Hotwire and Service Objects in Rails 7
If you are reading this blog post, I am going to assume some level of familiarity with Ruby on Rails v7 and some of the new tooling that it provides, specifically the “Hotwire” stack of Turbo, Turbo Frames, Turbo Streams, and Stimulus. I’ve been using it at work lately and have not felt this excited about web development technologies since I first started learning Rails oh so many years ago. It is an exciting time to be a Rails developer!
So, on to the point of this particular article… If Google brought you here, it is fair to say that you are bearing witness to some very unexpected behavior between your instance variables, the service objects / service classes you are calling in on them in your controllers, and the partials that are getting rendered as an end result.
In fact, you might think something is wrong with your hotwire implementation until you look at the Turbo Stream HTML response in your browser Inspector’s Network tab, where you may be very surprised to see that attributes you expected to see updated are not being updated at all!
This issue happened to me and after chasing it down, realized that I was passing in the objects ID into the service object, and not the object itself. That means that the object I was mutating in the service class is not the same object in memory as the object I had access to in the controller, so sending it along to be rendered displayed no updates. Keep in mind that previously we were not displaying real-time updates on the webpage (In fact, the page and the object would both be reloaded upon controller actions being triggered) so this Service Class ID vs Object issue never surfaced until we added real-timeish Hotwire into the mix.
The solution to this issue is to either refactor your service class to accept the object rather than an ID (so that you are now performing operations on the exact same object throughout the entirety of this controller action), or, to reassign the mutated widget (the payload) back to the widget instance variable after it exits the service, as seen below…
def set_as_primary
authorize(Widget)
result = WidgetUpdaterService.call(widget_id: @widget.id)
if result[:success?]
flash.now[:success] = t('controllers.widgets.widgets_updated')
else
flash.now[:notice] = t('controllers.widgets.something_went_wrong')
end
<!-- pay attention to the line below -->
@widget = result[:payload]
<!-- pay attention to the line above -->
render turbo_stream:
[
turbo_stream.update('is_primary', partial: 'admin/shared/tables/widget_row', locals: { variable: @widget.is_primary? }),
turbo_stream.update('flash', partial: 'shared/flash')
]
end
PS If all else fails and you are desperate, you could call reload on your object in the controller after the service, but before the render, but the way above is a more elegant solution to the issue.