Liquid语法

作者:lijiaocn  更新时间:2019-01-09 17:35:25 +0800

  编程    jekyll    刷新

目录

介绍

Liquidshopify公司开发的模版语言,shopify是一家电商软件开发公司。

liquid doc中介绍了liquid的语法。

Liquid code can be categorized into `objects`, `tags`, and `filters`。

Objects

Objects是用{{和}}围起来的liquid代码

Objects tell Liquid where to show content on a page. 
Objects and variable names are denoted by double curly braces: {{ and }}.

example:

{{ page.title }}

Tags

Tags是用{ %% }包裹起来的liquid代码,做逻辑处理和control flow。

Tags create the logic and control flow for templates. 
They are denoted by curly braces and percent signs: {% and %}.

分为Control flow、Iteration、Variable assignments三类。

Control flow

Control flow有三个:if-else,unless,case/when

if/elsif/else

{% if customer.name == 'kevin' %}
  Hey Kevin!
{% elsif customer.name == 'anonymous' %}
  Hey Anonymous!
{% else %}
  Hi Stranger!
{% endif %}

unless

{% unless product.title == 'Awesome Shoes' %}
  These shoes are not awesome.
{% endunless %}

case/when

{% assign handle = 'cake' %}
{% case handle %}
  {% when 'cake' %}
     This is a cake
  {% when 'cookie' %}
     This is a cookie
  {% else %}
     This is not a cake nor a cookie
{% endcase %}

Iteration

Iteration: for、

for/break/continue

{% for i in (1..5) %}
  {% if i == 4 %}
    {% continue %}
  {% else %}
    {{ i }}
  {% endif %}
{% endfor %}

{% for i in (1..5) %}
  {% if i == 4 %}
    {% break %}
  {% else %}
    {{ i }}
  {% endif %}
{% endfor %}

for(带参数)

limit,限制循环次数

<!-- if array = [1,2,3,4,5,6] -->
{% for item in array limit:2 %}
  {{ item }}
{% endfor %}

Output:

1 2

offset,设置开始位置

<!-- if array = [1,2,3,4,5,6] -->
{% for item in array offset:2 %}
  {{ item }}
{% endfor %}

Output:

3 4 5 6

(), 指定范围

{% for i in (3..5) %}
  {{ i }}
{% endfor %}

也可以是使用变量:

{% assign num = 4 %}
{% for i in (1..num) %}
  {{ i }}
{% endfor %}

reversed, 逆序

<!-- if array = [1,2,3,4,5,6] -->
{% for item in array reversed %}
  {{ item }}
{% endfor %}

Output

6 5 4 3 2 1

cycle in for

类似于生成器,每次吐出下一个字符串,但是必须在for中使用

Loops through a group of strings and outputs them in the order that they were passed as parameters. 
Each time cycle is called, the next string that was passed as a parameter is output.

example:

{% cycle 'one', 'two', 'three' %}
{% cycle 'one', 'two', 'three' %}
{% cycle 'one', 'two', 'three' %}
{% cycle 'one', 'two', 'three' %}

Output

one
two
three
one

tablerow

生成一个table,必须在table标签中使用

<table>
{% tablerow product in collection.products %}
  {{ product.title }}
{% endtablerow %}
</table>

Output:

<table>
  <tr class="row1">
    <td class="col1">
      Cool Shirt
    </td>
    <td class="col2">
      Alien Poster
    </td>
    <td class="col3">
      Batman Poster
    </td>
  </tr>
</table>

tablerow, 参数

cols,指定列数

{% tablerow product in collection.products cols:2 %}
  {{ product.title }}
{% endtablerow %}

Output

<table>
  <tr class="row1">
    <td class="col1">
      Cool Shirt
    </td>
    <td class="col2">
      Alien Poster
    </td>
  </tr>
  <tr class="row2">
    <td class="col1">
      Batman Poster
    </td>
    <td class="col2">
      Bullseye Shirt
    </td>
  </tr>
  <tr class="row3">
    <td class="col1">
      Another Classic Vinyl
    </td>
    <td class="col2">
      Awesome Jeans
    </td>
  </tr>
</table>

limit,限制表格项数目

{% tablerow product in collection.products cols:2 limit:3 %}
  {{ product.title }}
{% endtablerow %}

offset,指定开始位置

{% tablerow product in collection.products cols:2 offset:3 %}
  {{ product.title }}
{% endtablerow %}

