Sass / SCSS Mixin for Clearfix - best approach?

问题:

I want to remove the clearfix class from my HTML and include a clearfix mixin in my SCSS (Rails 3.1 application). What is the best approach to this?

I am thinking of just taking the HTML 5 Boilerplate clearfix and turning it into a mixin, then @including it within the CSS for elements that need clearfixing.

Copied from HTML5 Boilerplate:

/* The Magnificent Clearfix: Updated to prevent margin-collapsing on child elements. http://j.mp/bestclearfix */
.clearfix:before, .clearfix:after { content: "\0020"; display: block; height: 0; overflow: hidden; }
.clearfix:after { clear: both; }

/* Fix clearfix: blueprintcss.lighthouseapp.com/projects/15318/tickets/5-extra-margin padding-bottom-of-page */
.clearfix { zoom: 1; }

Is there a drawback to this? Is there a better way? Can I safely remove clearfix from my HTML markup this way?

回答1:

I should probably have added - this is the solution I came up with. I am still pretty new to all this so I don't know if this will actually do the same job as setting an element's class to clearfix and using the HTML5 boilerplate code above.

@mixin clearfix {
    zoom:1;
    &:before, &:after {
        content: "\0020"; 
        display: block; 
        height: 0; 
        overflow: hidden; 
    }
    &:after {
        clear: both;
    }
}

Edit: It's best to use @extend instead of a mixin as it will produce much less CSS code. Also, it's useful to use a silent class (denoted by %) when using @extend. This prevents unexpected CSS rules and eliminates the rule you're extending if it's not being used directly.

%clearfix {
    zoom:1;
    &:before, &:after {
        content: "\0020";
        display: block;
        height: 0;
        overflow: hidden;
    }
    &:after {
        clear: both;
    }
}

#head {
    @extend %clearfix;
    padding: 45px 0 14px; margin: 0 35px 0;
    border-bottom: 1px solid $border;
}

回答2:

To achieve less code output by using @extend, define clearfix as placeholder (here just for modern browsers w/o IE 6+7):

Sass code:

%clearfix {
    &:after {
        content: " ";
        display: block;
        clear: both;
    }
}

/* Use above defined placeholder in the selector(s) of your needs via @extend: */
#container {
    position: relative;
    min-width: 42.5em;
    @extend %clearfix;
}

CSS output will be:

#container:after {
    content: " ";
    display: block;
    clear: both;
}
#container {
    position: relative;
    min-width: 42.5em;
}

回答3:

// source http://www.alistapart.com/articles/getting-started-with-sass/
// http://nicolasgallagher.com/micro-clearfix-hack/

    @mixin clearfix {
     // For modern browsers
      &:before,
      &:after {
        content:" ";
        display:table;
      }

      &:after {
        clear:both;
      }

      // For IE 6/7 (trigger hasLayout)
      & {
        *zoom:1;
      }
    }

回答4:

Why not use the Compass framework? It already provides mixins for clearfix among a host of other useful mixins and utilities. It's always better to look for existing tools rather than to have to maintain additional code yourself.