How to generate scaffold for data type with “extra description” in Rails 3?

问题

From Ruby on Rails: best method of handling currency / money, how do you generate a scaffold for the folowing:

add_column :items, :price, :decimal, :precision => 8, :scale => 2

Such as:

rails generate scaffold LineItem name:string \
                                 price:decimal {:precision => 8, :scale => 2}

Also, what is the correct term for "extra description" for the decimal type?

Working in Rails 3.07, Ruby 1.92

回答1:

In Rails 3.1 and below, the syntax is

rails generate scaffold LineItem name:string price:decimal

and then manually add the decimal properties to the migration file

t.decimal :price, :precision => 8, :scale => 2

In Rails 3.2, one can specify the decimal properties

rails generate scaffold LineItem name price:decimal{8,2}

NOTE: If you are running ZSH, the syntax requires a hyphen instead of a comma.

rails generate scaffold LineItem name price:decimal{8-2}

ANOTHER NOTE: If you are using bash under Mac OS X 10.9 try a dot instead of the comma

rails generate scaffold LineItem name price:decimal{8.2}

回答2:

A few years later, with Rails 4.2 and bash (Linux) the following generator command works without problems:

bin/rails generate scaffold LineItem name:string price:decimal{8.2}

This will correctly generate the following example migration:

class CreateLineItems < ActiveRecord::Migration
  def change
    create_table :line_items do |t|
      t.string :name
      t.decimal :price, precision: 8, scale: 2

      t.timestamps null: false
    end
  end
end

回答3:

Almost a year later. Rails 3.2.11. Regular bash shell. Rails scaffold creates mess with syntax field_name:decimal{p,s} regardless of railties official doc. The confusion lays in simple fact that curly braces are meta-characters in bash (as well as in other shells) and needs to be escaped. See logged issue 4602 in scaffold generator repo.

If you using bash then use dot instead of comma as workaround.
Correct scaffold syntax field_name:decimal{p.s}

回答4:

New approach:

Create the migration with just add_column, e.g. rails generate migration AddPriceToLineItem price:integer

Then edit the migration and change it to be how you want it, e.g.

add_column :line_items, :price, :decimal, :precision => 8, :scale => 2

Getting the command line exactly right to do this has proved to be a major exercise in frustration and wasted time for me in the past. I recommend you follow this procedure and move on.

回答5:

Here's how I did it:

rails generate scaffold LineItem ... amount:decimal ...

The ... are any other fields we need in the scaffold, like date:date, item:string, category:references...

Then I modified the migration to look like:

create_table :line_items do |t|
  .
  .
  .
  t.decimal :amount, :precision => 8, :scale => 2

Then

rake db:migrate

This holds values between -999,999.99 to 999,999.99.

Here is some (marginally) useful reference: http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html

回答6:

This is the accurate and most simple way to do this under Rails 5.x:

rails generate scaffold LineItem name price:decimal{'8,2'}

Pay special attention to the single quotes used when specifying scale and precision.

来源：https://stackoverflow.com/questions/9560233/how-to-generate-scaffold-for-data-type-with-extra-description-in-rails-3