Rails 2.3.8 named_scope 链接

Question

我有以下嵌套的 if 语句毛球，我想知道是否有更有效的方法来编写此代码（代码行更少，不需要这么多条件）

每个方法在模型中都被命名为_scopes..

box = (params[:b] ? params[:b] : "inbox")
show = (params[:s] ? params[:s] : "all")

if box == "inbox"
  if show == "all"
    @messages = @current_user.received_messages.all  
  elsif show == "unread"
    @messages = @current_user.received_messages.unread.all  
  elsif show == "read"
    @messages = @current_user.received_messages.read.all  
  elsif show == "starred"
    @messages = @current_user.received_messages.starred.all  
  else
    @messages = []
  end
elsif box = "sent"
  @messages = @current_user.sent_messages.all  
else
  @messages = []
end

我的想法是我可以对框使用“调用”类型的方法并显示类似

@current_user.received_messages.call(:box).call(:show).all

也许..？

呃，应该多花点时间玩一下..和我想的一样，我只是使用了错误的方法解决方案

@current_user.send(box).send(show)

Answer 1

您可以使用 rails 2.3.8 中的 scoped() 方法链接作用域：

main_method = case (params[:s]||"inbox")
when "inbox"
  :received_messages
when "sent"
  :sent_messages
end
# create a scope. Don't execute the scope yet. 
scope = @current_user.send(main_method).scoped({}) if main_method

# now chain the scope if needed
scope = begin
  if ["unread", "read", "starred"].include?(params[:s])
    scope.send(params[:s])
  elsif((params[:s] || "all") == "all")
    scope
  end
end if main_method == :received_messages

@messages = scope.nil? ? [] : scope.all

参考：

Scoped method source in Rails 2.3.x

Rails casts on Anonymous scopes in 2.3.x

Answer 2

您的答案非常接近，但无法转换 box 值。

box  = params[:b] || 'inbox'
show = params[:s] || 'all'

box_scope = case box
  when 'inbox' then 'received_messages'
  when 'sent'  then 'sent_messages'
end
show_scope = show # no convertion needed at this point, maybe in the future

# If box_scope is nil, don't query
@messages = box_scope.nil? ? [] : @current_user.send(box_scope).send(show_scope)

这假设您取消了您在 all 选项的原始代码中使用的.all，该选项在您的答案中消失了。

Answer 3

这是我想出来的，除非每个人都同意这是最好的，否则我不会将自己的答案标记为正确 - 还有其他想法吗？

if params[:b].present? && ["received_messages", "sent_messages"].include?(params[:b])
  box = params[:b]

  if params[:s].present? && ["all", "unread", "starred"].include?(params[:s])
    show = params[:s]
  else
    show = "all"
  end

  @messages = @current_user.send(box).send(show)
else
  @messages = []
end