Some stuff about Active Record
July 13, 2020 ( last updated : July 13, 2020 )
ruby
active-record
1. Active Record uses a column called type for object inheritance
Taken from the docs:
Active Record allows inheritance by storing the name of the class in a column that by default is named “type” (can be changed by overwriting Base.inheritance_column)
For example, when you have classes that look like this:
class Person < ActiveRecord::Base; end
class Child < Person; end
and create a child object
Child.create(name: 'Billy')
Active Record stores the value "Child" in billy’s type column. Then we can retrieve Billy
Person.where(name: 'Billy')
Active Record will use the value in type to return an object of type Child.
2. The method remove_column needs a type to be used in a change block.
The method signature for Active Record’s remove_column method looks like this:
remove_column(table_name, column_name, type = nil, options = {})
type and options are optional params that will be added to the add_column call if the migration is reversed. Neat.