When to create classes for dependency injection about oclif HOT 7 CLOSED

@Junkern I'm a product manager at Heroku where we've been developing oclif. As we're just getting started with the project, I'd be really interested in your feedback and learning more about your use case. Feel free to respond here or drop us a note at [email protected]

from oclif.

by design we do not call any files so we only load the files we need. In a large project, it might take several seconds to create everything.

It sounds like you want an init hook. We should have some docs and a generator for that soon, but for now here is what you need to do:

First add a line like this to declare the hook: https://github.com/heroku/cli/blob/oclif/package.json#L56

(You will want init probably for your usage though, prerun happens later)

Then create a hook file like this: https://github.com/heroku/cli/blob/oclif/src/hooks/prerun/analytics.ts

You can also create your own hooks

from oclif.

reading your message again though, I would probably use a base class here. Init hooks are more for things you want to run on every command. It would work, but you'd likely have to involve some globals. Unfortunately I don't have a great example of setting this up, but I would do something like this:

class MyBaseClass extends Command {
  myApiClient = new ApiClient()
}

then in the command:

class extends MyBaseClass {
  async run() {
    this.myApiClient.doSomething()
  }
}

Which does not give you dependency injection though. Maybe https://github.com/thlorenz/proxyquire would be helpful?

from oclif.

A third idea:

class MyBaseClass extends Command {
  static apiClient = ApiClient
  myApiClient = new MyBaseClass.apiClient()
}

and in the test:

beforeEach(() => {
  MyBaseClass.apiClient = MockApiClient
})

Hopefully one of these ideas is helpful. Let me know if you have any ideas how else this might be done!

from oclif.

Thanks for the quick feedback!

I indeed went for the base class scenario. But instead of doing that with static, I simply but the initialization of the classes I need in all commands into the init() function. It worked, but I don't know if there are any downsides^^ Just tested it out with static and that works as well.

from oclif.

so long as you don't need to modify the static property in the test then doing it as an instance property should be fine. The advantage of static is you have access to it in the test if you want to modify it

from oclif.

That makes totally sense! Thanks a lot:)

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