Sass Directives and Maps

Written by Michael Lee on April 29, 2014

I’ve started playing around with Sass Directives and Maps; which the latter was recently introduced in Sass 3.3. If you’re familiar with languages like Javascript or Ruby, a Sass Map is the equivalent of a Hash; they store key/value pairs.

One of the first things I did when I discovered Sass Directives and Maps were to convert my color variables into a map and use a loop to quickly generate utility style blocks in the manner of OOCSS.

Here’s an example of going from using variables to using a Map and a loop.

Before:

$black: #000;
$white: #fff;
$red: #eb6f60;
$blue: #45aee7;
$purple: #837abd;

.bg--black{ background-color: $black; }
.bg--white{ background-color: $white; }
.bg--red{ background-color: $red; }
.bg--blue{ background-color: $blue; }
.bg--purple{ background-color: $purple; }

After:

$colors:(
  black: #000,
  white: #fff,
  red: #eb6f60,
  blue: #45aee7,
  purple: #837abd,
);

@each $color, $value in $colors{
  .bg--#{$color}{ background-color: #{$value}; }
}

Both would create this final CSS:

.bg--black{ background-color: #000; }
.bg--white{ background-color: #fff; }
.bg--red{ background-color: #eb6f60; }
.bg--blue{ background-color: #45aee7; }
.bg--purple{ background-color: #837abd; }

Awesome right? Less code and you won’t miss any colors you define in the map. But what if you want to use a color value from the map?

It’d look something like this:

.button--blue{
  border: 1px solid map-get($colors, blue);
}

The map-get function with two parameters seem a bit verbose when prior to maps I just called $variableName.

At first, I thought I could just use another loop to create variables on the fly.

@each $color, $value in $colors{
  $#{$color}: $value;
}

But it turns out that this is invalid and won’t compile at all. John Long from The Sass Way confirmed this as well.

After some conversations with my buddy, Joel. He suggested I write out the variables again, then create it’s duplicate key but use the variable value to create the map.

$black: #000;
$white: #fff;
$red: #eb6f60;
$blue: #45aee7;
$purple: #837abd;

$colors:(
  black: $black,
  white: $white,
  red: $red,
  blue: $blue,
  purple: $purple,
);

This way, I can update any values for a variable I created and the map would update and generate my utilities accordingly. I can still use $variableName instead of map-get($map, value) for use in style blocks.

This feels a bit cumbersome to maintain but with this solution I can still use variable names and I get the benefits of Maps and Sass Directives for creating OOCSS utilities.

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