Dynamic components

Dynamic components are components that generate styles based on their props. You can derive styles from props, apply a variant conditionally, or any other logic.

styled.{{tag}} can be defined by a function, where it should return a string. This function is going to be available via the props API for that component, including all props from the element. Like following:

module Dynamic = %styled.div( (~color, ~background) => `
  color: $(color);
  background-color: $(background);
`)
 
<Dynamic color=CSS.hex("#EB5757") background=CSS.hex("#516CF0")>
  {React.string("Hello!")}
</Dynamic>

module Dynamic = [%styled.div (~color, ~background) => {|
  color: $(color);
  background-color: $(background);
|}];
 
<Dynamic color={CSS.hex("#EB5757")} background={CSS.hex("#516CF0")}>
  {React.string("Hello!")}
</Dynamic>;

Note: The returned expression (the last expression of the function) needs to be an string (it can’t be a reference or a function call). This is a limitation of ppxes where it needs to check the current AST to know which type it is.

All the rules from Interpolation are applied here. In the example, color and background are CSS.Color.t CSS.Color.t since it gets inferred from the CSS property. It’s called type holes https://twitter.com/davesnx/status/1552305210558742528

Name collision

If you create a dynamic component with a prop with the same name as a makeProp it will collide and styled-ppx will override it (and would replace the prop entirely).

For example, if your dynamic component is defined with a prop “size” it will override size from makeProps.