SASS / SCSS: Interpolate variable from string / name - variables

Is it possible to get a variable by name?
I tried building the following function, but it's not working as expected...
#function variable-lookup($variable, $suffix: "") {
$value: null;
#if ($suffix != "" and global-variable-exists($variable+"-"+$suffix)) {
$value: #{$variable+"-"+$suffix};
}
#else if (global-variable-exists($variable)) {
$value: #{$variable};
}
#return $value;
}
Here's an example of how it might be used:
$primary: #000;
$primary-hover: blue;
a {
color: variable-lookup("primary", "base");
&:hover {
color: variable-lookup("primary", "hover");
}
}
The real power would come in when I want to write a bunch of context-specific, shorthand wrapper functions around this "variable-lookup" function.
Any ideas how to achieve this?

Trying to interpolate #{$variable+"-"+$suffix} to give the value primary-base and further trying to get the value of same variable name is not possible. primary-base is already a value and and can't be interpreted as a variable name. That sort of thing could lead to a lot of chaos.
For what you want to accomplish, you are better of using a map and checking for the key in that map
$colours: (
'primary': red,
'primary-base': blue
);
#function variable_lookup($colour, $suffix: '') {
$value: null;
#if ( $suffix != '' and map-has-key($colours, unquote($colour+'-'+$suffix)) ) {
$value: map-get($colours, unquote($colour+'-'+$suffix));
} #else if ( map-has-key($colours, unquote($colour)) ) {
$value: map-get($colours, unquote($colour));
}
#return $value;
}
div {
color: variable-lookup(primary, base);
}
p {
color: variable-lookup(primary);
}
This compiles to the following css
div {
color: blue; }
p {
color: red; }
Your code stored colours as variables but I used those names as keys in maps
This allowed to simulate the checking of variables in your code using the map-has-key method. If that returns true, the key exists and we can get the value which in this case would be the colour using map-get
UPDATED ANSWER
One way to address the issues you raised in your comments would be to define the variables and use them in as values in the map
$primary: #fff;
$warning: yellow;
$colours: ( primary: $primary,
primary-hover: darken($primary, 5%),
secondary: $warning,
secondary-hover: darken($warning, 5%) );
Another way would be to iterate through two lists and map colour to a style
$colours: ();
$list: primary success warning; //map primary to blue, success to green and so on
$shades: blue green yellow;
#for $i from 1 through length($list) {
$key: nth($list, $i);
$value: nth($shades, $i);
$colours: map-merge($colours, ($key: $value));
$colours: map-merge($colours, (unquote($key+'-hover'): darken($value, 5% )) );
}
#debug $colours // (primary: blue, primary-hover: #0000e6, success: green, success-hover: #006700, warning: yellow, warning-hover: #e6e600)
The variable_lookup function remains the same.
Hope this is able to help

Related

less function to generate css class

I try to do any less function which will be called to create some classes.
Here is the way I tried :
.makeCssColor{#couleur) {
.coul_#{couleur} {
background-color: fade(~"#{couleur}, 'Fonce'", 15%);
&.open, &:hover {
background-color: ~"#{couleur}, 'Fonce'";
}
.btMod {
background : url('/img/btModEvt_#{couleur}.png') left top no-repeat transparent;
}
}
}
And I try to call it to create the classes :
.makeCssColor("bleu");
.makeCssColor("rouge");
But it generate an error. I don't find the good way to do it... And it bothers me to repeat all these code for each color (there is more than these line code and more thant two colors !).
Can anyone give me a little help ? :)
[edit]
ok, thanks to your help, this code does not generate an error, but there is a mistake in the CSS file :
#marronFonce = #9d5a1e;
.makeCssColor(#couleur) {
.coul_#{couleur} {
.top {
background-color: #couleur, 'Fonce';
}
.mod {
background : url('/img/btModEvt_#{couleur}.png') left top no-repeat transparent;
}
}
}
.makeCssColor(marron);
Generate this into the css file :
.coul_marron .top{background-color:marron,'Fonce'}
.coul_marron background : url('/img/btModEvt_marron.png') left top no-repeat transparent;
So the background color isn't good :
.coul_marron .top{background-color:#9d5a1e}
.coul_marron background : url('/img/btModEvt_marron.png') left top no-repeat transparent;
I need to evaluate #couleur, 'Fonce' : #marronFonce => #9d5a1e.
I tried #{#couleur, 'Fonce'} but it doesn't works...
Fade function takes a colour and a fade percentage, in your case you are passing 2 colours. Pass them one at a time. I also made some adjustments on #couleur since i some cases they don't need to be escaped
.makeCssColor{#couleur) {
.coul_#{couleur} {
background-color: fade(#couleur, 15%), fade(Fonce, 15%);
&.open, &:hover {
background-color: #couleur, 'Fonce';
}
.btMod {
background : url('/img/btModEvt_#couleur.png') left top no-repeat transparent;
}
}
}
when you call the mixin use the below, no need to use quotes
.makeCssColor(bleu);
UPDATE - just pass it in
.makeCssColor(#couleur, #name) {
.coul_#{name} {
.top {
background-color: #couleur;
}
.mod {
background : url('/img/btModEvt_#{name}.png') left top no-repeat transparent;
}
}
}
then when you call it
.makeCssColor(#marronFonce, marron);
OR
other option is you can make a loop, it's more complicated but you can try it. I am using an example I already have on my computer
first define a variable with the colour and names
#sample:
~"0070" '#ebebe7',
~"08x2" '#00247a',
~"01k0" '#92918e';
then loops thru it
.sample-loop ( #l ) when ( #l > 0 ) {
#item: extract( #sample #l );
#code: extract( #item, 1 );
#colour: color(extract( #item, 2 ));
.ext-#{code} {
background-color: #colour;
}
.sample-loop( #l - 1 );
}
and finally call the loop to generate your classes
.sample-loop( 3 );
depending on which version of less you have, the 3 can coded so it is dynamic. If you have older version of less then you have to hard code the length of the variable, or assign the length to a variable so you can use it anywhere

