:
obj := p
// equivalent to: var obj *me = p
Now obj
points to the same object as p
. They still have different addresses themselves, but hold within them the same address of the actual me
object.