Rails%203%20In%20Action

Adding more posts to topics
really simple. When a post is created, Rails will check for any associations with the
counter_cache option set to true. It then gets the current count for this association,
adds 1 to it, and saves the associated object. When a post is deleted, it will do the same
thing, except instead of adding 1, it will subtract 1. This way, you’re always going to
have an accurate count of the number of posts each topic has.
In the app/views/forem/topics/index.html.erb file now, you’ll change this line
to this:
Rather than inefficiently calling posts.count for each topic, Rails will now reference
the posts_count attribute for the Forem::Topic object instead, saving you many queries
for the index action when you have many topics. This also means that you’ll have
an accurate count of posts for your topics!
You’ll commit this change now:
git add .
git commit -m "Add posts counter cache to topics"
You’ve fixed up one of the placeholder lines in the app/views/topics/index.html.erb
view now, and when you get around to adding users to your engine, you’ll fix up the
second placeholder line.
In this section, you’ve created an interface for creating topics and their first post,
which is the first feature of your engine and a well-tested one at that. You’ve seen how
to use fields_for to yet again create nested resources. You first saw that back in chapter
8. You’ve also seen the :counter_cache option for belongs_to that you can use to
cache the count of an association, so that you don’t have to perform another query to
get that number. That’s a potential lifesaver if you’re displaying a lot of objects at once
and want to know an association’s count on all of them, like in your topics view.
In the next section, you’re going to add the ability to add posts to a topic, because
what are topics without posts?
17.6 Adding more posts to topics
A forum system without a way for users to reply to topics is nearly useless. The whole
point of having topics is so that users can reply to them and keep the topic of conversation
going for as long as they wish!
The feature that you’re about to develop will let people add these replies to existing
topics. They’ll click a New Reply link on a topic, fill in the post text, and click the
submit button. They should then see their post within the list of posts in the topic.
Simple, really!
You’ll also see here more examples of integration testing with Capybara; you’ll
repeat some of the concepts, but it’s a good way of learning.
You’ll start out with a new spec file called spec/integration/posts_spec.rb and begin
to fill it with the content from the following listing.
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