2.3 Passing Modifiers
Some commonly used type modifiers can be passed directly on the command line. They are enclosed by curly braces and follow the field type:
For instance, running:
$ bin/rails generate migration AddDetailsToProducts 'price:decimal{5,2}' supplier:references{polymorphic}
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will produce a migration that looks like this
class AddDetailsToProducts < ActiveRecord::Migration
def change
add_column :products , :price , :decimal , precision: 5 , scale: 2
add_reference :products , :supplier , polymorphic: true , index: true
end
end
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Have a look at the generators help output for further details.
Advanced usage
Sometimes you have to automatically add index for columns in your migration. It’s not a problem:
$ rails g model user email:index location_id:integer:index
Or uniq index:
$ rails g model user pseudo:string:uniq
Set limit for field of integer, string, text and binary fields:
$ rails generate model user pseudo:string{30}
Special syntax to generate decimal field with scale and precision:
$ rails generate model product 'price:decimal{10,2}'
Pay attention that you have to wrap parameter price:decimal{10,2}
to quotes. It’s vital and you may have incorrect behavior of generator if you don’t do it. Full explanation of this case is here.
You can combine any single curly brace option with the index options:
$ rails generate model user username:string{30}:uniq
And the last useful feature of generators – it’s options to generate reference columns (fields which are used in rails as foreign keys):
$ rails generate model photo album:references
This command will generate photos table with integer field album_id and also it will add index for this field automatically. Make sure in it by looking at generated migration:
class CreatePhotos < ActiveRecord::Migration
def change
create_table :photos do |t|
t.references :album
t.timestamps
end
add_index :photos, :album_id
end
end
For polymorphic reference use this syntax:
$ rails generate model product supplier:references{polymorphic}
Polymorphic reference with indexes:
$ rails generate model product supplier:references{polymorphic}:index
Sources
http://railsguides.net/advanced-rails-model-generators/