Rendering components outside of view context

[dennyf]

I'm trying to find if there is a way to render a component outside of the view context. I'm working on a feature to register a custom tag in my markdown processor - so basically, I want to replace the custom tag/shortcode with the markup generated by a component.
So, I'm wondering if there is a way to call the component to generate the markup from another class, outside the view context?
Thanks!

[dylnclrk]

Not sure if I understand correctly, and maybe this is too hacky, but could you set up a fake view context in much the same way that render_inline does?

[joelhawksley]

@dennyf - @dylnclrk is probably on the right track.

I'd love to see a PR for this. Let me know if you'd like to pair program on it 😄

[dennyf]

@dylnclrk @joelhawksley Thank you both! I did something similar too, the following code worked fine for a very simple component :

component = MyComponent.new(title: "My Component")
component.render_in(ActionView::Base.new)

but it felt too hacky and probably it's not a good idea to call render_in directly.
I'll dig into the ActionView Component code to better understand how it works internally - I'll submit a PR if I can get to find a good way to implement this.

[joelhawksley]

@dennyf render_in is the public interface for components - it's definitely the right way in!

What if we had changed render_in from:

def render_in(view_context, *args, &block)

to:

def render_in(view_context = ActionView::Base.new, *args, &block)

I'm not sure if that would work in all cases, but I think we'd be fine to use that kind of fallback.

[dennyf]

@joelhawksley Thanks, that's good to hear! Actually I just noticed that Rails is throwing a warning when initializing ActionView::Base with no arguments:

DEPRECATION WARNING: ActionView::Base instances should be constructed with a lookup context, assignments, and a controller.

so I guess it won't be as simple as that, I think it will be an overkill to initialize it with all the required parameters... I'll see if I can get any other ideas.

[joelhawksley]

@dennyf It might be possible to provide all of those things, FWIW. Let me know if you want to have a look at this together: joelhawksley@github.com

[dennyf]

@joelhawksley Sorry for the late reply - my schedule is very ovestretched these days - the best I can do is spend a few minutes here and there when I get any free time. So can we continue the discussion here in this issue? In this way I can be more flexible with my time.

As for providing all the options - I noticed that at this point view_context is the only parameter that's actually required (although the warning also says that assignments and controller are needed), basically the following works fine without causing any warnings:

component = MyComponent.new(title: param)
# not sure if that's the best way to create a lookup context
lookup_context = ActionView::LookupContext.new(ActionController::Base.view_paths)
view = ActionView::Base.new(lookup_context, {})
component.render_in(view)

so technically it should be okay to go without passing a controller instance for now... or do you think it's better to pass a controller as well in case things change in the future?

[pinzonjulian]

Hi everyone
I'm looking into caching (#42 & #234 ) and my research (still in early stages) is pointing me towards LookupContext too. Do you guys know enough about it? I could use a quick lesson on it if you have the time.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ramontayag]

This doesn't work in 2.40.0 when helpers are used:

NoMethodError: undefined method `view_context' for nil:NilClass

   13  module ViewComponent
   14    class Base < ActionView::Base
  181      def helpers
  182        if view_context.nil?
  191        end
❯ 193        @__vc_helpers ||= controller.view_context
  194      end
  524    end
  525  end

[boardfish]

@ramontayag Use of helpers means that your component is coupled to the view context. You could consider including the helpers directly on the component class so that it's decoupled from the view context. Alternatively, Joel's solution might work for you.