(),range

<!--variable number example-->
{% assign num = 4 %}
<table>
{% tablerow i in (1..num) %}
  {{ i }}
{% endtablerow %}
</table>

<!--literal number example-->
<table>
{% tablerow i in (3..5) %}
  {{ i }}
{% endtablerow %}
</table>

Variable assignments

assign,创建变量

{% assign my_variable = false %}
{% if my_variable != true %}
  This statement is valid.
{% endif %}

{% assign foo = "bar" %}
{{ foo }}

capture, 捕获变量值,合并入新变量

{% capture my_variable %}I am being captured.{% endcapture %}
{{ my_variable }}

变量my_variable的值就是capture中字符串,如果其中有变量,变量解析成值。

increment,创建递增变量

初始值为0

{% increment my_counter %}
{% increment my_counter %}
{% increment my_counter %}

Output

0
1
2

注意increment中的变量和assign、capture创建的变量是相互独立的,仔细看下面列子的output:

{% assign var = 10 %}
{% increment var %}
{% increment var %}
{% increment var %}
{{ var }}

Output

0
1
2
10

decrement,创建递减变量

初始值为-1

{% decrement variable %}
{% decrement variable %}
{% decrement variable %}

Output

-1
-2
-3

和increment类似,decrement创建的变量是独立于assign、capture创建的变量的。

Filters

Filters用于改变输出的值

example

{{ "/my/fancy/url" | append: ".html" }}

Output

/my/fancy/url.html

可以连续使用

{{ "adam!" | capitalize | prepend: "Hello " }}

Output

Hello Adam!

filters列表

这是liquid提供的filter:

abs
append
capitalize
ceil
compact
date
default
divided_by
downcase
escape
escape_once
first
floor
join
last
lstrip
map
minus
modulo
newline_to_br
plus
prepend
remove
remove_first
replace
replace_first
reverse
round
rstrip
size
slice
sort
sort_natural
split
strip
strip_html
strip_newlines
times
truncate
truncatewords
uniq
upcase

运算符(Operators)

Basic

==     equals
!=     does not equal
>      greater than
<      less than
>=     greater than or equal to
<=     less than or equal to
or     logical or
and    logical and

contains, 字符串包含判断

可以判断字符串中是否包含字符串:

{% if product.title contains 'Pack' %}
  This product's title contains the word Pack.
{% endif %}

也可以判断字符串数组中是否包含字符串:

{% if product.tags contains 'Hello' %}
  This product has been tagged with 'Hello'.
{% endif %}

只能用于字符串

逻辑真,逻辑假的约定

只有nilfalse为逻辑假,其余变量都是逻辑真,0也是真!

All values in Liquid are truthy except nil and false.

{% assign tobi = "Tobi" %}

{% if tobi %}
  This condition will always be true.
{% endif %}

空字符串也为真:

{% if settings.fp_heading %}
  <h1>{{ settings.fp_heading }}</h1>
{% endif %}

Output

<h1></h1>

数据类型

String

单引号或双引号包裹:

{% assign my_string = "Hello World!" %}

Number

支持整型和浮点型:

{% assign my_int = 25 %}
{% assign my_float = 39.756 %}

Boolean

true/false:

{% assign foo = true %}
{% assign bar = false %}

Nil

Nil is a special empty value that is returned when Liquid code has no results. It is not a string with the characters “nil”.

Array

Arrays hold lists of variables of any type.

遍历:

<!-- if site.users = "Tobi", "Laura", "Tetsuro", "Adam" -->
{% for user in site.users %}
  {{ user }}
{% endfor %}

索引:

<!-- if site.users = "Tobi", "Laura", "Tetsuro", "Adam" -->
{{ site.users[0] }}
{{ site.users[1] }}
{{ site.users[3] }}

数组不能主动创建,只能是liquid生成,可以通过split将字符串转成数组。

{% assign beatles = "John, Paul, George, Ringo" | split: ", " %}

{% for member in beatles %}
  {{ member }}
{% endfor %}

Liquid的变种

The most popular versions of Liquid that exist are Liquid, Shopify Liquid, and Jekyll Liquid.

Liquid的变种定义了自己的tag,filter等。

jekyll-templates中列出了扩充的filter。

参考

  1. liquid
  2. shopify
  3. liquid-doc
  4. jekyll-templates

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