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
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
require "active_support/core_ext/array"
require "active_support/core_ext/hash/except"
require "active_support/core_ext/kernel/singleton_class"
module ActiveRecord
# = Active Record \Named \Scopes
module Scoping
module Named
extend ActiveSupport::Concern
module ClassMethods
# Returns an ActiveRecord::Relation scope object.
#
# posts = Post.all
# posts.size # Fires "select count(*) from posts" and returns the count
# posts.each {|p| puts p.name } # Fires "select * from posts" and loads post objects
#
# fruits = Fruit.all
# fruits = fruits.where(color: 'red') if options[:red_only]
# fruits = fruits.limit(10) if limited?
#
# You can define a scope that applies to all finders using
# {default_scope}[rdoc-ref:Scoping::Default::ClassMethods#default_scope].
def all
if current_scope
current_scope.clone
else
default_scoped
end
end
def default_scoped # :nodoc:
scope = build_default_scope
if scope
relation.spawn.merge!(scope)
else
relation
end
end
# Adds a class method for retrieving and querying objects.
# The method is intended to return an ActiveRecord::Relation
# object, which is composable with other scopes.
# If it returns +nil+ or +false+, an
# {all}[rdoc-ref:Scoping::Named::ClassMethods#all] scope is returned instead.
#
# A \scope represents a narrowing of a database query, such as
# <tt>where(color: :red).select('shirts.*').includes(:washing_instructions)</tt>.
#
# class Shirt < ActiveRecord::Base
# scope :red, -> { where(color: 'red') }
# scope :dry_clean_only, -> { joins(:washing_instructions).where('washing_instructions.dry_clean_only = ?', true) }
# end
#
# The above calls to #scope define class methods <tt>Shirt.red</tt> and
# <tt>Shirt.dry_clean_only</tt>. <tt>Shirt.red</tt>, in effect,
# represents the query <tt>Shirt.where(color: 'red')</tt>.
#
# You should always pass a callable object to the scopes defined
# with #scope. This ensures that the scope is re-evaluated each
# time it is called.
#
# Note that this is simply 'syntactic sugar' for defining an actual
# class method:
#
# class Shirt < ActiveRecord::Base
# def self.red
# where(color: 'red')
# end
# end
#
# Unlike <tt>Shirt.find(...)</tt>, however, the object returned by
# <tt>Shirt.red</tt> is not an Array but an ActiveRecord::Relation,
# which is composable with other scopes; it resembles the association object
# constructed by a {has_many}[rdoc-ref:Associations::ClassMethods#has_many]
# declaration. For instance, you can invoke <tt>Shirt.red.first</tt>, <tt>Shirt.red.count</tt>,
# <tt>Shirt.red.where(size: 'small')</tt>. Also, just as with the
# association objects, named \scopes act like an Array, implementing
# Enumerable; <tt>Shirt.red.each(&block)</tt>, <tt>Shirt.red.first</tt>,
# and <tt>Shirt.red.inject(memo, &block)</tt> all behave as if
# <tt>Shirt.red</tt> really was an array.
#
# These named \scopes are composable. For instance,
# <tt>Shirt.red.dry_clean_only</tt> will produce all shirts that are
# both red and dry clean only. Nested finds and calculations also work
# with these compositions: <tt>Shirt.red.dry_clean_only.count</tt>
# returns the number of garments for which these criteria obtain.
# Similarly with <tt>Shirt.red.dry_clean_only.average(:thread_count)</tt>.
#
# All scopes are available as class methods on the ActiveRecord::Base
# descendant upon which the \scopes were defined. But they are also
# available to {has_many}[rdoc-ref:Associations::ClassMethods#has_many]
# associations. If,
#
# class Person < ActiveRecord::Base
# has_many :shirts
# end
#
# then <tt>elton.shirts.red.dry_clean_only</tt> will return all of
# Elton's red, dry clean only shirts.
#
# \Named scopes can also have extensions, just as with
# {has_many}[rdoc-ref:Associations::ClassMethods#has_many] declarations:
#
# class Shirt < ActiveRecord::Base
# scope :red, -> { where(color: 'red') } do
# def dom_id
# 'red_shirts'
# end
# end
# end
#
# Scopes can also be used while creating/building a record.
#
# class Article < ActiveRecord::Base
# scope :published, -> { where(published: true) }
# end
#
# Article.published.new.published # => true
# Article.published.create.published # => true
#
# \Class methods on your model are automatically available
# on scopes. Assuming the following setup:
#
# class Article < ActiveRecord::Base
# scope :published, -> { where(published: true) }
# scope :featured, -> { where(featured: true) }
#
# def self.latest_article
# order('published_at desc').first
# end
#
# def self.titles
# pluck(:title)
# end
# end
#
# We are able to call the methods like this:
#
# Article.published.featured.latest_article
# Article.featured.titles
def scope(name, body, &block)
unless body.respond_to?(:call)
raise ArgumentError, "The scope body needs to be callable."
end
if dangerous_class_method?(name)
raise ArgumentError, "You tried to define a scope named \"#{name}\" " \
"on the model \"#{self.name}\", but Active Record already defined " \
"a class method with the same name."
end
valid_scope_name?(name)
extension = Module.new(&block) if block
if body.respond_to?(:to_proc)
singleton_class.send(:define_method, name) do |*args|
scope = all.scoping { instance_exec(*args, &body) }
scope = scope.extending(extension) if extension
scope || all
end
else
singleton_class.send(:define_method, name) do |*args|
scope = all.scoping { body.call(*args) }
scope = scope.extending(extension) if extension
scope || all
end
end
end
protected
def valid_scope_name?(name)
if respond_to?(name, true) && logger
logger.warn "Creating scope :#{name}. " \
"Overwriting existing method #{self.name}.#{name}."
end
end
end
end
end
end
|
