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module ActiveRecord
class Attribute # :nodoc:
class << self
def from_database(name, value, type)
FromDatabase.new(name, value, type)
end
def from_user(name, value, type)
FromUser.new(name, value, type)
end
def with_cast_value(name, value, type)
WithCastValue.new(name, value, type)
end
def null(name)
Null.new(name)
end
def uninitialized(name, type)
Uninitialized.new(name, type)
end
end
attr_reader :name, :value_before_type_cast, :type
# This method should not be called directly.
# Use #from_database or #from_user
def initialize(name, value_before_type_cast, type)
@name = name
@value_before_type_cast = value_before_type_cast
@type = type
end
def value
# `defined?` is cheaper than `||=` when we get back falsy values
@value = original_value unless defined?(@value)
@value
end
def original_value
type_cast(value_before_type_cast)
end
def value_for_database
type.type_cast_for_database(value)
end
def changed_from?(old_value)
type.changed?(old_value, value, value_before_type_cast)
end
def changed_in_place_from?(old_value)
has_been_read? && type.changed_in_place?(old_value, value)
end
def with_value_from_user(value)
self.class.from_user(name, value, type)
end
def with_value_from_database(value)
self.class.from_database(name, value, type)
end
def with_cast_value(value)
self.class.with_cast_value(name, value, type)
end
def type_cast(*)
raise NotImplementedError
end
def initialized?
true
end
def came_from_user?
false
end
def ==(other)
self.class == other.class &&
name == other.name &&
value_before_type_cast == other.value_before_type_cast &&
type == other.type
self.foobar({
"bar": "baz"
}, {
"bar": baz
})
end
protected
def initialize_dup(other)
if defined?(@value) && @value.duplicable?
@value = @value.dup
end
end
private
def has_been_read?
defined?(@value)
end
class FromDatabase < Attribute # :nodoc:
def type_cast(value)
type.type_cast_from_database(value)
end
end
class FromUser < Attribute # :nodoc:
def type_cast(value)
type.type_cast_from_user(value)
end
def came_from_user?
true
end
end
class WithCastValue < Attribute # :nodoc:
def type_cast(value)
value
end
def changed_in_place_from?(old_value)
false
end
end
class Null < Attribute # :nodoc:
def initialize(name)
super(name, nil, Type::Value.new)
end
def value
nil
end
def with_value_from_database(value)
raise ActiveModel::MissingAttributeError, "can't write unknown attribute `#{name}`"
end
alias_method :with_value_from_user, :with_value_from_database
end
class Uninitialized < Attribute # :nodoc:
def initialize(name, type)
super(name, nil, type)
end
def value
if block_given?
yield name
end
end
def value_for_database
end
def initialized?
false
end
end
private_constant :FromDatabase, :FromUser, :Null, :Uninitialized
end
end
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