Ruby-on-rails 限制每个 do 循环
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Limit each do loop
提问by Karl Entwistle
If I have the following,
如果我有以下内容，
<% @feed.sort_by{|t| - t.created_at.to_i}.each do |feed| %>
<% end %>
How can limit it to only show the 10 most recent results
如何将其限制为仅显示 10 个最近的结果
回答by J?rg W Mittag
<% @feed.sort_by{|t| - t.created_at.to_i}.first(10).each do |feed| %>
However, it's probably best to push this down into the model like this
但是，最好将其推入这样的模型中
<% @feed.recent(10).each do |feed| %>
And, in fact, if @feedcomes out of a database, I'd push it down even further: it doesn't make sense to load a ton of unsorted feed entries out of the DB, then sort them and then throw most of them away. Better let the DB do the sorting and filtering.
而且，事实上，如果@feed来自数据库，我会将其进一步推低：从数据库中加载大量未排序的提要条目，然后对它们进行排序，然后将其中大部分扔掉是没有意义的. 最好让 DB 进行排序和过滤。
See @Peer Allan's answer for how to do it in ActiveRecord. In ARel(IOW: Rails 3) it would probably be even simpler, something like
有关如何在ActiveRecord. 在ARel(IOW: Rails 3) 中，它可能会更简单，比如
Feed.all.order('created_at DESC').take(10)
回答by Bryan Ash
回答by alemur
I'd do it like this:
我会这样做：
<% @array.limit(10).each do |a| %>
回答by Amadan
I agree with the others (J?rg in particular); but if you still want to know how to limit the loop itself, breakcan be useful.
我同意其他人（特别是 J?rg）；但是如果您仍然想知道如何限制循环本身，break可能会很有用。
@array.each_with_index do |feed, i|
break if i == 10;
# ...
回答by Omer Aslam
The following code will return 10 recent records.
以下代码将返回 10 条最近的记录。
@feed = @feed.sort! { |a,b| b.created_at <=> a.created_at }.take(10)
回答by Peer Allan
The created_at seems to indicate that you are using ActiveRecord in Rails to get set the @feed variable. If that is the case you are better to do this work in SQL. Its far more efficient and easier to deal with.
created_at 似乎表明您在 Rails 中使用 ActiveRecord 来设置 @feed 变量。如果是这种情况，您最好在 SQL 中完成这项工作。它更有效，更容易处理。
@feed = Feed.all(:order => 'created_at DESC', :limit => 10)
Otherwise if you really want to use the view to do this you can use first or a range
否则，如果您真的想使用视图来执行此操作，则可以使用 first 或范围
<% @feed.sort_by{|t| - t.created_at.to_i}[0..9].each do |feed| %>
<% @feed.sort_by{|t| - t.created_at.to_i}.first(10).each do |feed| %>
