Question

使用模块（命名空间）完成教程。我收到以下错误：

    blog.rb:25:in `insert_random_comment': undefined method `<<' for 
    #<Blog::Comment:0x007f1370368be0> (NoMethodError)
    from modules.rb:13:in `<main>'

在insert_random_comment中，我放置了类和方法。该类是Blog :: Comment，并且没有显示＆lt;＆lt;的方法。所以我希望实例变量@comment是一个对象列表，但它是一个单个对象。我是否正确地说，在实例化博客帖子对象时，我应该使用包含内容的列表初始化评论？单击博客评论？

module.rb

post = Blog::Post.new   author: "Stevie G",
                        title: "A title",
                        body: "A body",
                        comments: Blog::Comment.new(    user: "Jeffrey Way",
                                                        body: "A Comment")

post.insert_random_comment

blog.rb

module Blog

  class Post
        attr_reader :author, :title, :body, :comments

        def initialize options
                @author = options[:author]
                @title  = options[:title]
                @body   = options[:body]
                @comments = options[:comments] || []
        end

        #*splat (only 1 splat in method signature)
        #first param, *comments
        # insert_comments first, second, *thirds, options, &block
        def insert_comment first, second, *thirds, options, &block
                comments.each { |c| @comments << c }
        end

        def insert_random_comment
                p @comments.class
                p @comments.methods
                @comments << Comment.new(user: "jose Mota", body: "A body")
        end
  end

  class Comment
        attr_reader :user, :body

        def initialize options
                @user = options[:user]
                @body = options[:body]
        end
  end
end

Answer 1

基于您的module.rb，在初始化Post对象时，您将Post.comments指定为Comment对象。

post = Blog::Post.new   author: "Stevie G",
                        title: "A title",
                        body: "A body",
                        comments: Blog::Comment.new(    user: "Jeffrey Way",
                                                        body: "A Comment")   #This is an object of Comment

所以你可以：

post = Blog::Post.new   author: "Stevie G",
                        title: "A title",
                        body: "A body",
                        comments: [Blog::Comment.new(    user: "Jeffrey Way",
                                                        body: "A Comment")]   #This is an Array of Comments

Answer 2

当你处理数组时，但是期望单个值可能作为输入出现，你可能想要使用ruby magick：

value = *[arg]

无论arg是否为数组，

都将保存一个数组：

arg = [1,2,3]
value = *[arg]
# => [
#   [0] [
#     [0] 1,
#     [1] 2,
#     [2] 3
#   ]
# ]

arg = 1
value = *[arg]
# => [
#   [0] [
#     [0] 1
#   ]
# ]

因此，在您的情况下，您可能希望使用单个注释或数组初始化对象：

@comments = [*options[:comments]]

会做的伎俩。问题是你在调用Comment（第四个参数）时传递了单个Blog::Post.new对象。

UPD：感谢@PatriceGahide，错误地处理了nil。

Ruby Undefined方法'＆lt;＆lt;'上课？

2 个答案: