Unlock the Power of Compound Components
When it comes to building robust and scalable user interfaces, components are an essential tool in every developer’s toolkit. However, as the complexity of our interfaces grows, so does the need for more sophisticated component architectures. This is where compound components come into play.
What are Compound Components?
Compound components are groups of individual components that work together to create a cohesive and complex behavior. They share state behind the scenes, providing an intuitive and expressive syntax for the programmer using the components. A classic example of compound components is the <select> and <option> elements in vanilla HTML, which come together to form a complex input control.
Designing Compound Components
Before diving into implementation, it’s essential to determine whether a compound component is the right fit for your API design. Ask yourself:
- Does the programmer need to compose multiple components to achieve the desired result?
- Are the interactions and roles between components clear and intuitive?
Some common UI paradigms that lend themselves to the compound component pattern include advanced tables, searchable dropdowns, and customizable filters.
Building a Compound Component in React
To implement a compound component in React, we’ll leverage hooks, functional components, and the Context API. Let’s build a rough draft of a compound component that allows users to select multiple options from a list, using a text field to filter the list if desired.
We’ll create two sub-components: EnhancedMultiSelect and EnhancedMultiSelectOption. The former will encapsulate the state of the child options, render the text field for filtering, and provide a context for sharing state between components. The latter will express the individual selectable options, read from and write to the selection state, and exclude itself from rendering if the filter value doesn’t match.
Implementing the Compound Component
First, we’ll create a context to share state between the parent and child components. Then, we’ll implement the signature for our component, which will take three props: children, value, and onChange. We’ll use a useState hook to keep track of the query the user has typed into the filter text input and return the components that React will render.
Next, we’ll implement the EnhancedMultiSelectOption component, which will consume the context provided by the parent component and render a checkbox and any children the consumer of our component would like to render.
Putting it All Together
To see how it all works together, we’ll consume our compound component and render it in an entry point App component. This will give us a working example of our filterable multi-select compound component.
Angular Implementation
We can also implement the same compound component using the Angular framework. We’ll create an outer component with a simple template containing a text input with two-way binding to the filter property, and an inner component that renders a label wrapping the checkbox and the content of the component.
Conclusion
Compound components offer a powerful way to create complex behaviors by combining individual components. By carefully considering the trade-offs and design implications, we can create intuitive and expressive APIs that make it easier for developers to build robust and scalable user interfaces.