Rails 2.3.8 named_scope链接

Question

我有以下嵌套的if语句hairball，我想知道是否有更有效的方式来编写此代码（不需要这么多条件的代码行）

每种方法都named_scopes模型中..

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，我可以用一个“呼叫”型方法的框，显示像

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

也许..？

哎，应该花一点更多的时间玩了..其正当我以为，我只是使用了错误的方法SOLUTION

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

Answer 1

您可以使用轨道2.3.8的scoped()方法链范围：

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

这是我想通了，我不会标记我自己的答案是正确的，除非大家同意这是最好的 - 10其他想法？

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 

Answer 3

你的答案是非常接近，但它无法转换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) 

这是假设你弄死了.all您正在使用的原代码所有选项，消失在你的答案。