diff --git a/docs/_docs/includes.md b/docs/_docs/includes.md new file mode 100644 index 00000000..dceece77 --- /dev/null +++ b/docs/_docs/includes.md @@ -0,0 +1,175 @@ +--- +layout: docs +title: Includes +permalink: /docs/includes/ +--- + +The `include` tag allows you to include the content from another file stored in the `_includes` folder: + +```liquid +{% raw %}{% include footer.html %}{% endraw %} +``` + +Jekyll will look for the referenced file (in this case, `footer.html`) in the `_includes` directory at the root of your source directory and insert its contents. + +### Including files relative to another file + +You can choose to include file fragments relative to the current file by using the `include_relative` tag: + +```liquid +{% raw %}{% include_relative somedir/footer.html %}{% endraw %} +``` + +You won't need to place your included content within the `_includes` directory. Instead, +the inclusion is specifically relative to the file where the tag is being used. For example, +if `_posts/2014-09-03-my-file.markdown` uses the `include_relative` tag, the included file +must be within the `_posts` directory or one of its subdirectories. + +Note that you cannot use the `../` syntax to specify an include location that refers to a higher-level directory. + +All the other capabilities of the `include` tag are available to the `include_relative` tag, +such as variables. + +### Using variables names for the include file + +The name of the file you want to embed can be specified as a variable instead of an actual file name. For example, suppose you defined a variable in your page's frontmatter like this: + +```yaml +--- +title: My page +my_variable: footer_company_a.html +--- +``` + +You could then reference that variable in your include: + +```liquid +{% raw %}{% include {{page.my_variable}} %}{% endraw %} +``` + +In this example, the include would insert the file `footer_company_a.html` from the `_includes/footer_company_a.html` directory. + +### Passing parameters to includes + +You can also pass parameters to an include. For example, suppose you have a file called `note.html` in your `_includes` folder that contains this formatting: + +```liquid +{% raw %}{% endraw %} +``` + +The {% raw %}`{{include.content}}`{% endraw %} is a parameter gets populated when you call the include and specify a value for that parameter, like this: + +```liquid +{% raw %}{% include note.html content="This is my sample note." %} {% endraw %} +``` + +The value of `content` (which is `This is my sample note`) will be inserted into the {% raw %}`{{include.content}}`{% endraw %} parameter. + +Passing parameters to includes is especially helpful when you want to hide away complex formatting from your Markdown content. + +For example, suppose you have a special image syntax with complex formatting, and you don't want your authors to remember the complex formatting. As a result, you decide to simplify the formatting by using an include with parameters. Here's an example of the special image syntax you want to populate with an include: + +```html +
Jekyll logo
+This is the Jekyll logo
+``` + +You could templatize this content in your include and make each value available as a parameter, like this: + +```liquid +{% raw %}
{{include.caption}} +
{% endraw %} +``` + +This include contains 5 parameters: + +* `url` +* `max-width` +* `file` +* `alt` +* `caption` + +You could also use `if` tags to safeguard scenarios where either the parameter is optional or where the author doesn't include the parameter: + +```liquid +{% raw %}
{% if {{include.url}} %} +{% endif %}{% if {{include.url}} %}{% endif %} +{% if {{include.caption}} %}
{{include.caption}} +
{% endif %}
{% endraw %} +``` + +In this example, `{% raw %}if {{include.url}}{% endraw %}` will include the `url` only if the `url` parameter is specified in the include. You could also create default values using [Liquid's default filter](https://help.shopify.com/themes/liquid/filters/additional-filters#default). + +Here's an example that passes all the parameters to this include (the include file is named `image.html`): + +```liquid +{% raw %}{% include image.html url="http://jekyllrb.com" +max-width="200px" file="logo.png" alt="Jekyll logo" +caption="This is the Jekyll logo." %} {% endraw %} +``` + +The result is the original HTML code shown earlier. + +You can create includes that act as templates for a variety of uses — inserting audio or video clips, alerts, special formatting, and more. + +However, note that you should avoid using too many includes, as this will slow down the build time of your site. For example, don't use includes every time you insert an image. (The above technique shows a use case for special images.) + +### Passing parameter variables to includes + +Suppose the parameter you want to pass to the include is a variable rather than a string. For example, you might be using {% raw %}`{{site.product_name}}`{% endraw %} to refer to every instance of your product rather than the actual hard-coded name. (In this case, your `_config.yml` file would have a key called `product_name` with a value of your product's name.) + +The string you pass to your include parameter can't contain curly braces. For example, you can't pass a parameter that contains this: {% raw %}`"The latest version of {{site.product_name}} is now available."`{% endraw %} + +If you want to include this variable in your parameter that you pass to an include, you need to store the entire parameter as a variable before passing it to the include. You can use `capture` tags to create the variable: + +```liquid +{% raw %}{% capture download_note %}The latest version of +{{site.product_name}} is now available.{% endcapture %}{% endraw %} +``` + +Then pass this captured variable into the parameter for the include. Omit the quotation marks around the parameter content because it's no longer a string (it's a variable): + +```liquid +{% raw %}{% include note.html content=download_note %}{% endraw %} +``` + +### Passing references to YAML files as parameter values + +Instead of passing string variables to the include, you can pass a reference to a YAML data file stored in the `_data` folder. + +Here's an example. In the `_data` folder, suppose you have a YAML file called `profiles.yml`. Its content looks like this: + +```yaml +- name: John Doe + login_age: old + image: johndoe.jpg + +- name: Jane Doe + login_age: new + image: janedoe.jpg +``` + +In the `_includes` folder, assume you have a file called `spotlight.html` with this code: + +```liquid +{% raw %}{% for person in {{include.participants}} %} +{% if person.login_age == "new" %} +{{person.name}} +{% endif %} +{% endfor %}{% endraw %} +``` + +Now when you insert the `spotlight.html` include file, you can submit the YAML file as a parameter: + +``` +{% raw %}{% include spotlight.html participants=site.data.profiles %}{% endraw %} +``` + +In this instance, `site.data.profiles` gets inserted in place of {% raw %}`{{include.participants}}`{% endraw %} in the include, and the Liquid logic processes. The result will be `Jane Doe`.