我想初始化attr3='c'
,属性数量可以更改。
class MyClass
attr_accessor :attr1, :attr2, :attr3
def initialize(attr1 = 1, attr2 = 2, attr3 = 3)
@attr1 = attr1
@attr2 = attr2
@attr3 = attr3
end
end
myclass = MyClass.new
myclass.attr1 # => 1
myclass.attr2 # => 2
myclass.attr3 # => 3
myclass = MyClass.new('c')
myclass.attr1 # => c
myclass.attr2 # => 2
myclass.attr3 # => 3
我尝试为属性名称赋值。
myclass = MyClass.new({attr3 : 'c'}) # => but that doesn't work
答案 0 :(得分:1)
要使用命名默认值(假设您使用Ruby 2.0 and up):
def initialize(attr1: 1, attr2: 2, attr3: 3)
@attr1 = attr1
@attr2 = attr2
@attr3 = attr3
end
请注意,此方法不与之前的方法一起使用:
myclass = MyClass.new
myclass.attr1 # => 1
myclass.attr2 # => 2
myclass.attr3 # => 3
myclass = MyClass.new(attr1: 'c')
myclass.attr1 # => c
myclass.attr2 # => 2
myclass.attr3 # => 3
myclass = MyClass.new('c') # ERROR!
答案 1 :(得分:-1)
编写初始化程序以获取哈希:
def initialize(attributes = {})
# If the attributes hash doesn't have the relevant key, set it to default:
@attr1 = attributes.fetch(:attr1, 1)
@attr2 = attributes.fetch(:attr2, 2)
@attr3 = attributes.fetch(:attr3, 3)
end
对于更通用的解决方案,您可以遍历哈希中的键:
def initialize(attributes = {})
attributes.each do |key, value|
send("#{key}=", value) if respond_to?("#{key}=")
end
end