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commit c86915450af4ee800ca3eba474fe6d01c865c4c3 1 parent cef442f
Rizwan Reza rizwanreza authored
3  activerecord/lib/active_record/errors.rb
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@@ -1,4 +1,7 @@
module ActiveRecord
+
+ # = Active Record Errors
+ #
# Generic Active Record exception class.
class ActiveRecordError < StandardError
end
98 activerecord/lib/active_record/migration.rb
View
@@ -29,11 +29,15 @@ def initialize(name)
end
end
- # Migrations can manage the evolution of a schema used by several physical databases. It's a solution
- # to the common problem of adding a field to make a new feature work in your local database, but being unsure of how to
- # push that change to other developers and to the production server. With migrations, you can describe the transformations
- # in self-contained classes that can be checked into version control systems and executed against another database that
- # might be one, two, or five versions behind.
+ # Active Record Migrations
+ #
+ # Migrations can manage the evolution of a schema used by several physical
+ # databases. It's a solution to the common problem of adding a field to make
+ # a new feature work in your local database, but being unsure of how to
+ # push that change to other developers and to the production server. With
+ # migrations, you can describe the transformations in self-contained classes
+ # that can be checked into version control systems and executed against
+ # another database that might be one, two, or five versions behind.
#
# Example of a simple migration:
#
@@ -47,10 +51,13 @@ def initialize(name)
# end
# end
#
- # This migration will add a boolean flag to the accounts table and remove it if you're backing out of the migration.
- # It shows how all migrations have two class methods +up+ and +down+ that describes the transformations required to implement
- # or remove the migration. These methods can consist of both the migration specific methods like add_column and remove_column,
- # but may also contain regular Ruby code for generating data needed for the transformations.
+ # This migration will add a boolean flag to the accounts table and remove it
+ # if you're backing out of the migration. It shows how all migrations have
+ # two class methods +up+ and +down+ that describes the transformations
+ # required to implement or remove the migration. These methods can consist
+ # of both the migration specific methods like add_column and remove_column,
+ # but may also contain regular Ruby code for generating data needed for the
+ # transformations.
#
# Example of a more complex migration that also needs to initialize data:
#
@@ -64,7 +71,9 @@ def initialize(name)
# t.integer :position
# end
#
- # SystemSetting.create :name => "notice", :label => "Use notice?", :value => 1
+ # SystemSetting.create :name => "notice",
+ # :label => "Use notice?",
+ # :value => 1
# end
#
# def self.down
@@ -72,35 +81,49 @@ def initialize(name)
# end
# end
#
- # This migration first adds the system_settings table, then creates the very first row in it using the Active Record model
- # that relies on the table. It also uses the more advanced create_table syntax where you can specify a complete table schema
- # in one block call.
+ # This migration first adds the system_settings table, then creates the very
+ # first row in it using the Active Record model that relies on the table. It
+ # also uses the more advanced create_table syntax where you can specify a
+ # complete table schema in one block call.
#
# == Available transformations
#
- # * <tt>create_table(name, options)</tt> Creates a table called +name+ and makes the table object available to a block
- # that can then add columns to it, following the same format as add_column. See example above. The options hash is for
- # fragments like "DEFAULT CHARSET=UTF-8" that are appended to the create table definition.
+ # * <tt>create_table(name, options)</tt> Creates a table called +name+ and
+ # makes the table object available to a block that can then add columns to it,
+ # following the same format as add_column. See example above. The options hash
+ # is for fragments like "DEFAULT CHARSET=UTF-8" that are appended to the create
+ # table definition.
# * <tt>drop_table(name)</tt>: Drops the table called +name+.
- # * <tt>rename_table(old_name, new_name)</tt>: Renames the table called +old_name+ to +new_name+.
- # * <tt>add_column(table_name, column_name, type, options)</tt>: Adds a new column to the table called +table_name+
+ # * <tt>rename_table(old_name, new_name)</tt>: Renames the table called +old_name+
+ # to +new_name+.
+ # * <tt>add_column(table_name, column_name, type, options)</tt>: Adds a new column
+ # to the table called +table_name+
# named +column_name+ specified to be one of the following types:
- # <tt>:string</tt>, <tt>:text</tt>, <tt>:integer</tt>, <tt>:float</tt>, <tt>:decimal</tt>, <tt>:datetime</tt>, <tt>:timestamp</tt>, <tt>:time</tt>,
- # <tt>:date</tt>, <tt>:binary</tt>, <tt>:boolean</tt>. A default value can be specified by passing an
- # +options+ hash like <tt>{ :default => 11 }</tt>. Other options include <tt>:limit</tt> and <tt>:null</tt> (e.g. <tt>{ :limit => 50, :null => false }</tt>)
- # -- see ActiveRecord::ConnectionAdapters::TableDefinition#column for details.
