sinatra - 我在datamapper中尝试 “all”方法时发生错误

Question

当我尝试在Sinatra中执行此操作时，

class Comment
    include DataMapper::Resource
    property :id,           Serial
    property :body,         Text
    property :created_at, DateTime
end

get '/show' do
  comment = Comment.all
  @comment.each do |comment|
    "#{comment.body}"
  end
end

It returns this error,

ERROR: undefined method `bytesize' for #<Comment:0x13a2248>

谁能指出我正确的方向？

谢谢，

Answer 1

之所以收到此错误，是因为Sinatra会获取路由的返回值并将其转换为字符串，然后再尝试将其显示给客户端。

我建议您使用 View /模板来实现您的目标:

# file: <your sinatra file>
get '/show' do
  @comments = Comment.all
  erb :comments
end

# file: views/comments.erb
<% if !@comments.empty? %>
  <ul>
    <% @comments.each do |comment| %>
      <li><%= comment.body %></li>
    <% end %>
  </ul>
<% else %>
    Sorry, no comments to display.
<% end %>

或将您的注释附加到String变量，并在完成后返回它:

get '/show' do
  comments = Comment.all

  output = ""
  comments.each do |comment|
    output << "#{comment.body} <br />"
  end

  return output
end