是否在条件内设置了SASS变量？

是的，这是可能的：

$parent: true
$foo: red

@if $parent == true 
  $foo: blue

p
  color: $foo

codepen

但是，值得注意的是，您将无法使用条件检查SASS中父元素（或任何其他元素）的属性（请参阅SASS领导的这篇文章），因此parent class 在伪代码中必须被存入骚扰中$variable。

Sass Variable Scope

Sass supports two types of variables: local variables and global variables.

By default, all variables defined outside of any selector are considered global variables. That means they can be accessed from anywhere in our stylesheets. For instance, here’s a global variable:

$bg-color: green;

On the other hand, local variables are those which are declared inside a selector. Later, we’ll examine how we can customize that behavior. But for now, let’s see our first example.

Here we define a mixin and then the btn-bg-color variable within it. This is a local variable, and is therefore visible only to the code inside that mixin:

@mixin button-style {
    $btn-bg-color: lightblue;
    color: $btn-bg-color;
}

Conclusion

you can use this code to make if directive change in your variable

    $left: left;
    $right: right;

@if $dir == rtl { 
     $left: right;
    $right: left;
}
.pull-left{
   float:#{$left};
}

you can read this article Sass Variable Scope

您可以使用功能。像这样：如何动态更改文本颜色...

@function set-color($class) {
  @if ($class == red) {
    @return #f00;
  } @else {
    @return #000;
  }
}
$main-color = set-color($parent-class);