- # * <tt>rename_column(table_name, column_name, new_column_name)</tt>: Renames a column but keeps the type and content.
- # * <tt>change_column(table_name, column_name, type, options)</tt>: Changes the column to a different type using the same
- # parameters as add_column.
- # * <tt>remove_column(table_name, column_name)</tt>: Removes the column named +column_name+ from the table called +table_name+.
- # * <tt>add_index(table_name, column_names, options)</tt>: Adds a new index with the name of the column. Other options include
- # <tt>:name</tt> and <tt>:unique</tt> (e.g. <tt>{ :name => "users_name_index", :unique => true }</tt>).
- # * <tt>remove_index(table_name, index_name)</tt>: Removes the index specified by +index_name+.
+ # <tt>:string</tt>, <tt>:text</tt>, <tt>:integer</tt>, <tt>:float</tt>,
+ # <tt>:decimal</tt>, <tt>:datetime</tt>, <tt>:timestamp</tt>, <tt>:time</tt>,
+ # <tt>:date</tt>, <tt>:binary</tt>, <tt>:boolean</tt>. A default value can be
+ # specified by passing an +options+ hash like <tt>{ :default => 11 }</tt>.
+ # Other options include <tt>:limit</tt> and <tt>:null</tt> (e.g.
+ # <tt>{ :limit => 50, :null => false }</tt>) -- see
+ # ActiveRecord::ConnectionAdapters::TableDefinition#column for details.
+ # * <tt>rename_column(table_name, column_name, new_column_name)</tt>: Renames
+ # a column but keeps the type and content.
+ # * <tt>change_column(table_name, column_name, type, options)</tt>: Changes
+ # the column to a different type using the same parameters as add_column.
+ # * <tt>remove_column(table_name, column_name)</tt>: Removes the column named
+ # +column_name+ from the table called +table_name+.
+ # * <tt>add_index(table_name, column_names, options)</tt>: Adds a new index
+ # with the name of the column. Other options include
+ # <tt>:name</tt> and <tt>:unique</tt> (e.g.
+ # <tt>{ :name => "users_name_index", :unique => true }</tt>).
+ # * <tt>remove_index(table_name, index_name)</tt>: Removes the index specified
+ # by +index_name+.
#
# == Irreversible transformations
#
- # Some transformations are destructive in a manner that cannot be reversed. Migrations of that kind should raise
- # an <tt>ActiveRecord::IrreversibleMigration</tt> exception in their +down+ method.
+ # Some transformations are destructive in a manner that cannot be reversed.
+ # Migrations of that kind should raise an <tt>ActiveRecord::IrreversibleMigration</tt>
+ # exception in their +down+ method.
#
# == Running migrations from within Rails
#
@@ -110,13 +133,15 @@ def initialize(name)
# rails generate migration MyNewMigration
#
# where MyNewMigration is the name of your migration. The generator will
- # create an empty migration file <tt>timestamp_my_new_migration.rb</tt> in the <tt>db/migrate/</tt>
- # directory where <tt>timestamp</tt> is the UTC formatted date and time that the migration was generated.
+ # create an empty migration file <tt>timestamp_my_new_migration.rb</tt>
+ # in the <tt>db/migrate/</tt> directory where <tt>timestamp</tt> is the
+ # UTC formatted date and time that the migration was generated.
#
# You may then edit the <tt>self.up</tt> and <tt>self.down</tt> methods of
# MyNewMigration.
#
# There is a special syntactic shortcut to generate migrations that add fields to a table.
+ #
# rails generate migration add_fieldname_to_tablename fieldname:string
#
# This will generate the file <tt>timestamp_add_fieldname_to_tablename</tt>, which will look like this:
@@ -191,9 +216,10 @@ def initialize(name)
#
# == Using a model after changing its table
#
- # Sometimes you'll want to add a column in a migration and populate it immediately after. In that case, you'll need
- # to make a call to Base#reset_column_information in order to ensure that the model has the latest column data from
- # after the new column was added. Example:
+ # Sometimes you'll want to add a column in a migration and populate it
+ # immediately after. In that case, you'll need to make a call to
+ # <tt>Base#reset_column_information</tt> in order to ensure that the model has the
+ # latest column data from after the new column was added. Example:
#
# class AddPeopleSalary < ActiveRecord::Migration
# def self.up
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