I have a model Edge that belongs to the other model Node twice through different foreign keys:
def Edge < ActiveRecord::Base
belongs_to :first, class_name: 'Node'
belongs_to :second, class_name: 'Node'
end
And I want to perform this query using ActiveRecord:
SELECT * FROM edges INNER JOIN nodes as first ON first.id = edges.first_id WHERE first.value = 5
I found the way to join association using .joins() method:
Edge.joins(:first)
But this produces query using a table name, not an association name, so in .where() method I have to explicitly use table name which breaks association abstraction.
Edge.joins(:first).where(nodes: {value: 5})
I can also explicitly use SQL query in .joins() method to define model alias:
Edge.joins('INNER JOIN nodes as first ON nodes.id = edges.first_id')
But this breaks even more abstraction.
I think there should be the way to automatically define table alias on join. Or maybe a way to write such function by myself. Something like:
def Edge < ActiveRecord::Base
...
def self.joins_alias
# Generate something like
# joins("INNER JOIN #{relation.table} as #{relation.alias} ON #{relation.alias}.#{relation.primary_key} = #{table}.#{relation.foreign_key}")
end
end
But I couldn't find any information about accessing information about specific relation like it's name, foreign key, etc. So how can I do it?
Also it seems strange to me that such obvious feature is so complicated even through Rails is on its 4th major version already. Maybe I'm missing something?
