Short description:
I'm using scss with compass, I need to know that the class exists or not.
Long Description:
What I'm trying to do is create a mixin for margin. We can pass the margin we need for all the dimensions and if will check dose any class exists for that dimensions if yes than it will extent it else will apply the dimension. For example:
I already have .mr5 class which is
.mr5 { margin-right: 5px; }
Now if the value passed in the mixin for the right dimension is 5 than I want to check if first something like
if ( exist .mr5 ) { #extend .mr5; } else { right: $dimension; }
I don't think it's possible to check for the existence of a class. I found this issue on the Sass github page, which asks for something similar, but got closed with the following comment that you can use the !optional flag for this:
The !optional flag is provided for handling classes and placeholders that may not exist.
For example:
.<your_class> {
.mr5 { margin-right: 5px; }
}
<your_selector> {
#extend .mr5 !optional;
}
}
See also the SASS reference on this flag for more info.
Related
Is there any way to customize the variables in SASS?
For example:
.m-b-{$number} {
margin-bottom: $number;
}
If I give class="m-b-50" to an element, it should take margin-bottom 50. I just want to know if it is possible with SASS.
Yes it is possible with the help of variable interpolation or variable substitution which uses #{} for variable substitution in SASS and mixins which is a block of code just like function.
Interpolation is the process of evaluating an expression or a string containing one or more variables, yielding a result in which the variables are replaced with their corresponding values.
Simple example of interpolation and set values to the css property in SASS:
$number:60;
$n: 20px;
.m-b-#{$number}{
margin-bottom: #{$number}px;
margin-top: $n;
}
To create customize class names, will use mixins:
#mixin margin-class($side, $number) {
$firstLetter: str-slice($side, 0, 1);
.m-#{$firstLetter}-#{$number}{
margin-#{$side}: #{$number}px;
}
}
$margins: (10, 20);
$sides: ("top", "right", "bottom", "left");
#mixin generate-margin(){
#each $margin in $margins{
#each $side in $sides{
#include margin-class($side, $margin);
}
}
}
#include generate-margin();
Here, generate-margin() will get executed which will call margin-class() for each $margins and $sides, and will generate the below CSS classes:
.m-t-10 {
margin-top: 10px;
}
.m-r-10 {
margin-right: 10px;
}
.m-b-10 {
margin-bottom: 10px;
}
.m-l-10 {
margin-left: 10px;
}
.m-t-20 {
margin-top: 20px;
}
.m-r-20 {
margin-right: 20px;
}
.m-b-20 {
margin-bottom: 20px;
}
.m-l-20 {
margin-left: 20px;
}
That's the one way when you want only for specific values, but if you want to create margin class for 0-20, you can loop thru 0 to 20 as shown below:
#mixin generate-margin(){
#for $margin from 1 through 20{
#each $side in $sides{
#include margin-class($side, $margin);
}
}
}
For anyone else facing this issue, here is how one can achieve this:-
#for $i from 1 through 10 {
.mb-#{$i} {
margin-bottom: #{$i}rem;
}
}
The answer is: no it is not possible. SASS is just a language to pre-generate CSS for you. There is no on-demand, dynamic creation of classes triggered by the contents of your HTML markup. When it comes time for the browser to render your HTML and apply your specified classes, it is still just using CSS. I.e. if you assign class="m-b-50" to an element, the class .m-b-50 must already be explicitly defined somewhere. As noted in the other answers, SASS can make it easier to generate a bunch of pre-defined classes but you must know which values you want to support up front.
Now, you could generate classes for some very large, all-inclusive range like -1000 to 1000 to effectively support all values you might ever try to use and it would seem to do what you wanted, but you would be forcing your users to download a larger CSS file with, most likely, a large percentage of it being unused CSS which is wasteful and can be inconsiderate in a world of paid & limited data plans.
I've been looking for the answers, but either it's not what I am really looking for, or I am not searching up properly. I want to dynamically generate the class name. Since, I use margin-top quite frequently, I have multiple classes defined with a set of rules, and I want to achieve with LESS.
I don't think is possible to create dynamic generated classes, as far as I did my research. Here is my code:
.margin-top-(#value)px {
margin-top: #value;
}
Desired Output
.margin-top-20px {
margin-top: 20px;
}
.margin-top-100px {
margin-top: 100px;
}
Just an example of what I am expecting.
Try to use mixin to achieve this.
//define the mixin
.margin-top(#value) {
.margin-top-#{value}{
margin-top:#value;
}
}
//use the mixin like this
.margin-top(20px);
U can try it here: http://winless.org/online-less-compiler
EDIT: The issue might be with a bug in dotless, which is what we're using.
