Using "each loop variables" inside if statement in SASS - if-statement

Question

I am trying to generate a bunch of styles through an each loop in SASS. The styles should only be generated, if the variable the each loop is looking at right now is set.
I tried different variable "styles", e.g.: $use-#{$type}, but I'm kinda lost. Even tried to do it with a function, but it seems like functions can not access the variables of loops.
$typo: (t1, t2);
$use-t1: 1; $t1-color: black;
$use-t2: 1; $t2-color: black;
#each $type in $typo{
#if $#{use-$type} == 1{
.#{$type}{
color: $#{$type}-color;
}
}
}
I would expect the variables in the first round of the each loop to be:
$#{use-$type} -> $use-t1 -> 1
$#{$type}-color -> $t1-color -> black
But both throw "Expected identifier." or "Unknown variable", depending on how I try it.

Answer 1

You can't reference a variable using interpolation – in your case $#{$type}-color.
I would recommend you to use a map instead – like:
$map: (
t1: (use: 1, color: black),
t2: (use: 2, color: white)
);
#each $key, $value in $map {
#if map-get($value, use) == 1 {
.#{$key} { color: map-get($value, color); }
}
}
// output
.t1 { color: black; }
As a side note it's worth knowing Sass will not print properties with null values or classes without properties – why you can do the above without checking use
$map: (
t1: (color: black),
t2: (color: null) // no color => no prop => empty class => nothing printed
);
#each $key, $value in $map {
.#{$key} { color: map-get($value, color); }
}
// output
.t1 { color: black; }