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91 lines
4.7 KiB
Markdown
91 lines
4.7 KiB
Markdown
---
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title: Sass 3.4 is Released
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author: Natalie Weizenbaum
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date: 2014-08-18 16:38 PST
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---
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We've been trying to increase the pace of Sass releases, and it looks like we've
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succeeded. A mere five months after the release of [Sass
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3.3](/blog/sass-33-is-released), we're announcing the release of Sass 3.4.0,
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codename Selective Steve. Faster releases mean fewer major features per release,
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so there are only two big new things to talk about (although there are plenty of
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little improvements you can read about in [the
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changelog](/documentation/file.SASS_CHANGELOG.html)). As the version name
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suggests, both of these features have to do with selectors.
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# Using `&` in SassScript
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"SassScript" is what we call the mini-language Sass uses for variables, property
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values, and so forth. It's mostly just CSS values, but it also supports custom
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functions, arithmetic, and so forth. In Sass 3.4, we added support for something
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new: the parent selector, `&`.
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Most Sass users will probably recognize `&` from its previous appearances in
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selectors around the world, where it's used to explicitly refer to the parent
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selector. For example, in `.parent { .child & { ... } }`, `&` refers to
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`.parent`, and this compiles to `.child .parent { ... }`.
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Now `&` works much the same way in SassScript. It refers to the same parent
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selector, but instead of just being dropped in it's exposed as a list of lists
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to make it easy for functions to inspect and manipulate it. For example, if you
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write `.foo .bar, .baz { $selector: & }`, `$selector` will be `((".foo" ".bar"),
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(".baz",))`.
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We had originally slated this feature for version 3.3, but we took it out when
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we realized [it was really hard to use these selectors in a way that didn't
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break when they contained commas](/blog/a-change-in-plans-for-sass-33).
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Because of that, we decided to delay it for a version to give us time to come up
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with its compantion feature: selector functions.
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# Selector Functions
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The problem with just exposing `&` was that the only way to use it with other
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selectors was by glomming them together as strings. This works okay in simple
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cases, but when you write `#{$selector} .child` and `$selector` is `.foo, .bar`,
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you want `.foo .child, .bar .child` but you get `.foo, .bar .child`. This is no
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good at all.
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To solve this, we added a slew of functions that use Sass's powerful built-in
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selector logic to do the right thing. For example, you can now write
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**`selector-nest(".foo, .bar", ".child")`** and get exactly what you want. These
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functions all return the same sort of nested-list representation that `&`
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uses,but they're very liberal in what they accept: anything from nested lists to
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plain old strings.
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If you want to see every selector function we thought up, check out [the
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changelog](/documentation/file.SASS_CHANGELOG.html). I do want to highlight a
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few that I'm particularly fond of, though. You've already seen
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`selector-nest()`, and **`selector-append()`** is a close relative. The
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difference between them is whitespace: `selector-nest()` adds a space between
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its selectors, where `selector-append()` doesn't. This means that
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`selector-append(".foo, .bar", "-suffix")` returns `.foo-suffix, .bar-suffix`.
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Another function I like a lot is **`selector-replace()`**. This does a
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search-and-replace of one selector within another, but it's a lot more clever
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than your basic string replace. It uses Sass's `@extend` logic to replace
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selectors *semantically*, as though every element matched by the replacement
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selector was also matched by the replaced selector. For example,
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`selector-replace(".foo.bar.baz", ".foo.baz", ".qux")` returns `.bar.qux`.
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The last really powerful function I want to draw your attention to is
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**`selector-unify()`**. This takes two selectors and returns a new selector that
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matches only elements that are matched by *both* input selectors. This is an
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operation Sass uses a lot internally, and now users can access it as well. For
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example, `selector-unify(".foo.bar", ".bar.baz")` will return `.foo.bar.baz`.
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# What's Next?
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I won't rule out the possibility of Sass 3.5 existing, but
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[Chris](https://twitter.com/chriseppstein) and I plan to focus pretty hard on
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Sass 4.0. The big feature for 4.0 is going to be `@import`, or rather the lack
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thereof. Our current import system is beginning to show its age in a major way,
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and we intend to replace it wholesale, up to and including the name. As of 4.0,
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the recommended way of pulling in other Sass files will be `@use`.
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Among the features we're planning for `@use` are two that have been widely
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requested. You'll be able to import CSS stylesheets directly into your Sass
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ones, and each stylesheet will only be run once, no matter how many times it's
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imported.
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Until then, though, run `gem update sass` and enjoy Selective Steve!
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