在LESS中生成选择器列表

Question

现场演示:http://codepen.io/KenPowers/pen/Ddfqh

考虑以下LESS代码:

// Hide all list items by default and make internal labels have pointer cursors
li {
  display: none;
  label {
    cursor: pointer;
  }
}

// This function generates selectors and corresponding css
.gen (@tag) {
  @sel: ~"#@{tag}:checked";
  @{sel} {
    & ~ ul > li[data-index~=@{tag}] {
      display: list-item;
    }
    & ~ ul > li > label[for=@{tag}] {
      color: red;
    }
  }
}

// Generate required selectors and css
.gen("foo");
.gen("bar");
.gen("baz");

它生成以下CSS:

li {
  display: none;
}
li label {
  cursor: pointer;
}
#foo:checked ~ ul > li[data-index~="foo"] {
  display: list-item;
}
#foo:checked ~ ul > li > label[for="foo"] {
  color: red;
}
#bar:checked ~ ul > li[data-index~="bar"] {
  display: list-item;
}
#bar:checked ~ ul > li > label[for="bar"] {
  color: red;
}
#baz:checked ~ ul > li[data-index~="baz"] {
  display: list-item;
}
#baz:checked ~ ul > li > label[for="baz"] {
  color: red;
}

但是,更加压缩的输出可能如下所示:

li {
  display: none;
}
li label {
  cursor: pointer;
}
#foo:checked ~ ul > li[data-index~="foo"],
#bar:checked ~ ul > li[data-index~="bar"],
#baz:checked ~ ul > li[data-index~="baz"] {
  display: list-item;
}
#foo:checked ~ ul > li > label[for="foo"],
#bar:checked ~ ul > li > label[for="bar"],
#baz:checked ~ ul > li > label[for="baz"] {
  color: red;
}

有没有办法可以修改原始LESS来生成第二个CSS列表？

Answer 1

在Less 1.4.0+中,您可以:extend使用占位符类:

.dp-list-item {
  display: list-item;
}
.label-color {
  color: red;
}

// This function generates selectors and corresponding css
.gen (@tag) {
  @sel: ~"#@{tag}:checked ~ ul > li";
  @{sel} {
    &[data-index~=@{tag}]:extend(.dp-list-item){}
    & > label[for=@{tag}]:extend(.label-color){}
  }
}

// Generate required selectors and css
.gen("foo");
.gen("bar");
.gen("baz");

叉笔

生成的CSS:

.dp-list-item,
#foo:checked ~ ul > li[data-index~="foo"],
#bar:checked ~ ul > li[data-index~="bar"],
#baz:checked ~ ul > li[data-index~="baz"] {
  display: list-item;
}
.label-color,
#foo:checked ~ ul > li > label[for="foo"],
#bar:checked ~ ul > li > label[for="bar"],
#baz:checked ~ ul > li > label[for="baz"] {
  color: red;
}

正如您所看到的,唯一的缺点是我用作占位符的两个类都将在生成的CSS中.我相信这不能解决,直到Less实现类似于Sass' 占位符选择器的东西.

PS.li为简洁起见,我省略了不属于mixin 的全局规则.

根据OP请求,这里是一个.scss等效的Sass(带语法):

//placeholder selectors
%dp-list-item {
  display: list-item;
}
%label-color {
  color: red;
}

// This function generates selectors and corresponding css
@mixin gen($tag) {
  ##{$tag}:checked ~ ul > li {
    &[data-index~=#{$tag}] {
      @extend %dp-list-item;
    }
    & > label[for=#{$tag}] {
      @extend %label-color;
    }
  }
}

// Generate required selectors and css
@each $item in (foo bar baz) {
  @include gen($item);
}

演示

生成的CSS:

#foo:checked ~ ul > li[data-index~=foo], #bar:checked ~ ul > li[data-index~=bar], #baz:checked ~ ul > li[data-index~=baz] {
  display: list-item;
}

#foo:checked ~ ul > li > label[for=foo], #bar:checked ~ ul > li > label[for=bar], #baz:checked ~ ul > li > label[for=baz] {
  color: red;
}

你可以看到,与Less相比,Sass的语法相当冗长.Sass还有一些很好的功能,比如控制指令和优秀的插值,我已在上面的例子中应用过.