I’d like to start with a question: Have you ever seen code like this?
class User
I have. But what few developers know is that many methods in Active Record already accept a block, so you don't need to invoke tap
in the first place. And that's all because Active Record loves blocks! Let's go through some examples.
Using blocks with Active Record
When creating an Active Record object, either by using new
or create
/create!
, you can give a block straight to the method call instead of relying on tap
:
User.new do |user|
user.name = "John Doe"
user.username = "john.doe"
user.password = "john123"
end
User.create do |user|
user.name = "John Doe"
user.username = "john.doe"
user.password = "john123"
end
And you can mix and match with hash initialization:
User.new(name: "John Doe") do |user|
user.username = "john.doe"
user.password = "john123"
end
All these methods, when receiving a block, yield
the current object to the block so that you can do whatever you want with it. It's basically the same effect as using tap
. And it all happens after the attributes hash have been assigned and other internal Active Record code has been run during the object initialization, except by the after_initialize
callbacks.
That's neat. That means we can stop using tap
in a few places now. But wait, there's more.
Active Record associations also love blocks
We talked about using blocks when building an Active Record object using new
or create
, but associations like belongs_to
or has_many
also work with that, when calling build
or create
on them:
class User
That's even better. That means we can stop using tap
in a few more places.
Wrapping up: Active Record <3 blocks
It is possible to avoid extra work, sometimes simple stuff such as using tap
with methods like new
and create
, other times more complicated ones, by getting to know what the framework can give us for free.
There are other places inside Active Record that accept blocks, for instance first_or_initialize
and friends will execute the given block when the record is not found, to initialize the new one.
In short, next time you need a block when creating records using Active Record, take a minute to see if you can avoid using tap
by using an already existing feature. Remember: Active Record <3 blocks. And don't do that with blocks only, the main idea here is that you can learn more about the framework, and let it do more work for you.
How about you, do you have any small trick in Ruby or Rails that makes your work easier? Take a minute to share it with others in the comments. 🙂
yet another good example about scoping
Developer.where(“salary = 9000”).scoping do
Developer.where(“name = ‘Jamis'”).first
end
Awesome!!!
Nice, thanks for sharing.
Here’s how I tested the above: http://pivotallabs.com/users/rclutton/blog/articles/2203-testing-within-an-activerecord-block
Cool, didn’t know that. Thanks Charles!
thanks for sharing! I used the tap method all the time, now can write less code!
would one find it mentioned in the docs anywhere that these methods take blocks? How’d you figure it out? If I remember in the future “oh yeah, some AR methods take blocks but I forget which ones and how”, is there a way to look this up in the docs, or am I reduced to googling for your blog post?
Some of these methods are documented inside the Active Record API, like here: http://api.rubyonrails.org/classes/ActiveRecord/Base.html, but I’m afraid not all possibilites are covered – which leaves us with some source diving to figure out all of them. Of course, since you know that the basic ones are documented, similar methods should just work the same.
Anyway, a pull request (or committing to lifo/docrails) improving the docs where necessary would be more than welcome :). Thanks!