How to extend a class from a CSS file in Sass? - css

I have a style library with the general styling for my project. This library is packed into one library.css file. In this library, I have a class a.
In one of my scss stylesheets I'd like to extend this calss a from library.css:
#import 'library.css';
.b {
#extend .a
}
When I do this, I'm told that class a was not found in library.css.
Is there any way to extend a class from a CSS stylesheet?

When you add an #import at-rule to your Sass code, you need to be careful what you wish to achieve. #import is actually valid CSS, so Sass needs to evaluate and figure out your intentions here. Sass extends the CSS #import rule and does not recreate it. According to the documentation:
#import takes a filename to import. By default, it looks for a Sass file to import directly, but there are a few circumstances under which it will compile to a CSS #import rule:
If the file's extension is .css.
If the filename begins with http://.
If the filename is a url().
If the #import has any media queries.
As a result, if you put the .css extension after the filename in an #import at-rule, Sass will just output this line of valid CSS code. You can test this by removing your #extend directive, which will make your code compile. You will see that the entire output file is this:
#import 'library.css';
Sass is not going to follow that CSS file and make it's contents available to the #extend directive.
What you could do is remove the file extension from your #import at-rule.
#import 'library';
.b {
#extend .a
}
However, this will actually output the entire contents of the file library.css into your CSS file that this Sass file compiles to, which I am assuming is not your goal.
To fix that, you could create a partial Sass file that contains placeholder selectors.
%a {
color: red;
}
The good thing about placeholder selectors is that they have no output of their own. According to the documentation:
On their own, without any use of #extend, rulesets that use placeholder selectors will not be rendered to CSS.
Their importance and usefulness is detailed on this page.
Import the partial Sass file in your Sass stylesheet and use the #extend directive like this:
.b {
#extend %a;
}
And to make sure your library.css file is consistent, convert it into Sass, import the same partial file on top of it containing your placeholder selectors and simply use the #extend directive inside .a selector as well.
#import 'placeholders';
.a {
#extend %a;
}

Related

Loading padding/margin from different SCSS file

Is it possible to load property from class from different scss file? This side scss file is imported to main scss file. All properties are inherited, but margins, paddings, font styles not. Browser is not willing to load these properites. Are there any rules with extend?
Side scss file:
.section-headline {
font-size: em(30);
font-weight: 700;
line-height: auto;
color: $main-col-text;
margin-bottom: em(20);
}
Main scss file:
.i-headline {
#extend .section-headline;
}
In SASS you can declare classes in one file and import them into another without any problem, just make sure your import is done properly. And yes you can use #extend to access the rules of your imported selector.
Also try display: inline-block; and see if your margin/padding are working. Maybe you were trying to apply them to an inline element.
Does your em() function is imported somewhere ?
I found the problem. I have one scss file where are imported all scss sub-files. It looks like this:
#import 'gClass';
#import 'buttons';
#import 'general';
#import 'mixins';
#import 'typography';
#import 'pages/home';
In sub-file gClass is my class .section-headline. In pages/home is scss code with i-headline class. I tried to copy .section-headline to main scss file mentioned upper. In this case it works, but if i try to have .section-headline in gClass file, it doesnt.

Angular 2 extend a style from styles.scss

In Angular 2, I have a CSS class in my styles.scss file:
.FirstClass {
}
I'm trying to extend this class in a component's .SCSS file (eg.: MyComponent.scss) like:
.SecondClass {
#extend .FirstClass;
}
I'm getting an error that says .FirstClass is not found. Do I assume correctly that class and style in styles.scss can be globally referred? Please help me in this.
If you have any file, and you want to use one of its classes in another file, you have to import it first.
styles.scss
.FirstClass{}
MyComponent.scss
#import 'styles.scss'
.SecondClass{
#extend .FirstClass;
}
SCSS is compile to CSS, hence, if you need to make any changes in the file itself that not related plain css, you have to take it into consideration.

