Generated by SassMeister.com.

placeholders-ifElse-mixins.css

.my-other-class {
  background: url(http://www.placekitten.com/200/200) no-repeat;
}

.my-class {
  background: no-kittens;
}

.my-class {
  color: green;
  font-size: 1em;
}

.my-other-class {
  color: blue;
  font-size: 1em;
}
.my-other-class:after {
  box-shadow: 2px 2px 2px black;
  border-bottom: 1px solid black;
}

placeholders-ifElse-mixins.scss

%yes-extend{
  background: url(http://www.placekitten.com/200/200) no-repeat;
}
%no-extend{
  background: no-kittens;
}
@mixin my-mixin($val1, $val2:1em, $val3:false, $val4:"oldies"){
  color: $val1;
  font-size: $val2;
  @if $val3 { @extend %yes-extend; }
  @else { @extend %no-extend; }
  &:after{
      @content;
      }
    }
.my-class{
  @include my-mixin(green);
}
.my-other-class{
    @include my-mixin(blue, $val3:true){
     box-shadow: 2px 2px 2px black;
     border-bottom: 1px solid black;
 }
}