I'm trying to write a Less Mixin method for writing out a lot of CSS styles. The general format of the method is:
.icon-styles(#name) {
.#{name}-icon {
background-image: url('../images/icon-#{name}.png');
display: none;
}
[data-#{name}="true"] .#{name}-icon {
display: inline-block;
}
}
Such that the icon is only visible if a containing object has the related attribute set.
However, I'm getting an error at the attribute selector saying:
Expected ']' but found '{'
Pointing to the # inside the square brackets.
I've found this post:
LESS mix variable into attribute name in an attribute selector expression
With a similar issue, and the answer suggests it might be a bug, but unfortunately the workaround doesn't work for me. I'm getting the same error on trying to write out attr inside the brackets.
I've also tried writing it like this:
[~'data-#{name}'="true"] .#{name}-icon {
Which gets rid of the error, but then #{name} is not resolved in the resulting css.
Does anyone know if there's any way to achieve what I want?
The trick is the same as suggested in LESS mix variable into attribute name in an attribute selector expression. You're just missing the main point of it: "concatenation of interpolated variables is not supported inside [attr] blocks", so you need to move out of it:
.icon-styles(#name) {
.#{name}-icon {
background-image: url('../images/icon-#{name}.png');
display: none;
}
#data-name: ~'data-#{name}';
[#{data-name}="true"] .#{name}-icon {
display: inline-block;
}
}
I've been using what I thought was a very elegant pattern for defining the styles of reusable components/widgets, using LESS. It works beautifully in LESS 1.3-, but after upgrading recently, my whole library is broken. Does anyone know a way to accomplish something like this in 1.4+?
Here's a very simple example of a component:
#componentName {
.loadMixins(){
.text() {}
.header() {}
}
.apply(){
> h3 {
// markup-specific styles
padding: 3px;
margin-bottom: 0;
// custom styles
.header();
}
> div.body, > div.popup p {
color: red;
// custom styles
.text()
}
}
}
And here's how it would be used:
.coolWidget {
#componentName.loadMixins();
// override mixins here
.text(){
color: green;
}
#componentName.apply();
}
This keeps all the markup-dependent styles abstracted from the user. I could completely change my markup and the user's styles would still work. According to the less.js changelog, 1.4.0 Beta 1 has a line "variables in mixins no longer 'leak' into their calling scope"
Is there any way around this?
Strictly speaking nested variables and mixins are still expanded into calling scope unless this scope already has those names defined.
Your example above results in a error:
SyntaxError: .header is undefined...
and it's expected as no .header() is actually defined within the .coolWidget (or anywhere else).
This can be fixed by providing "default" definitions for .text and .header somewhere inside #componentName.
For example if you modify .loadMixins() to:
.loadMixins() {
.text();
.header();
// default properties in case a caller does not provide its own:
.text() {}
.header() {}
}
then the example compiles OK and all text/header properties are overridden as expected.
I can imagine how your library may become broken because of new scope rules but this particular example you gave above does not illustrate the problem.
Is there any way to bypass LESS scoping? It's becoming annoying. Basically, I have a .text-box which defines background, border, etc. Then, in a sub-section there's a one-off change to add a margin-top: .text-box { margin-top: 10px }. Now I can't use .text-box within that section and get my original box styles; instead, all I get is the margin-top. How can I get the definition higher in the heirarchy? I suppose I could make it a function, and call that function in both places, but being that I'm using LESS, I want to do less and KISS. In PHP, you'd get to the global namespace by using / prefix, or in C++ using :: prefix.
Additionally, it doesn't seem like any definitions with the node name work for prototyping. Meaning, I can't declare it ul.products, and then use ul.categories { ul.products }. I have to omit the node name in order to re-use it. Meaning: .categories { .products }. Is this an oversight/impossibility?
Thanks
ok so let's say you've got your mixin defined, for example:
.text-box {
background: #eee;
border: 1px solid #ccc;
color: #333;
margin-top: 5px;
}
now you want to add property or modify it in some subsection, then simply do this:
div.content {
div.sub_section {
.text-box;
margin-top: 10px; // this will override 5px defined in the mixin.
}
}
...which is putting your mixin in place, and adding some property you need to add (which will override any property from the mixin itself BUT make sure the overriding property is defined AFTER the mixin is called.
it's not ideal solution, as it creates two declarations in the output css file (there will be one from mixin followed by the one you defined in .sub_section), but otherwise I don't know a solution to this problem other than defining a parametric mixin..
--
your second issue - I think that less doesn't support scope-limited definitions on purpose... if you really need to know that certain mixin is to be used by a specific tag, I would deal with it like so:
.ul_products { ... }
.ul_categories { .ul_products; ... }
ul.categories { .ul_categories; }
you can also define a bundle and call stuff from there:
#ul {
.products { ... }
.categories { ... }
}
ul.categories { #ul > categories; }
i hope i got it right.. ?