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Principle of Least Surprise (Astonishment), foreign keys, and Rails
In yesterday’s post, I sorted through the foreigner gem to figure out how to change the reference column (primary key) that a foreign_key maps to. The problem here is that, unless your Rails project(s) has grown up referencing “natural” primary keys instead of the autoincremented id implicit in an ActiveRecord::Migration, avoiding creating surprise by not…
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foreigner foreign_key on a different column in source and target table.
In the foreigner gem, you can specify the foreign_key column on the source table by using the column option. class Cats < ActiveRecord::Migration def change create_table :cats do |t| t.integer :color_id t.integer :second_color_id t.timestamps end add_foreign_key :cats, :colors, column: :second_color_id end end But what about the target table? This can be accomplished using the primary_key…
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includes and has_many :through associations
I’ve been trying to mentally absorb how includes and associations work when trying to query a has_many :through association. My understanding at this point: The symbol in the includes() is the same as the association name on whatever model you have. For example: class Account < ActiveRecord::Base has_many :account_destinations has_many :destinations, through: :account_destinations end class…