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module ActiveRecord
module DynamicMatchers
def respond_to?(name, include_private = false)
match = Method.match(self, name)
match && match.valid? || super
end
private
# Enables dynamic finders like <tt>User.find_by_user_name(user_name)</tt> and
# <tt>User.scoped_by_user_name(user_name). Refer to Dynamic attribute-based finders
# section at the top of this file for more detailed information.
#
# It's even possible to use all the additional parameters to +find+. For example, the
# full interface for +find_all_by_amount+ is actually <tt>find_all_by_amount(amount, options)</tt>.
#
# Each dynamic finder using <tt>scoped_by_*</tt> is also defined in the class after it
# is first invoked, so that future attempts to use it do not run through method_missing.
def method_missing(name, *arguments, &block)
match = Method.match(self, name)
if match && match.valid?
match.define
send(name, *arguments, &block)
else
super
end
end
class Method
def self.match(model, name)
klass = klasses.find { |k| name =~ k.pattern }
klass.new(model, name) if klass
end
def self.klasses
[
FindBy, FindAllBy, FindLastBy, FindByBang, ScopedBy,
FindOrInitializeBy, FindOrCreateBy, FindOrCreateByBang
]
end
def self.pattern
/^#{prefix}_([_a-zA-Z]\w*)#{suffix}$/
end
def self.prefix
raise NotImplementedError
end
def self.suffix
''
end
attr_reader :model, :name, :attribute_names
def initialize(model, name)
@model = model
@name = name.to_s
@attribute_names = @name.match(self.class.pattern)[1].split('_and_')
end
def valid?
attribute_names.all? { |name| model.columns_hash[name] || model.reflect_on_aggregation(name.to_sym) }
end
def define
model.class_eval <<-CODE, __FILE__, __LINE__ + 1
def self.#{name}(#{signature})
#{body}
end
CODE
end
def body
raise NotImplementedError
end
end
class Finder < Method
def body
<<-CODE
result = #{result}
result && block_given? ? yield(result) : result
CODE
end
def result
"scoped.apply_finder_options(options).#{finder}(#{attributes_hash})"
end
def signature
attribute_names.join(', ') + ", options = {}"
end
def attributes_hash
"{" + attribute_names.map { |name| ":#{name} => #{name}" }.join(',') + "}"
end
def finder
raise NotImplementedError
end
end
class FindBy < Finder
def self.prefix
"find_by"
end
def finder
"find_by"
end
end
class FindByBang < Finder
def self.prefix
"find_by"
end
def self.suffix
"!"
end
def finder
"find_by!"
end
end
class FindAllBy < Finder
def self.prefix
"find_all_by"
end
def finder
"where"
end
def result
"#{super}.to_a"
end
end
class FindLastBy < Finder
def self.prefix
"find_last_by"
end
def finder
"where"
end
def result
"#{super}.last"
end
end
class ScopedBy < Finder
def self.prefix
"scoped_by"
end
def body
"where(#{attributes_hash})"
end
end
class Instantiator < Method
# This is nasty, but it doesn't matter because it will be deprecated.
def self.dispatch(klass, attribute_names, instantiator, args, block)
if args.length == 1 && args.first.is_a?(Hash)
attributes = args.first.stringify_keys
conditions = attributes.slice(*attribute_names)
rest = [attributes.except(*attribute_names)]
else
raise ArgumentError, "too few arguments" unless args.length >= attribute_names.length
conditions = Hash[attribute_names.map.with_index { |n, i| [n, args[i]] }]
rest = args.drop(attribute_names.length)
end
klass.where(conditions).first ||
klass.create_with(conditions).send(instantiator, *rest, &block)
end
def signature
"*args, &block"
end
def body
"#{self.class}.dispatch(self, #{attribute_names.inspect}, #{instantiator.inspect}, args, block)"
end
def instantiator
raise NotImplementedError
end
end
class FindOrInitializeBy < Instantiator
def self.prefix
"find_or_initialize_by"
end
def instantiator
"new"
end
end
class FindOrCreateBy < Instantiator
def self.prefix
"find_or_create_by"
end
def instantiator
"create"
end
end
class FindOrCreateByBang < Instantiator
def self.prefix
"find_or_create_by"
end
def self.suffix
"!"
end
def instantiator
"create!"
end
end
end
end
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