You can certainly do what, I think, you're wanting to do. "var versions
map[string]Version" is valid. You probably want a package entry point
something like "GetVersion(s string) *Version" to select the one you want
to use in your mainline. (Note: each Version can use a unique struct if
necessary.)
On Thursday, December 14, 2017 at 7:20:05 PM UTC-7, jakdept wrote:
>
> I'm writing a utility to import/export data into an API. I'd like to be
> able to accept multiple input/output formats, and support multiple
> commands. I was going to use kingpin for the flags/commands, and do a type
> format after that.
>
> My plan was to declare an interface with the methods I'm going to use, a
> struct that's got the parameters needed for the interface, but doesn't
> satisfy it, and declare a map of structs that do satisfy that interface.
>
> type versionParams struct {
> options int
> sess api.Session
> in io.ReadCloser
> out io.WriteCloser
> log *log.Logger
> }
>
>
> type Version interface {
> Import()
> Export()
> Example()
> }
>
>
> var versions map[string]Version
>
> In main, I'd detect the actions, and if it's one of the actions for one of
> those types, create the object, load it up with input and output and stuff.
> Note, because of the flags I'm using, *format is a pointer to a string
> holding the format's name. So, I was thinking I'd do something like:
>
> args := versionParams{}
>
>
> // some stuff to fill in the args
>
>
> args.(versions[*format]).Import()
>
> Then, for each version I want to add, in that version I'd do something
> like the following, in it's own file:
>
> type v1csv struct {
> versionParams
> Version
> }
>
>
> func init() {
> versions["v1csv"] = v1csv
> }
>
>
> func (v *v1csv) Import() {
> // do stuff
> }
>
>
> func (v *v1csv) Example() {
> // do stuff
> }
>
>
> func (v *v1csv) Export() {
> // do stuff
> }
>
> I don't think this works for multiple reasons though. I don't think you
> can declare a map of types that satisfy an interface like that? And once
> you do, I guess I don't know if I can cast/convert from one struct to
> another without directly naming the struct...? I guess I could drop the
> generic versionParams struct and just create structs for each type, but I
> would still want to put those struct types into a map - that's the part
> that I'm stuck on figuring out.
>
> I wanted to go with something like this layout specifically so that I
> could add new formats by simply adding that one format in a self contained
> file. I don't want to statically name them and
>
> Mostly, I think I'm just lost in design and I cannot see the way out
> myself. Any suggestions to help me figure out how to do this, or something
> more appropriate, would be appreciated. :-)
>
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