I'm writing a wrapper to map with some additional functionality I need. Some of the most important things is the ability to marshal and unmarshal the data while retaining genericity. I managed to write an marshaller using the encoding/gob encoder, but since it would be nice if the marshalled data was human readable, I decided to code another implementation with JSON.
I got gob to encode from and decode to generic interface variables neatly by passing it a implementation object instance with Register(). (This resource helped me with the details! http://www.funcmain.com/gob_encoding_an_interface)
However, JSON doesn't have Register(). Let's say we have a value of type
type ConcreteImplementation struct {
FieldA string
FieldB string
}
func (c ConcreteImplementation) Key() string {
return c.FieldA // ConcreteImplementation implements genericValue
}
in a variable of type
type genericValue interface {
Key() string
}
When I marshal that, it outputs JSON like this:
{"FieldA":"foo","FieldB":"bar"}
And when I try to unmarshal that again into a variable of type genericValue, it says:
panic: interface conversion: map[string]interface {} is not genericValue: missing method Key EDIT: Oops, actually it says this!
Error with decoding! json: cannot unmarshal object into Go value of genericValue
Quite obviously, it tries to marshal the data like it says here: http://blog.golang.org/json-and-go (See 'Generic JSON with interface{}')
How can I get it to try to fit the data to an specific implementation, like gob decoder would try if the implementation is Register()ed? Register() was godsend, it allowed to marshal and unmarshal generically like it was nothing. How do I get JSON to do the same thing?
