How to query a model based on attribute of another model which belongs to the first model?
active-record-query, activerecord, ruby-on-rails
Solution
You can do as following:
Person.includes(:vehicles).where(vehicles: { vehicle_type: 'auto' })
Person.includes(:vehicles).where(vehicles: { vehicle_type: 'motorcycle' })
Be careful with `.joins` and `.includes`:
# consider these models
Post # table name is posts
belongs_to :user
#^^
User # table name is users
has_many :posts
#^
# the `includes/joins` methods use the relation name defined in the model:
User.includes(:posts).where(posts: { title: 'Bobby Table' })
#^ ^
# but the `where` uses the exact table name:
Post.includes(:user).where(users: { name: 'Bobby' })
#^^^ ^
A tricky one:
Post
belongs_to :author, class_name: 'User'
User # table named users
has_many :posts
Post.includes(:author).where(users: { name: 'John' })
# because table is named users
Alternatively, the gem activerecord_where_assoc can achieve this (and much more):
Person.where_assoc_exists(:vehicles, vehicle_type: 'auto')
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Problem
If I have a model `Person`, which `has_many` `Vehicles` and each `Vehicle` can be of type `car` or `motorcycle`, how can I query for all persons, who have cars and all persons, who have motorcycles? I don't think these are correct: ``` Person.joins(:vehicles).where(vehicle_type: 'auto') Person.joins(:vehicles).where(vehicle_type: 'motorcycle') ```