go wire, wiring up the dependencies

Question

I am using Google wire to wire up the dependencies in one of my Go projects. So far all the dependencies were wired up successfully.

I have following container:

type Container struct {
    Logger               logger.StructuredLogger
    IDGenerator          idgenerator.IDGenerator
    Arango               arangodb.Arango
}

Here StructuredLogger , IDGenerator and Arango are interface.

The container set is defined as below:

var mockContainerSet = wire.NewSet(
    Container{},
    ResolveStructuredLogger,
    ResolveIDGenerator,
    ResolveArangoDB,
)

Functions:

func ResolveStructuredLogger() logger.StructuredLogger {
    panic(wire.Build(wire.InterfaceValue(new(logger.StructuredLogger), logrusprovider.NewLogrusLogger(nil))))
}

func ResolveIDGenerator() idgenerator.IDGenerator {
    panic(wire.Build(wire.InterfaceValue(new(idgenerator.IDGenerator), examples.NewKSUIDGenerator())))
}

Now the issue is when I want to create a provider for Arango . The factory method for Arango provider is taking IDGenerator as an argument.

func NewMockedArango(generator idgenerator.IDGenerator) (*MockedArango, error){
    if generator == nil {
        return nil , errors.New("mock arangodb expects a valid IDGenerator")
    }
    return &MockedArango{generator:generator}, nil
}

All the functions from arangodb.Arango is implemented. And I tried the following to create a provider:

func ResolveMockArangoDB(idGenerator idgenerator.IDGenerator) (arangodb.Arango, error) {
    panic(wire.Build(wire.InterfaceValue(new(arangodb.Arango), mockdb.NewMockedArango(idGenerator))))
}

But the wire is throwing errors, I tried a lot of ways and no success to set this up. Any help?

Error:

2-valued mockdb.NewMockedArango(idGenerator) (value of type (*github.com/tejashwi/catalog-manager-svc/pkg/webservice/arangodb/mockdb.MockedArango, error)) where single value is expected

Answer 1

Signature of wire.Interface is InterfaceValue(typ interface{}, x interface{})

Here you need to pass two single-valued arguments. In the second argument, you are passing 2-valued argument since function mockdb.NewMockedArango is returning 2 values.

You can change function ResolveMockArangoDB to:

func ResolveMockArangoDB(idGenerator idgenerator.IDGenerator) (arangodb.Arango, error) {
    mockedArango, err := mockdb.NewMockedArango(idGenerator)
    <HANDLE err>
    panic(wire.Build(wire.InterfaceValue(new(arangodb.Arango), mockedArango)))
}