class ActiveRecord::Migration::CommandRecorder
ActiveRecord::Migration::CommandRecorder
records commands done
during a migration and knows how to reverse those commands. The CommandRecorder knows how to invert the
following commands:
-
add_column
-
add_index
-
add_timestamps
-
create_table
-
create_join_table
-
remove_timestamps
-
rename_column
-
rename_index
-
rename_table
Attributes
commands[RW]
delegate[RW]
reverting[RW]
Public Class Methods
new(delegate = nil)
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# File lib/active_record/migration/command_recorder.rb, line 21 def initialize(delegate = nil) @commands = [] @delegate = delegate @reverting = false end
Public Instance Methods
change_table(table_name, options = {}) { |update_table_definition| ... }
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# File lib/active_record/migration/command_recorder.rb, line 88 def change_table(table_name, options = {}) yield delegate.update_table_definition(table_name, self) end
inverse_of(command, args, &block)
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Returns the inverse of the given command. For example:
recorder.inverse_of(:rename_table, [:old, :new]) # => [:rename_table, [:new, :old]]
This method will raise an IrreversibleMigration
exception if
it cannot invert the command
.
# File lib/active_record/migration/command_recorder.rb, line 63 def inverse_of(command, args, &block) method = :"invert_#{command}" raise IrreversibleMigration unless respond_to?(method, true) send(method, args, &block) end
record(*command, &block)
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record command
. command
should be a method name
and arguments. For example:
recorder.record(:method_name, [:arg1, :arg2])
# File lib/active_record/migration/command_recorder.rb, line 48 def record(*command, &block) if @reverting @commands << inverse_of(*command, &block) else @commands << (command << block) end end
revert() { || ... }
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While executing the given block, the recorded will be in reverting mode. All commands recorded will end up being recorded reverted and in reverse order. For example:
recorder.revert{ recorder.record(:rename_table, [:old, :new]) } # same effect as recorder.record(:rename_table, [:new, :old])
# File lib/active_record/migration/command_recorder.rb, line 34 def revert @reverting = !@reverting previous = @commands @commands = [] yield ensure @commands = previous.concat(@commands.reverse) @reverting = !@reverting end
Private Instance Methods
invert_add_index(args)
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# File lib/active_record/migration/command_recorder.rb, line 141 def invert_add_index(args) table, columns, options = *args options ||= {} index_name = options[:name] options_hash = index_name ? { name: index_name } : { column: columns } [:remove_index, [table, options_hash]] end
invert_change_column_null(args)
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# File lib/active_record/migration/command_recorder.rb, line 165 def invert_change_column_null(args) args[2] = !args[2] [:change_column_null, args] end
invert_drop_table(args, &block)
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Calls superclass method
# File lib/active_record/migration/command_recorder.rb, line 117 def invert_drop_table(args, &block) if args.size == 1 && block == nil raise ActiveRecord::IrreversibleMigration, "To avoid mistakes, drop_table is only reversible if given options or a block (can be empty)." end super end
invert_remove_column(args)
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Calls superclass method
# File lib/active_record/migration/command_recorder.rb, line 128 def invert_remove_column(args) raise ActiveRecord::IrreversibleMigration, "remove_column is only reversible if given a type." if args.size <= 2 super end
invert_remove_index(args)
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# File lib/active_record/migration/command_recorder.rb, line 151 def invert_remove_index(args) table, options = *args unless options && options.is_a?(Hash) && options[:column] raise ActiveRecord::IrreversibleMigration, "remove_index is only reversible if given a :column option." end options = options.dup [:add_index, [table, options.delete(:column), options]] end
invert_rename_column(args)
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# File lib/active_record/migration/command_recorder.rb, line 137 def invert_rename_column(args) [:rename_column, [args.first] + args.last(2).reverse] end
invert_rename_index(args)
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# File lib/active_record/migration/command_recorder.rb, line 133 def invert_rename_index(args) [:rename_index, [args.first] + args.last(2).reverse] end
invert_rename_table(args)
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# File lib/active_record/migration/command_recorder.rb, line 124 def invert_rename_table(args) [:rename_table, args.reverse] end
method_missing(method, *args, &block)
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Forwards any missing method call to the target.
Calls superclass method
# File lib/active_record/migration/command_recorder.rb, line 171 def method_missing(method, *args, &block) if @delegate.respond_to?(method) @delegate.send(method, *args, &block) else super end end