Rails:渲染集合部分:获取部分内部集合的大小 [英] Rails: Render collection partial: Getting size of collection inside partial

问题描述

我有一组我想用部分渲染的项目:

I have a collection of items I want to render with a partial:

@items = ['a','b','c']

<%= render :collection => @items, :partial => 'item' %>

我想用升序数字给元素编号.所以输出应该是:

and I want to number the elements with ascending numbers. So the output should be:

3: a
2: b
1: c

我知道 rails 在部分内部提供了一个计数器，所以如果我想对项目降序进行编号，我可以创建以下部分:

I know rails provides a counter inside the partial, so if I wanted to number the items descending, I could create the following partial:

<%= item_counter %>: <%= item %>

这给了我

1: a
2: b
3: c

但是对于升序数字，我需要项目的总数，我可以提供局部到局部:

But for the ascending numbers, I need the total number of items, which I could provide with a local to the partial:

<%= render :collection => @items, :partial => 'item', :locals => {:total => @items.size} %>

然后在部分:

<%= total - item_counter %>: <%= item %>

但对我来说感觉就像重复，因为render方法已经知道集合的大小.

But it feels to me like repetition, because the render method already knows about the size of the collection.

除了使用局部变量之外，真的没有办法获得部分内集合的项目总数吗?

推荐答案

以下是可能的自 Rails 4.2 版:

在部分内部，您可以访问名为 collection_iteration 的函数/变量.调用 collection_iteration.size 会给你总数.

Inside the partial you have access to a function/variable called collection_iteration. Calling collection_iteration.size will give you the total.

来自变更日志:

迭代对象可用作局部变量#{template_name}_iteration 使用集合渲染部分时.

The iteration object is available as the local variable #{template_name}_iteration when rendering partials with collections.

它可以访问正在迭代的集合的size，当前 index 和两个方便的方法 first? 和 last?.

It gives access to the size of the collection being iterated over, the current index and two convenience methods first? and last?.

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