attr_accessor初始化值
今天在写接口的时候想attr_accessor初始化值,查了好像没有现成的吧。
def Foo
@fields.each do |field_key,field_attr|
define_method("#{field_key}=") do |value|
instance_variable_set "@#{field_key}", self.class.type_value(field_attr,value)
end
define_method("#{field_key}") do
instance_variable_set "@#{field_key}", self.class.type_value(field_attr)
end
end
end
然后发现实例方法被nil重写,看了许久发现问题。
define_method("#{field_key}") do
instance_variable_get("@#{field_key}") ||
(instance_variable_set "@#{field_key}", self.class.type_value(field_attr) )
end
end
class Cat
# The below method could be defined in Module directly
def self.defaulted_attributes(attributes)
attributes.each do |attr, default|
attr_writer attr
define_method(attr) do
instance_variable_get("@#{attr}") ||
instance_variable_set("@#{attr}", default)
end
end
end
defaulted_attributes :amount_of_feet => 4
end
calin = Cat.new
print "calin had #{calin.amount_of_feet} feet... "
calin.amount_of_feet -= 1
puts "but I cut one of them, he now has #{calin.amount_of_feet}"
参考: How to initialize 'attr_accessor' attribute values? http://stackoverflow.com/questions/7081477/how-to-initialize-attr-accessor-attribute-values