SCSS - Extending Classes Within Media Queries

If you have used SASS for some time you will know that if you are within a media query and try to extend a class that is outside of the media query you will get an error. Let’s find a way around it.

The problem

If you do this:

.small-btn {
  padding: 5px;
  &:hover {
    background-color: white;
    color:black;
  }
}

@media (max-width: 768px) {
  button {
    @extend .small-btn;
  }
}

You will get this:

Error: You may not @extend an outer selector from within @media.
       You may only @extend selectors within the same directive.
       From "@extend .small-btn" on line 7 of src/scss/main.scss

This is very annoying and can be a hindrance when your are trying to do some really interesting things in responsive websites. To go around this limitation we must find a way to include a collection of rules and sub-rules within a class inside a media query.

A way around it

The answer we are looking for is a @mixin. With a @mixin we can import all the rules that we want very easily. What we would have to do is to put the code from the class we want to extend inside of a @mixin instead of inside the class itself. Then both the class and the section inside the media query will import the @mixin functionality.

Here is how it could look like:

@mixin small-btn-mixin() {
  padding: 5px;
  &:hover {
    background-color: white;
    color:black;
  }
}

.small-btn {
  @include small-btn-mixin();
}

@media (max-width: 768px) {
  button {
    @include small-btn-mixin();
  }
}

A limitation of this method is that you have to explicitly create a mixin for every class you want to extend within a media query. With the ‘@extend’ keyword, on the other hand, you can extend any class on the fly without further complications. Also, be mindful that with @extend SASS would integrate all instances where there is code associated with this class, while this method will only include what was declared within the @mixin.

Although not perfect, this method does provide us with an alternative to having to repeat code.


TL;DR

  • Instead of extending, put the code you want to reproduce inside a @mixin.
 @mixin small-btn-mixin() {
   padding: 5px;
   &:hover {
     background-color: white;
     color:black;
   }
 }

 @media (max-width: 768px) {
   button {
     @include small-btn-mixin();
   }
 }

Written on April 2, 2016