Bootstrap convert spacing mixin from sass to less

I have a site running Bootstrap 3.3.7. I use less to adjust the styling. In version 4 of Bootstrap sass is introduced instead of less, and I noticed a new mixin which adds the ability to easily use predefined paddings and margins:
// Width
.w-100 { width: 100% !important; }
// Margin and Padding
.m-x-auto {
margin-right: auto !important;
margin-left: auto !important;
}
#each $prop, $abbrev in (margin: m, padding: p) {
#each $size, $lengths in $spacers {
$length-x: map-get($lengths, x);
$length-y: map-get($lengths, y);
.#{$abbrev}-a-#{$size} { #{$prop}: $length-y $length-x !important; } // a = All sides
.#{$abbrev}-t-#{$size} { #{$prop}-top: $length-y !important; }
.#{$abbrev}-r-#{$size} { #{$prop}-right: $length-x !important; }
.#{$abbrev}-b-#{$size} { #{$prop}-bottom: $length-y !important; }
.#{$abbrev}-l-#{$size} { #{$prop}-left: $length-x !important; }
// Axes
.#{$abbrev}-x-#{$size} {
#{$prop}-right: $length-x !important;
#{$prop}-left: $length-x !important;
}
.#{$abbrev}-y-#{$size} {
#{$prop}-top: $length-y !important;
#{$prop}-bottom: $length-y !important;
}
}
}
// Positioning
.pos-f-t {
position: fixed;
top: 0;
right: 0;
left: 0;
z-index: $zindex-navbar-fixed;
}
Source at GitHub
I would like to convert this mixin to less, and use it in my own Bootstrap 3.3.7 project. How would this mixin look like in less?
Less does not have any #each function or map like Sass does but even then converting this Sass code into its Less equivalent is fairly easy. All that is needed are a couple of loops each of which will mimic the two #each function in Sass and associative arrays.
In Less, we can use both comma and space as delimiters for values. So by using both of them we can achieve a behavior similar to that of maps. Even multi-level maps can be mimicked using this.
(Note: You need to know the basics of Less loops to understand this code but since you've already used Less, I assume that you are familiar with the concepts. If not, have a look at docs)
#props: margin m, padding p; /* the property and abbreviation */
#spacers: xs 10px 20px, md 20px 30px; /* the sizes, its length-x and length-y */
.loop-props(#prop-index) when (#prop-index > 0){ /* outer each loop */
#prop: extract(#props, #prop-index); /* get each prop-abbrev pair based on loop index */
#prop-name: extract(#prop, 1); /* the first value in each pair is the prop name */
#abbrev: extract(#prop, 2); /* the second value in each pair is the prop's abbrev */
/* call size loop mixin with each property name + abbreviation */
.loop-sizes(#prop-name; #abbrev; length(#spacers));
.loop-props(#prop-index - 1); /* call the next iteration of the outer each loop */
}
.loop-props(length(#props)) !important; /* initial mixin/loop call */
.loop-sizes(#prop-name; #abbrev; #size-index) when (#size-index > 0){ /* inner each */
#spacer: extract(#spacers, #size-index); /* extract each spacer value based on index */
#size: extract(#spacer, 1); /* first value in each spacer is the size */
#x: extract(#spacer, 2); /* second value is the length in X axis */
#y: extract(#spacer, 3); /* third value is the length in Y axis */
/* create the selectors and properties using interpolation */
.#{abbrev}-a-#{size} {
#{prop-name}: #y #x;
}
.#{abbrev}-t-#{size} {
#{prop-name}-top: #y;
}
.#{abbrev}-r-#{size} {
#{prop-name}-right: #x;
}
.#{abbrev}-b-#{size} {
#{prop-name}-bottom: #y;
}
.#{abbrev}-l-#{size} {
#{prop-name}-left: #x;
}
.#{abbrev}-x-#{size} {
#{prop-name}-right: #x;
#{prop-name}-left: #x;
}
.#{abbrev}-y-#{size} {
#{prop-name}-top: #y;
#{prop-name}-bottom: #y;
}
.loop-sizes(#prop-name; #abbrev; #size-index - 1); /* call next iteration */
}
As you'd have noticed, I have attached the !important to the mixin call itself instead of attaching it each property. When this is done, the Less compiler automatically attaches the !important to every property and so we needn't repeat it.

