includes(*args)
Instance Public methods
Specify relationships to be included in the result set. For example:
1 2 3 4 | users = User.includes(:address)users.each do |user| user.address.cityend |
allows you to access the address attribute of the
User model without firing an additional query. This will often
result in a performance improvement over a simple join.
You can also specify multiple relationships, like this:
1 | users = User.includes(:address, :friends) |
Loading nested relationships is possible using a Hash:
1 | users = User.includes(:address, friends: [:address, :followers]) |
conditions
If you want to add conditions to your included models you'll have to explicitly reference them. For example:
1 | User.includes(:posts).where('posts.name = ?', 'example') |
Will throw an error, but this will work:
1 | User.includes(:posts).where('posts.name = ?', 'example').references(:posts) |
Note that includes works with association names while
references needs the actual table name.
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