ruby - 初始化 Ruby 对象中的属性

Question

我创建了一个 Spam 类型的新对象，具有指向 hooray 和 name 的 attr_accessor，并且我有初始化方法。我期望当我创建一个新对象时，该对象加载了一个名称为“Whammy”的变量和一个名为 hooray 的空数组。虽然我没有得到这种行为。任何人都可以解释一下，提前谢谢。

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

这里的问题是您试图在 initialize 方法中直接使用 setter，但 Ruby 将此解释为创建局部变量，而不是在 self 上调用 setter .

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

您可以通过以下两种方式之一解决此问题；直接设置属性，如@attribute:

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

或者，如果您真的想通过 setter (例如，如果您有自定义 setter 来做一些有趣的事情)，请使用 self.setter 使其显式:

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