在Rails中的ERB中之间有什么区别?

Can some one please describe the usage of the following characters which is used in ERB file:

请描述一下在ERB文件中使用的下列字符的用法:

<%   %>
<%=  %>
<%  -%>
<%#  %>

what's the usage of each one ?

每一个的用法是什么?

5 个解决方案

#1

<% %>

Executes the ruby code within the brackets.

在括号内执行ruby代码。

<%= %>

Prints something into erb file.

在erb文件中打印一些东西。

<% -%>

Avoids line break after expression.

在表达式之后避免换行。

<%# %>

Comments out code within brackets; not sent to client (as opposed to HTML comments).

注释在括号内的代码;不发送给客户端(与HTML注释相反)。

Visit Ruby Doc for more infos about ERB.

访问Ruby Doc以获得更多关于ERB的信息。

#2

<% %> and <%- and -%> are for any Ruby code, but doesn't output the results (e.g. if statements). the two are the same.

<% %>和<%-和-%>是任何Ruby代码，但不输出结果(如if语句)。两者是一样的。

<%= %> is for outputting the results of Ruby code

<%= %>用于输出Ruby代码的结果。

<%# %> is an ERB comment

<%# %>是一个ERB评论。

Here's a good guide: http://api.rubyonrails.org/classes/ActionView/Base.html

这里有一个很好的指南:http://api.rubyonrails.org/classes/ActionView/Base.html。

#3

Rails does not use the stdlib's ERB by default, it uses erubis. Sources: this dev's comment, ActionView's gemspec, accepted merge request I did while writing this.

Rails在默认情况下不使用stdlib的ERB，它使用了erubis。来源:这个dev的评论，ActionView的gemspec，接受合并请求我在写这个的时候做了。

There are behavior differences between them, in particular on how the hyphen operators %- and -% work.

它们之间存在行为差异，尤其是连字符运算符%-和-%的工作方式。

Documentation is scarce, Where is Ruby's ERB format "officially" defined? so what follows are empirical conclusions.

文档很少，Ruby的ERB格式“正式”定义在哪里?下面是经验结论。

All tests suppose:

所有测试假设:

require 'erb'
require 'erubis'

When you can use -

当你可以使用的时候。

• ERB: you must pass - to trim_mode option of ERB.new to use it.
• ERB:你必须通过ERB的trim_mode选项。新使用它。
• erubis: enabled by default.
• erubis:默认启用。

Examples:

例子:

begin ERB.new("<%= 'a' -%>\nb").result; rescue SyntaxError ; else raise; end
ERB.new("<%= 'a' -%>\nb"  , nil, '-') .result == 'ab'  or raise
Erubis::Eruby.new("<%= 'a' -%>  \n b").result == 'a b' or raise

What -% does:

什么- - - - - - %:

• ERB: remove the next character if it is a newline.

  删除下一个字符，如果它是一条新行。

• erubis:

  erubis:

  • in <% %> (without =), - is useless because <% %> and <% -%> are the same. <% %> removes the current line if it only contains whitespaces, and does nothing otherwise.

    在<% %>(不=)中，-是无效的，因为<% %>和<% -%>是相同的。<% %>删除当前行，如果它只包含空白，则无其他操作。

  • in <%= -%> (with =):

    在<%= -%> (with =):

    • remove the entire line if it only contains whitespaces
    • 删除整个行，如果它只包含空白。
    • else, if there is a non-space before the tag, and only whitesapces after, remove the whitespces that come after
    • 否则，如果在标签之前有一个非空格，然后只有白色的，移除后面的空白。
    • else, there is a non-space after the tag: do nothing
    • 另外，标签后面还有一个非空间:什么都不做。

Examples:

例子:

# Remove
ERB.new("a \nb <% 0 -%>\n c", nil, '-').result == "a \nb  c" or raise

# Don't do anything: not followed by newline, but by space:
ERB.new("a\n<% 0 -%> \nc", nil, '-').result == "a\nb \nc" or raise

# Remove the current line because only whitesapaces:
Erubis::Eruby.new(" <% 0 %> \nb").result == 'b' or raise

# Same as above, thus useless because longer.
Erubis::Eruby.new(" <% 0 -%> \nb").result == 'b' or raise

# Don't do anything because line not empty.
Erubis::Eruby.new("a <% 0 %> \nb").result == "a  \nb" or raise
Erubis::Eruby.new(" <% 0 %> a\nb").result == "  a\nb" or raise
Erubis::Eruby.new(" <% 0 -%> a\nb").result == "  a\nb" or raise

# Don't remove the current line because of `=`:
Erubis::Eruby.new(" <%= 0 %> \nb").result == " 0 \nb" or raise

# Remove the current line even with `=`:
Erubis::Eruby.new(" <%= 0 -%> \nb").result == " 0b"   or raise

# Remove forward only because of `-` and non space before:
Erubis::Eruby.new("a <%= 0 -%> \nb").result == "a 0b"   or raise

# Don't do anything because non-whitespace forward:
Erubis::Eruby.new(" <%= 0 -%> a\nb").result == " 0 a\nb"   or raise

What %- does:

什么% -:

• ERB: remove whitespaces before tag and after previous newlines, but only if there are only whitespaces before.

  ERB:在标签之前和之前的换行之前删除空白，但前提是之前只有空白。

• erubis: useless because <%- %> is the same as <% %> (without =), and this cannot be used with = which is the only case where -% can be useful. So never use this.

  因为<%- %>与<% %>(没有=)是一样的，所以不能用= =这是唯一的情况-%是有用的。所以不要用这个。

Examples:

例子:

# Remove
ERB.new("a \n  <%- 0 %> b\n c", nil, '-').result == "a \n b\n c" or raise

# b is not whitespace: do nothing:
ERB.new("a \nb  <%- 0 %> c\n d", nil, '-').result == "a \nb   c\n d" or raise

What %- and -% do together

%和-%一起做!

The exact combination of both effects separately.

两种效果的确切结合。

#4

I've added the <%% literal tag delimiter as an answer to this because of its obscurity. This will tell erb not to interpret the <% part of the tag which is necessary for js apps like displaying chart.js tooltips etc.

由于它的晦涩，我添加了<%% literal标记分隔符作为这个答案。这将告诉erb不要解释标签的<%部分，这是js应用程序如显示图表所必需的。js工具提示等。

Everything about ERB can be found here: https://docs.puppet.com/puppet/latest/reference/lang_template_erb.html#tags

所有关于ERB的内容都可以在这里找到:https://docs.puppet/latest/reference/lang_template_erb.html #标签。

#5

These are use in ruby on rails :-

这些在ruby on rails中使用:-。

<% %> :-

< % % >:-

The <% %> tags are used to execute Ruby code that does not return anything, such as conditions, loops or blocks. Eg :-

<% %>标记用于执行不返回任何内容的Ruby代码，例如条件、循环或块。如:-

<h1>Names of all the people</h1>
<% @people.each do |person| %>
  Name: <%= person.name %><br>
<% end %>

<%= %> :-

< % = % >:-

use to display the content .

用于显示内容。

Name: <%= person.name %><br>

<% -%>:-

< %—% >:-

Rails extends ERB, so that you can suppress the newline simply by adding a trailing hyphen to tags in Rails templates

Rails扩展了ERB，这样您就可以简单地通过在Rails模板中添加一个拖尾连字符来抑制换行。

<%# %>:-

< % # % >:-

comment out the code

注释掉的代码

<%# WRONG %>
Hi, Mr. <% puts "Frodo" %>