Ruby on Rails中和之间的区别是什么？

Does it have something to do with output?

它与输出有关吗？

So, <%= ...code... %> is used for outputting after code is executed, and <% ...code... %> is only used for executing the code?

因此，<％= ... code ...％>用于在执行代码后输出，<％... code ...％>仅用于执行代码？

3 个解决方案

#1

This is ERB templating markup (one of many templating languages supported by Rails). This markup:

这是ERB模板标记（Rails支持的许多模板语言之一）。这个标记：

<% ... %>

is used to evaluate a Ruby expression. Nothing is done with the result of that expression, however. By contrast, the markup:

用于评估Ruby表达式。但是，该表达式的结果没有做任何事情。相比之下，加价：

<%= ... %>

does the same thing (runs whatever Ruby code is inside there) but it calls to_s on the result and replaces the markup with the resulting string.

做同样的事情（运行里面的任何Ruby代码）但它在结果上调用to_s并用结果字符串替换标记。

In short:

简而言之：

<% just run code %>
<%= run code and output the result %>

For example:

例如：

<% unless @items.empty? %>
  <ul>
    <% @items.each do |item| %>
      <li><%= item.name %></li>
    <% end %>
  </ul> 
<% end %>

In contrast, here's some Haml markup equivalent to the above:

相比之下，这里有一些等同于上面的Haml标记：

- unless @items.empty?
  %ul
    - @items.each do |item|
      %li= item.name

#2

Both execute the Ruby code contained within them. However, the different is in what they do with the returned value of the expression. <% ... %> will do nothing with the value. <%= ... %> will output the return value to whatever document it is executed in (typically a .erb or .rhtml document).

两者都执行其中包含的Ruby代码。但是，不同之处在于它们对表达式返回值的处理方式。 <％...％>对值无效。 <％= ...％>会将返回值输出到执行的任何文档（通常是.erb或.rhtml文档）。

Something to note, <%= ... %> will automatically escape any HTML contained in text. If you want to include any conditional HTML statements, do it outside the <% ... %>.

需要注意的是，<％= ...％>将自动转义文本中包含的任何HTML。如果要包含任何条件HTML语句，请在<％...％>之外执行。

<%= "<br />" if need_line_break %> <!-- Won't work -->

<% if need_line_break %>
<br />
<% end %> <!-- Will work -->

#3

<%= is used to output the value of a single expression, e.g.

<％=用于输出单个表达式的值，例如

<%= object.attribute %>
<%= link_to 'Link Title', link_path %>

while <% is used to execute arbitrary Ruby code.

而<％用于执行任意Ruby代码。

#1