Dear Gophers!
I was wonder if it possible to force immutability on the method receiver? I
know Go doesn't support immutable types and that it is possible to pass the
receiver by value but if the receiver struct has a field with a pointer
type the method may still manipulate it:
type Counter struct {
n *int
}
func (c Counter) Render() string {
*c.n += 1
return strconv.Itoa(*c.n)
}
I would like to force (or hint) the the user in writing interface{ Render()
string } implementations that don't manipulate the method receiver. So that
they can be considered 'pure' in the functional sense of the word and can
be called repeatedly without side effects. I would like the user to be able
to define implementations of interface{ Render() string }such that I can
safely call the method and use the returned string to write a http.Reponse
without
it changing between requests.
I control the way in which Render is called and I am open to crazy answers
such as:
- Maybe it is possible to use reflect to "switch" out the value receiver
for a temporary value which is discarded after every call?
- Maybe i can use static code analysis to warn the user? How feasible is it
to prevent all cases of this happening with just static code analysis? can
this be done at runtime?
- I could instead ask the user to provide a factory function that init new
Counters but maybe very inefficient if the structs are very large (or have
many nested structs)?
Or maybe there is some possibility that I'm missing?
Cheers,
Ad
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