占位符Mixin SCSS / CSS

Question

I'm trying to create a mixin for placeholders in sass.

This is the mixin I've created.

@mixin placeholder ($css) {
  ::-webkit-input-placeholder {$css}
  :-moz-placeholder           {$css}
  ::-moz-placeholder          {$css}
  :-ms-input-placeholder      {$css}  
}

This is how I'd like to include the mixin:

@include placeholder(font-style:italic; color: white; font-weight:100;);

Obviously this isn't going to work because of all the colons and semi-colons that's being passed through to the mixin, but... I'd really like to just input static css and pass it through exactly like the above function.

Is this possible?

Answer 1

You're looking for the @content directive:

@mixin placeholder {
  ::-webkit-input-placeholder {@content}
  :-moz-placeholder           {@content}
  ::-moz-placeholder          {@content}
  :-ms-input-placeholder      {@content}  
}

@include placeholder {
    font-style:italic;
    color: white;
    font-weight:100;
}

SASS Reference has more information, which can be found here: http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#mixin-content

---

As of Sass 3.4, this mixin can be written like so to work both nested and unnested:

@mixin optional-at-root($sel) {
  @at-root #{if(not &, $sel, selector-append(&, $sel))} {
    @content;
  }
}

@mixin placeholder {
  @include optional-at-root('::-webkit-input-placeholder') {
    @content;
  }

  @include optional-at-root(':-moz-placeholder') {
    @content;
  }

  @include optional-at-root('::-moz-placeholder') {
    @content;
  }

  @include optional-at-root(':-ms-input-placeholder') {
    @content;
  }
}

Usage:

.foo {
  @include placeholder {
    color: green;
  }
}

@include placeholder {
  color: red;
}

Output:

.foo::-webkit-input-placeholder {
  color: green;
}
.foo:-moz-placeholder {
  color: green;
}
.foo::-moz-placeholder {
  color: green;
}
.foo:-ms-input-placeholder {
  color: green;
}

::-webkit-input-placeholder {
  color: red;
}
:-moz-placeholder {
  color: red;
}
::-moz-placeholder {
  color: red;
}
:-ms-input-placeholder {
  color: red;
}

Answer 2

I found the approach given by cimmanon and Kurt Mueller almost worked, but that I needed a parent reference (ie, I need to add the '&' prefix to each vendor prefix); like this:

@mixin placeholder {
    &::-webkit-input-placeholder {@content}
    &:-moz-placeholder           {@content}
    &::-moz-placeholder          {@content}
    &:-ms-input-placeholder      {@content}  
}

I use the mixin like this:

input {
    @include placeholder {
        font-family: $base-font-family;
        color: red;
    }
}

With the parent reference in place, then correct css gets generated, eg:

input::-webkit-input-placeholder {
    font-family: Constantia, "Lucida Bright", Lucidabright, "Lucida Serif", Lucida, "DejaVu Serif", "Liberation Serif", Georgia, serif;
    color: red;
}

Without the parent reference (&), then a space is inserted before the vendor prefix and the CSS processor ignores the declaration; that looks like this:

input::-webkit-input-placeholder {
    font-family: Constantia, "Lucida Bright", Lucidabright, "Lucida Serif", Lucida, "DejaVu Serif", "Liberation Serif", Georgia, serif;
    color: red;
}

Answer 3

This is for shorthand syntax

=placeholder
  &::-webkit-input-placeholder
    @content
  &:-moz-placeholder
    @content
  &::-moz-placeholder
    @content
  &:-ms-input-placeholder
    @content

use it like

input
  +placeholder
    color: red

Answer 4

Why not something like this?

It uses a combination of lists, iteration, and interpolation.

@mixin placeholder ($rules) {

  @each $rule in $rules {
    ::-webkit-input-placeholder,
    :-moz-placeholder,
    ::-moz-placeholder,
    :-ms-input-placeholder {
      #{nth($rule, 1)}: #{nth($rule, 2)};
    }  
  }
}

$rules: (('border', '1px solid red'),
         ('color', 'green'));

@include placeholder( $rules );

Answer 5

To avoid 'Unclosed block: CssSyntaxError' errors being thrown from sass compilers add a ';' to the end of @content.

@mixin placeholder {
   ::-webkit-input-placeholder { @content;}
   :-moz-placeholder           { @content;}
   ::-moz-placeholder          { @content;}
   :-ms-input-placeholder      { @content;}
}

Answer 6

I use exactly the same sass mixin placeholder as NoDirection wrote. I find it in sass mixins collection here and I'm very satisfied with it. There's a text that explains a mixins option more.