Less CSS, please explain Advanced arguments and the #rest variable to me?

Simple question: I don't understand what the Advanced arguments do in Less CSS, as per http://lesscss.org/features/#mixins-parametric-feature-advanced-arguments-and-the-rest-variable . I've battled to get my head around how it's explained there.
I understand this:
.mixin(#a: 1) {
But I don't understand the following two, where the ... is introduced:
.mixin(...) { // matches 0-N arguments
.mixin() { // matches exactly 0 arguments
.mixin(#a: 1) { // matches 0-1 arguments
.mixin(#a: 1; ...) { // matches 0-N arguments
.mixin(#a; ...) { // matches 1-N arguments
.mixin(#a; #rest...) { // #rest is bound to arguments after #a
// #arguments is bound to all arguments }
I'm learning Less because I'm very keen on bootstrap, but this puzzled me.
Thank you very much!
Well, okay you should also read http://lesscss.org/features/#mixins-parametric-feature-pattern-matching.
In Less only mixin that match the number of arguments of the caller are compiled. Notice also that when two or more mixins match, all of them are compiled into CSS.
When you mixin got one argument, like that shown below:
.mixin(#a) {}
Only callers with one argument match and will be compiled: .mixin(3); or .mixin(1) and so on. But NOT .mixin() or .mixin(1,2,3)
When you set a default value for the first argument, for instance 3, as shown below:
.mixin(#a: 3) {}
Now not only calls with 1 argument match, but also calls with zero arguments:
.mixin(#a: 3) {property: #a;}
p{ .mixin();}
outputs:
p {
property: 3;
}
Now take a look to the special ... argument, that argument matches any number of arguments. So .mixin(...) will match and get compiled the following callers .mixin(), .mixin(1) and .mixin(1,2,3,4).
When you prepend a name (including the #) to the ... argument the values will be assigned to a variable with that name:
.mixin(#listofvariables...) {
p: #listofvariables;
}
p {
.mixin(one; two; three);
}
outputs:
p {
p: one two three;
}
Notice that ... assigns the arguments to a list, which can be manipulated with the list functions too.
An mixin such as .mixin(#a; ...) is a variant of the preceding two use cases. This mixins requires a first argument set, followed by zero or any other arguments.
#arguments is a special variable that contains a list of all argument of the mixin:
.mixin(#a; #b) {p1: #arguments; p2:extract(#arguments,2); p3:#b;}
p {.mixin(1; 2);}
outputs:
p {
p1: 1 2;
p2: 2;
p3: 2;
}
So the #arguments variable can be used in any mixin and does not require an ... argument.
What would a caller for a mixin like this look like? .mixin(#a; ...)
could it be something like this: .mixin(#a,53px); ? How does it
determine where the 53px goes to?
The 53px is not assigned to a variable, but it is the second item of the #arguments list. You can get it by extract(#arguments,2).
An use case for the .mixin(#a; ...) {} can be to assign a property always when .mixin() regardless the number of arguments, example:
.mixin(#a; ...) { color: #a;}
.mixin(#a) { background-color: contrast(#a); width:100%;}
.mixin(#a; #b;) { background-color: contrast(#a); width:#b;}
div {
.mixin(red);
}
div.small {
.mixin(red,50%);
}
outputs:
div {
color: red;
background-color: #ffffff;
width: 100%;
}
div.small {
color: red;
background-color: #ffffff;
width: 50%;
}
notice that the .mixin(#a; #rest...) {} assigns 35px the first item of the #rest list. And so the following Less code:
.mixin(#color,#padding...) {
color: #color;
padding: #padding
}
div {
.mixin(red; 10px; 20px; 5px; 5px);
}
outputs:
div {
color: red;
padding: 10px 20px 5px 5px;
}

