I once wrote an article on Medium about dependency injection - Dependency Injection is not Scary!. Recently joined dev.to, I thought I'd bring my thoughts here as well.
Okay Eli, I know how to dependency inject now thanks to the medium article. BUT WHEN DO USE IT?
Bear with me here, I'll get to that soon. Currently building an inbox feature, I needed a form object for creating the conversation AND responding/editing the conversation.
What I could have done was create a form object, wipe my hands clean and be done with it. Or I could also make this form reusable in other controllers. 🤓
module Inbox
class ConversationForm < BaseForm
attr_reader :conversation, :message, :sender
def initialize(conversation, params = {})
@conversation = conversation
@sender = build_sender
@message = conversation.messages.build(user: @sender)
end
...
end
end
But making use of dependency injection, I was able to reuse the form for another controller.
module Inbox
class ConversationForm < BaseForm
attr_reader :conversation, :message, :sender
def self.build(params={})
conversation = Conversation.new
sender = build_sender
new(conversation, sender, params)
end
def initialize(conversation, sender, params = {})
@conversation = conversation
@sender = sender
@message = converation.messages.build(sender: sender)
end
...
end
end
I would use Inbox::ConversationForm.build when I want to create a new conversation. In another controller/action, I would predefine the conversation and inject it into the form.
# ConversationsController
# Creating a Conversation
def new
@form = Inbox::ConversationForm.build
end
# My::ConversationsController
def new
@form = Inbox::ConversationForm.new(fetch_conversation, Current.user)
end
# BOTH
def create/update
if @form.save
render :new
else
redirect_to some_path
end
end
private
def fetch_conversation
Inbox::Conversation.find(params[:conversation_id])
end
Once again, go forth and Dependency Inject!
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