Define method of struct inside function

Question

I have this code

func baz() {
    type mockDatabase struct{}

    //
    //  More code
    //
}

I want to define a method of mockDatabase, so the full code would look like this:

func baz() {
    type mockDatabase struct{}

    func (m *mockDatabase) Foo() {
        // Implement function here
    }

    //
    //  More code
    //
}

The reason I want to do this is I'm injecting a dependency into a function, and I want to create a "mock object" to inject into the function (the function takes an interface as an argument and the mock object will implement the interface).

I could create the struct outside, but it seems more logical to declare the struct locally to decrease namespace clutter, especially when these mock objects will only be used once. Am I missing something here? Is it better practice to define it outside the test function so it's not long? What should I do here?

Answer 1

The idiomatic Go would be to use package for namespacing.

package mock 

type MockDatabase struct {}

func (m *mockDatabase) Foo() {}

In the main code, you can call from the package

package main

import (
        "path/to/mock"
)

var m = New(mock.MockDatabase)

func baz() {
        m.Foo()
}