Question

我创建了一个Spam类型的新对象，attr_accessor既有hooray又有名字，我有初始化方法。我期待当我创建一个新对象时，该对象加载了一个带有“Whammy”的var变量和一个名为hooray的空数组。虽然我没有得到这种行为。谁能解释一下，谢谢你。

module Test
class Spam
 attr_accessor :hooray, :name

 def initialize
    hooray = []
    name = "Whammy"
 end
end 
end

Loading development environment (Rails 3.0.0)
irb(main):001:0> require 'Test'
=> nil
irb(main):002:0> test = Test::Spam.new
=> #<Test::Spam:0x000000031ff470>
irb(main):003:0> test.name
=> nil
irb(main):004:0> test.hooray
=> nil
irb(main):005:0> test.hooray << 5
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.<<
    from (irb):5
    from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/commands/console.rb:44:in `start'
    from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/commands/console.rb:8:in `start'
    from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
irb(main):006:0>

Answer 1

这里的问题是你试图直接在initialize方法中使用setter，但Ruby将其解释为创建局部变量，而不是调用self上的setter。

 def initialize
    hooray = []
    name = "Whammy"
 end

您可以通过以下两种方式解决此问题;直接设置属性，例如@attribute：

 def initialize
    @hooray = []
    @name = "Whammy"
 end

或者，如果你真的想要通过setter（例如，如果你有自定义setter做一些有趣的事情），请用self.setter明确说明：

 def initialize
    self.hooray = []
    self.name = "Whammy"
 end

Answer 2

您希望在类的实例中使用实例变量来定义属性，而不是局部变量。方法执行完毕后，局部变量将超出范围。下面的代码应该更符合您的需求：

module Test
class Spam
 attr_accessor :hooray, :name

 def initialize
    @hooray = []
    @name = "Whammy"
 end
end 
end

初始化Ruby对象中的属性

2 个答案: