Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="foo">
  <input />
  <button>Search</button>
</div>

<div class="bar">
  <input />
  <button>Search</button>
</div>

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

// the searchbox object (or map)
$searchBox: (
  border: 1px solid red,
  width: 400px
);

// the corresponding searchBox mixin.
@mixin searchBox($options: $searchBox) {
  $options: map-merge( $searchBox, $options);
  display: flex;
  border: map-get($options, border);
  margin-bottom: 30px;
  padding: 10px;
  
  width: map-get($options, width);
  
  // obviously the html must be the same for all instancse
  input {
    flex: 1;
  }
  button {
    width: 80px;
  }
}

// applying OOSCSS
.foo {
  @include searchBox;
}
.bar {
  @include searchBox((
    width:300px,
    border: 5px solid green
  ));
}

SassMeister-output.css

.foo {
  display: flex;
  border: 1px solid red;
  margin-bottom: 30px;
  padding: 10px;
  width: 400px;
}

.foo input {
  flex: 1;
}

.foo button {
  width: 80px;
}

.bar {
  display: flex;
  border: 5px solid green;
  margin-bottom: 30px;
  padding: 10px;
  width: 300px;
}

.bar input {
  flex: 1;
}

.bar button {
  width: 80px;
}

SassMeister-rendered.html

<div class="foo">
  <input />
  <button>Search</button>
</div>

<div class="bar">
  <input />
  <button>Search</button>
</div>