Hi all,
I need some guidance whether what I want to do is somehow possible in Go.
I've already searched answers for two days. My problem boils down to how to
sneak more in a type without changing the type.
Lets say I have to implement the following method:
*func (s *server) Get(ctx context.Context, request *generated.Request)
(*generated.Response, error) { var response generated.Request return
&response, nil*
*}*
In this case it is a zero value (nil) that will be returned for response
but that is not the problem - I am just marking the types
I want to return a response that somehow implements a wider interface than
generated.Response
Since that object is generated source, I cannot change it or add methods to
it, however I can do the following:
*// Declare a new type that embeds the generated.Responsetype
EnrichedResponse generated.Response// Add a method that depends only on
rfunc (r *EnrichedResponse) Enriched() int { return r.foo + 42}// Return
the enriched responsefunc (h *handler) Get(ctx context.Context, request
*generated.Request) (*generated.Response, error) { var enriched
EnrichedResponse response := generated.Response(enriched) return
&response, nil}*
My problem is the *Enriched() *method - it can only use the state available
in the initial *generated.Response* and I need more in order to implement
the functionality.
I cannot just make *EnrichedResponse* a struct embedding
*generated.Response *and add more state because then I cannot do the
conversion from normal response to enriched.
So here is my question - is there any way to have this state somewhere so
that the Enriched() method does not take more arguments but can be called
directly.
A method declaration in Go is quite static. Additional state can be kept in
some kind of closure but then I have no idea how to glue that closure to
the method.
Is there any trick I am missing?
-----
Why would I want to do this? What am I trying to achieve?
Basically there is a lot of generated code and I want to keep compatibility
with it.
Similar to the way Go embeds wider interfaces into narrower ones I want to
be able to add methods to the generated code without having to change it.
Then - whenever some code calls the *Get* method on the server - based on
the whether the returned value implements the *Enriched* interface or not
and the value it returns - I can dispatch behavior.
Kind regards:
al_shopov
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