1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
|
module ActiveRecord
class Migration
# <tt>ActiveRecord::Migration::CommandRecorder</tt> 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
class CommandRecorder
include JoinTable
attr_accessor :commands, :delegate, :reverting
def initialize(delegate = nil)
@commands = []
@delegate = delegate
@reverting = false
end
# 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])
def revert
@reverting = !@reverting
previous = @commands
@commands = []
yield
ensure
@commands = previous.concat(@commands.reverse)
@reverting = !@reverting
end
# record +command+. +command+ should be a method name and arguments.
# For example:
#
# recorder.record(:method_name, [:arg1, :arg2])
def record(*command, &block)
if @reverting
@commands << inverse_of(*command, &block)
else
@commands << (command << block)
end
end
# 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+.
def inverse_of(command, args, &block)
method = :"invert_#{command}"
raise IrreversibleMigration unless respond_to?(method, true)
send(method, args, &block)
end
def respond_to?(*args) # :nodoc:
super || delegate.respond_to?(*args)
end
[:create_table, :create_join_table, :change_table, :rename_table, :add_column, :remove_column,
:rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps,
:change_column, :change_column_default, :add_reference, :remove_reference, :transaction,
].each do |method|
class_eval <<-EOV, __FILE__, __LINE__ + 1
def #{method}(*args, &block) # def create_table(*args, &block)
record(:"#{method}", args, &block) # record(:create_table, args, &block)
end # end
EOV
end
alias :add_belongs_to :add_reference
alias :remove_belongs_to :remove_reference
private
def invert_transaction(args, &block)
[:transaction, args, block]
end
def invert_create_table(args)
[:drop_table, [args.first]]
end
def invert_create_join_table(args)
table_name = find_join_table_name(*args)
[:drop_table, [table_name]]
end
def invert_rename_table(args)
[:rename_table, args.reverse]
end
def invert_add_column(args)
[:remove_column, args.first(2)]
end
def invert_rename_index(args)
[:rename_index, [args.first] + args.last(2).reverse]
end
def invert_rename_column(args)
[:rename_column, [args.first] + args.last(2).reverse]
end
def invert_add_index(args)
table, columns, options = *args
index_name = options.try(:[], :name)
options_hash = index_name ? {:name => index_name} : {:column => columns}
[:remove_index, [table, options_hash]]
end
def invert_remove_timestamps(args)
[:add_timestamps, args]
end
def invert_add_timestamps(args)
[:remove_timestamps, args]
end
def invert_add_reference(args)
[:remove_reference, args]
end
alias :invert_add_belongs_to :invert_add_reference
def invert_remove_reference(args)
[:add_reference, args]
end
alias :invert_remove_belongs_to :invert_remove_reference
# Forwards any missing method call to the \target.
def method_missing(method, *args, &block)
@delegate.send(method, *args, &block)
rescue NoMethodError => e
raise e, e.message.sub(/ for #<.*$/, " via proxy for #{@delegate}")
end
end
end
end
|
