Is it possible to use CSS Function from a Less variable? - css

Question

What I basically want to do
#gradientType: radial-gradient;
background: #gradientType(to bottom, ...)
I want to put a CSS Function, a gradient in this case (btw: are these called functions? I'm not sure) in a Less variable and call it later with the variable like #variable()?
Why? Maintainability!
I have a file variables.less where I want to change to gradient (ie) for a couple of places on the fly.
So instead of
.a { background: linear-gradient(..) }
.b { background: linear-gradient(..) }
.c { background: linear-gradient(..) }
I would have something like
.a { background: #myGradient(..) }
.b { background: #myGradient(..) }
.c { background: #myGradient(..) }
Linear gradients (linear-gradient(to bottom, red, blue)) and Radial gradients (radial-gradient(circle, red, blue)) kind of have the same syntax. So I would have four variables like gradientType, gradientOpts, gradientStart, gradientStop and change the gradient type based on the variable. This is just a simplified example.

Answer 1

To answer your question directly, you can use variable interpolation to achieve this.
#myGradient: radial-gradient;
.a { background: ~"#{myGradient}(to bottom, red, blue)"; }
.b { background: ~"#{myGradient}(to bottom, green, yellow)"; }
.c { background: ~"#{myGradient}(to bottom, orange, gold)"; }
But I would suggest using something like a parameterized mixin to handle things like this. Below is the code for a sample mixin which creates either a radial-gradient or linear-gradient depending on the input variable.
#gradType: linear-gradient;
.a { .background(#gradType; to bottom; red; blue); }
.b { .background(#gradType; to bottom; green; yellow); }
.c { .background(#gradType; to bottom; orange; gold); }
.background(#gradType; #gradOpts; #gradStart; #gradEnd){
& when (#gradType = linear-gradient){
background: linear-gradient(#gradOpts, #gradStart, #gradEnd);
}
& when (#gradType = radial-gradient){
background: radial-gradient(#gradOpts, #gradStart, #gradEnd);
}
}
The catch with using guarded mixins (like the above) is that when the #gradType variable has a value outside of the two possible ones (say conical-gradient was the value) then the code would just fail and will not cause any errors to be thrown. This would be a problem when you're writing a library that is going to be used by others (and so want to throw an error when the value is invalid). In such cases, you could change the code like given below. When this approach is used, Less compiler would throw an error when an invalid input value is provided for the #gradType variable.
#gradType: linear-gradient;
.a { .background(#gradType; to bottom; red; blue); }
.b { .background(#gradType; to bottom; green; yellow); }
.c { .background(#gradType; to bottom; orange; gold); }
.background(linear-gradient; #gradOpts; #gradStart; #gradEnd){
background: linear-gradient(#gradOpts, #gradStart, #gradEnd);
}
.background(radial-gradient; #gradOpts; #gradStart; #gradEnd){
background: radial-gradient(#gradOpts, #gradStart, #gradEnd);
}