How to import specified classes from CSS file instead of everything

I'm trying to import some classes from a CSS file like bootstrap.css to my site.scss SASS file, not all of them. The problem with following code is that I get all bootstrap classes in my compiled site.css file:
site.scss
#import "bootstrap";
.my-div-md-6
{
/*some other styles*/
#extend .col-md-6;
}
On the other hand, It is possible to do this with LESS by importing bootstrap.css as reference using this code:
site.less
#import (less, reference) "bootstrap.css";
.my-div-md-6{
/*some other styles*/
&:extend(.col-md-6);
}
The compiled output of LESS is very light as below:
site.css
.my-div-md-6 {
position: relative;
min-height: 1px;
padding-right: 15px;
padding-left: 15px;
}
#media (min-width: 992px) {
.my-div-md-6 {
float: left;
}
.my-div-md-6 {
width: 50%;
}
}
.my-div-md-6 {
/*some other styles*/
}
Is it possible to achieve this with SASS? If yes, giving a quick example would help.
Unfortunately, there is not simple answer and at the time of writing this, Ruby Sass does not natively support the LESS import (reference) feature.
TLDR; Suggestions:
use uncss or postcss to remove the compiled css from file before finalising stylesheet.
if you can, use mixins and placeholder classes as a rewrite of the scss file, but this is the MOST time consuming.
import "file" as partial such that file="_file.scss" and #extend .class if you absolutely have to, (manual method but suppose it'll work)
UNCSS
You can use uncss as a package from npm to remove the compiled css (I know this isn't efficient, but if you had to use SASS), then you'd remove the chaff that's generated from the example bootstrap import.
HOW?
QUOTE: SO-Answer-Joesph
How? The process by which UnCSS removes the unused rules is as follows:
The HTML files are loaded by PhantomJS and JavaScript is executed.
Used stylesheets are extracted from the resulting HTML.
The stylesheets are concatenated and the rules are parsed by css-parse.
document.querySelector filters out selectors that are not found in the HTML files.
The remaining rules are converted back to CSS.
So yes, it removes selectors not in the DOM at runtime. If you have dynamically added selectors, you can make uncss ignore them by commenting: /* uncss:ignore */ before them, e.g...
MAKE SURE YOU ADD THE MEDIA OPTION IN UNCSS
REF: SO-Answer-Deksden
SASS Background research:
Summarising above:
nex3: one of the core leads for sass, has been at google and working on dart. They released dart-sass (unstable release) as a rewrite in favour to replace and improve upon ruby sass. This is interesting as this rewrite also explains the lack of feature development in Ruby Sass as well as the need for a rewrite. Since a core contributor of a ruby sass port: i.e. libsass (C++ implementation of ruby-sass) left the libsass team, it brings a further impetus to improve on sass performance.
Credit:
Joesph
Deksden

Can I use css-classes as a mixin in a less-file?

In my style.less I'd like to define, that all elements with the class .element nested within an element of the class .group have the same properties of the bootstrap-class .col-sm-6.
Unfortunately I can't directly add the class .col-sm-6 to the elements.
In that project, bootstrap is available in the folder tapestry5/bootstrap/css/bootstrap-darkly.css releative to my style.less. (How) Can I also use CSS-classes as mixins within my style.css? I tried:
#import (reference) "tapestry5/bootstrap/css/bootstrap-darkly.css";
.group .element {
.col-sm-6;
}
Unformtunately I get a Less4J Exception:
Could not find mixin named ".col-sm-6". - line 4 - position 3
Is it impossible to use CSS as mixins, or is something wrong with my syntax?
If you change the css file you have available to less file ending and import it (as all CSS is valid LESS). The less compiler will be able to find and use .col-sm-6 as a mixin.
#import (reference) "tapestry5/bootstrap/css/bootstrap-darkly.less";
.group .element {
.col-sm-6;
}
If you're going to be using the Bootstrap LESS, you may as well make use of their mixins instead of their CSS. As seven-phases-max suggested in his comment, you can use make-*-column instead of using the CSS classes.
You'd do this instead:
.group .element {
.make-sm-column(6);
}

Import css/scss file into a class

I have a problem. I'm using vaadin inside liferay. I've successfully written a fully responsive (yeah, tables too) theme for vaadin, based on bootstrap. Now I'm importing it to liferay. Everything went fine 'till I needed to upgrade Liferay, where their new responsive theme is using same classes name as bootstrap, but with different behaviour (sad, very sad face).
The solution I've thought so far is to apply a class to the vaadin compiled css, like:
.daVaadinTheme {
#import bootstrap.css;
}
so the content will be compiled like:
.daVaadinTheme h1.insideTheFile{
}
.daVaadinTheme h2.insideTheFile{
}
But, as you may figured out, is not obviously working.
Do you have any solution?
Read carefully! This is NOT a duplicate of the answer you've posted. I'm trying to import a CSS file inside a CSS/SCSS class of another file, like the example I've written above. My problem is not to simply import a CSS file inside another one...
SOLUTION: (kudos to Mathias Jørgensen)
using #import from another scss file:
in test.scss:
.daVaadinTheme{
#import "bootstrap.scss";
}
Name your inner file with an underscore, and ending in scss. .Yes, even if it's plain css, i.e. foo.css → _foo.scss
Have an outer File like so:
#main .content { // if that's, where you want them to rule only
#import 'foo';
}
Reasons:
import only works with scss
underscore-files are glady skipped by sass (also as in gulp.src(<some wildcards).sass())
if you have no influence in your repo about the css filename whatsoever. or it's a major pain on upgrades, consider using a symbolic link under an .scss extension...
You need move your code into mixin:
// botstrap.scss
#mixin bootstrap {
h1.insideTheFile{
}
h2.insideTheFile{
}
}
Then, you can import normal:
// test.scss
#import "bootstrap"; // No extension
#include bootstrap; // The name of "mixin"
or with context:
// test.scss
#import "bootstrap"; // No extension
.daVaadinTheme {
#include bootstrap; // The name of "mixin"
}
If you want to add certain styles to a class using sass/scss I think what you're looking for is
.myClass { #import bootstrap.css; }

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