Resolving dynamic variables in LESS

I am trying to generate a number of classes in a loop based on a number of pre-defined variable snippets.
I have a variables.less document that I am importing at the top of this less file containing my color variables. I then want to generate matching classes for these, but I am unable to get less to compile the variable.
My code:
.loop-class(~"primary", ~"success", ~"info", ~"warning", ~"danger";);
.loop-class(#list, #index: 1) when (isstring(extract(#list, #index))) {
#status: extract(#list, #index);
.button-#{status} {
color: ~'#button-#{status}';
}
.loop-class(#list, (#index + 1));
}
Which compiles to:
.button-primary {
color: #button-primary;
}
.button-success {
color: #button-success;
}
etc etc
As you can see, I get the variable name to concatenate correctly, but I can not get it to resolve, so I'm guessing that LESS has already done it's variable compilation before getting to this function?
I have already tried moving the variables into this document, as well as wrapping the variables in a mixin and adding that inside the .loop-class, but neither of these seemed to help.
I also tried something like:
#status: extract(#list, #index);
#compileClass: ~'#button-#{status}';
.button-#{status} {
color: #compileClass;
}
where I am saving the variable in a another one and then referencing that, but it yields the same result.
I looked at less css calling dynamic variables from a loop and tried implementing that as follows:
.loop-class(~"primary", ~"success", ~"info", ~"warning", ~"danger";);
.define(#var) {
#fallback: ~'#button-#{var}';
}
.loop-class(#list, #index: 1) when (isstring(extract(#list, #index))) {
#status: extract(#list, #index);
.button-#{status} {
.define(#status);
color: ##fallback;
}
.loop-class(#list, (#index + 1));
}
But that gave me the error that ##button-danger (last in the index) is undefined, so it still can't resolve the variable.
Is it obvious to you guys what I'm doing wrong?
Thanks for your help!
Missing Brackets
You are missing a set of needed brackets to resolve the variable:
LESS
//imported from another file
#button-primary: cyan;
#button-success: green;
#button-info: orange;
#button-warning: yellow;
#button-danger: red;
//in your mixin file
.loop-class(~"primary", ~"success", ~"info", ~"warning", ~"danger";);
.loop-class(#list, #index: 1) when (isstring(extract(#list, #index))) {
#status: extract(#list, #index);
.button-#{status} {
color: ~'#{button-#{status}}'; /* two more brackets needed */
| |
here here
}
.loop-class(#list, (#index + 1));
}
CSS Output
.button-primary {
color: #00ffff;
}
.button-success {
color: #008000;
}
.button-info {
color: #ffa500;
}
.button-warning {
color: #ffff00;
}
.button-danger {
color: #ff0000;
}
Cleaner More Friendly Code
Also, as a matter of less cluttered and more user friendly code, you can remove your multiple string interpolations needed for the mixing call by changing isstring to iskeyword in your mixin:
.loop-class(primary, success, info, warning, danger;); /* cleaner code on call */
.loop-class(#list, #index: 1) when (iskeyword(extract(#list, #index))) {
#status: extract(#list, #index);
.button-#{status} {
color: ~'#{button-#{status}}';
}
.loop-class(#list, (#index + 1));
}

Define LESS variable from string

I'm trying to write a mixin that returns a variable for converting px to em. I've toyed with a few things, but ultimately i'd like to call a mixin and get a return value similar to SASS's functions. Based on on return values here: http://www.lesscss.org/#-return-values, I can only define a variable once as a return value. Example:
Mixin
.px-to-emz( #size, #base: #font-size-base ){
#em: round( unit( (#size / #base), ~"em" ), 3 );
}
Call it:
.foo {
font-size: #em;
.px-to-emz(10, 16px);
height: #em;
.px-to-emz(200, 16px);
}
Fine, if you want to only return one variable, but if i want to return multiple variables I need to define new variable names. Here's what i'd ideally like to do
Mixin:
.px-to-ems( #size, #var: 'em', #base: #font-size-base ){
~'#{var}': round( unit( (#size / #base), ~"em" ), 3 );
}
Call it:
.foo {
font-size: #font-size;
.px-to-ems(10, 'font-size', 16px);
height: #height;
.px-to-ems(200, 'height', 16px);
}
#1
So far the best known solution for this problem is to put each mixin call into its own scope:
.px-to-ems(#size, #base: #font-size-base) {
#-: round(unit((#size / #base), em), 3);
}
.foo {
.-() {font-size: #-; .px-to-ems( 10, 16px)}
.-() {height: #-; .px-to-ems(200, 16px)}
.-;
}
Replace #- and .- with whatever identifiers you find suitable.
#2
The other way around is to use recently added (Less 1.6.x) property interpolation feature:
.px-to-ems(#property, #size, #base: #font-size-base) {
#{property}: round(unit((#size / #base), em), 3);
}
.foo {
.px-to-ems(font-size, 10, 16px);
.px-to-ems(height, 200, 16px);
}
It's more clean than #1 if you simply need to assign the "function" result to a property.