Object containing a map?

Question

I'm trying to get a list of all of our endpoints.

We use Goa.

I noticed that we add all of our endpoints to a service (goa.New("service_name")). I also realized that if I print service.Mux I can see all the endpoints. However, the endpoints look like they are in a Map, which is contained by an object. When printing service.Mux, I see memory addresses as well. How do I get just the endpoints alone?

fmt.Println("Service Mux: ", service.Mux)

&{0xc42092c640 map[OPTIONS/api/my/endpoint/:endpointID/relationships/links:0x77d370 ...]}

It seems like an struct. Please provide [Minimal, Complete, and Verifiable](https://stackoverflow.com/help/mcve) example to produce a problem you are facing. — Himanshu, Jun 20 '18 at 12:34
@Himanshu what other minimal, complete and verifiable information do I need to add? As mentioned service comes from a library called Goa: https://goa.design/implement/mux/ — BigBug, Jun 20 '18 at 12:40
just post the code you have tried and proper output of log and the struct of `service.Mux` — Himanshu, Jun 20 '18 at 12:41
@Himanshu i have printed how to create a new service, i have printed the println for printing the service and i have printed the output above.... not too sure what i am missing? — BigBug, Jun 20 '18 at 12:58
Just look up the documentation of Mux and use whatever suitable fileds or methods or functions it offers. — Volker, Jun 20 '18 at 14:17

score 2 · Accepted Answer · answered Jun 20 '18 at 20:17

You could use the reflect and unsafe packages to get to the underlying and unexported map value, which is defined here (https://github.com/goadesign/goa/blob/master/mux.go#L48).

Something like this:

rv := reflect.ValueOf(service.Mux).Elem()
rf := rv.FieldByName("handles")
rf = reflect.NewAt(rf.Type(), unsafe.Pointer(rf.UnsafeAddr())).Elem()

handles := rf.Interface().(map[string]goa.MuxHandler)
for k, h := range handles {
    fmt.Println(k, h)
}

But do note, that with this approach your code depends on an implementation detail as opposed to a public API, and therefore you cannot rely on its stability.

score 0 · Answer 2 · answered Jun 20 '18 at 14:51

0

Goa library currently does not support this. Mux is an interface that has very few options available. Among the options available there is not one for retrieving that map unfortunately :-(

answered Jun 20 '18 at 14:51

BigBug

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You can use the `reflect` package to get to the [map](https://github.com/goadesign/goa/blob/master/mux.go#L48). E.g. https://play.golang.org/p/KiLSqDDTWVA – mkopriva Jun 20 '18 at 15:20
@mkopriva can you make this an answer so i can select it? – BigBug Jun 20 '18 at 20:09

Object containing a map?

2 Answers2