less-css — is it possible to get a parent's pa

问题:

Is it possible to get a parent's parent?

I tried & & { } but that didn't work.

I'm trying to style a child element based on it's grandparent.

回答1:

Depends on Code Structure, and may Require Some Repetition of Code

You cannot do it directly in most cases (see second example for exception).

If Grandparent is an element

This requires some repetition, but does allow for the grandparent to not be the outermost wrapper (so there could be a great grandparent).

LESS

grandparent {  
  /* grandparent styles */
  parent {
    /* parent styles */
    child {
      /* child styles */
    }
  }
  &.specialGrandpa {
    child {
      /* child styles with special Grandpa */
    }
  }
  &.specialGrandma {
    child {
      /* child styles with special Grandma*/
    }
  }
}

CSS Output

grandparent {
  /* grandparent styles */    
}
grandparent parent {
  /* parent styles */    
}
grandparent parent child {
  /* child styles */    
}
grandparent.specialGrandpa child {
  /* child styles with special Grandpa */    
}
grandparent.specialGrandma child {
  /* child styles with special Grandma*/    
}

If Grandparent is a class, ID, etc., and is the outermost wrapper

No repetition involved here, but you cannot have a great grandparent in the mix. Also this is only for LESS 1.3.1+ version (earlier version incorrectly add a space):

LESS

.grandparent {  
  /* grandparent styles */
  .parent {
    /* parent styles */
    .child {
      /* child styles */
      .specialGrandparent& {
          /* child styles with special grandparent*/
      }
    }
  }
}

CSS Output

.grandparent {
  /* grandparent styles */    
}
.grandparent .parent {
  /* parent styles */   
}
.grandparent .parent .child {
  /* child styles */    
}
.specialGrandparent.grandparent .parent .child {
  /* child styles with special grandparent*/   
}

This code works by appending to the "front" of the grandparent selector, so that is why the grandparent must be a class, ID, or other selector itself.

Addendum

Based on comment about desire to have a red background when the span is empty. This does not put the background on the parent, but "fakes" it using the child.

span:empty:after {
    content: '';
    position: absolute;
    top: -1px;
    right: -10px;
    left: -1px;
    bottom: -10px;
    display: block;
    background-color: red;
    z-index: -1;
}

回答2:

You cannot traverse arbitrarily up the DOM with less selectors. Use javascript instead.

The & in less stands for declared selector one level up. A shortcut for already defined rule. As opposed to what you allegedly seek.

回答3:

According to LESS's parent selectors feature, it's possible to change selector order by putting the & after the items in your nest, thereby accessing the item's parent's parent.

LESS code:

span {
  color:red;
  h6 & {
    color:white;
    div & {
      color:blue;
    }
  }
}

CSS result:

span {
  color: red;
}
h6 span {
  color: white;
}
div h6 span {
  color: blue;
}

回答4:

You can use a mixin, then you can pass variables to it based on grandparent selector specifics.

Example:

ul {
    .color-links(@color) {
        li a { // any link inside a child li
            color: @color;
        }
    }
    &.red {
        .color-links(#ff0000);
    }
    &.green {
        .color-links(#00ff00);
    }
}