sass-site/source/documentation/at-rules/forward.html.md.erb
Natalie Weizenbaum d8c3238c79
Document @forward (#368)
Closes #362
2019-09-06 14:13:51 -07:00

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---
title: "@forward"
introduction: >
The `@forward` rule loads a Sass stylesheet and makes its [mixins](mixin),
[functions](function), and [variables](../variables) available when your
stylesheet is loaded with the [`@use` rule](use). It makes it possible to
organize Sass libraries across many files, while allowing their users to load
a single entrypoint file.
---
The rule is written `@forward "<url>"`. It loads the module at the given URL
just like `@use`, but it makes the [public][] members of the loaded module
available to users of your module as though they were defined directly in your
module. Those members aren't available in your module, though—if you want that,
you'll need to write a `@use` rule as well. Don't worry, it'll only load the
module once!
[public]: use#private-members
<% fun_fact do %>
The `@forward` rule acts just like `@use` when it comes to a module's CSS.
Styles from a forwarded module will be included in the compiled CSS output,
and the module with the `@forward` can [extend][] it, even if it isn't also
`@use`d.
[extend]: extend
<% end %>
<% example do %>
// src/_list.scss
@mixin list-reset {
margin: 0;
padding: 0;
list-style: none;
}
---
// bootstrap.scss
@forward "src/list";
---
// styles.scss
@use "bootstrap";
li {
@include bootstrap.list-reset;
}
===
// src/_list.sass
@mixin list-reset
margin: 0
padding: 0
list-style: none
---
// bootstrap.sass
@forward "src/list"
---
// styles.sass
@use "bootstrap"
li
@include bootstrap.list-reset
===
li {
margin: 0;
padding: 0;
list-style: none;
}
<% end %>
## Adding a Prefix
Because module members are usually used with [a namespace][], short and simple
names are usually the most readable option. But those names might not make sense
outside the module they're defined in, so `@forward` has the option of adding an
extra prefix to all the members it forwards.
This is written `@forward "<url>" as <prefix>-*`, and it adds the given prefix
to the beginning of every mixin, function, and variable name forwarded by the
module. For example, if the module defines a member named `reset` and it's
forwarded `as list-*`, downstream stylesheets will refer to it as `list-reset`.
[a namespace]: use#loading-members
<% example do %>
// src/_list.scss
@mixin reset {
margin: 0;
padding: 0;
list-style: none;
}
---
// bootstrap.scss
@forward "src/list" as list-*;
---
// styles.scss
@use "bootstrap";
li {
@include bootstrap.list-reset;
}
===
// src/_list.sass
@mixin reset
margin: 0
padding: 0
list-style: none
---
// bootstrap.sass
@forward "src/list" as list-*
---
// styles.sass
@use "bootstrap"
li
@include bootstrap.list-reset
===
li {
margin: 0;
padding: 0;
list-style: none;
}
<% end %>
## Controlling Visibility
Sometimes, you don't want to forward *every* member from a module. You may want
to keep some members private so that only your package can use them, or you may
want to require your users to load some members a different way. You can control
exactly which members get forwarded by writing `@forward "<url>" hide
<members...>` or `@forward "<url>" show <members...>`.
The `hide` form means that the listed members shouldn't be forwarded, but
everything else should. The `show` form means that *only* the named members
should be forwarded. In both forms, you list the names of mixins, functions, or
variables (including the `$`).
<% example(autogen_css: false) do %>
// src/_list.scss
$horizontal-list-gap: 2em;
@mixin list-reset {
margin: 0;
padding: 0;
list-style: none;
}
@mixin list-horizontal {
@include reset;
li {
display: inline-block;
margin: {
left: -2px;
right: $horizontal-list-gap;
}
}
}
---
// bootstrap.scss
@forward "src/list" hide list-reset, $horizontal-list-gap;
===
// src/_list.sass
$horizontal-list-gap: 2em
@mixin list-reset
margin: 0
padding: 0
list-style: none
@mixin list-horizontal
@include reset
li
display: inline-block
margin:
left: -2px
right: $horizontal-list-gap
---
// bootstrap.sass
@forward "src/list" hide list-reset, $horizontal-list-gap
<% end %>