macro-components

Create flexible layout and composite UI components without the need to define arbitrary custom props.

npm i macro-components

import React from 'react'
import styled from 'styled-components'
import macro from 'macro-components'
import { space, fontSize, color } from 'styled-system'

// Define some styled-components
const Box = styled.div`${space} ${fontSize} ${color}`

// Ensure components have a `displayName`
Box.displayName = 'Box'

const Heading = styled.h2`${space} ${fontSize} ${color}`
Heading.displayName = 'Heading'

const Text = styled.div`${space} ${fontSize} ${color}`
Text.displayName = 'Text'

// Create a macro-component
const MediaObject = macro(({
  Image,
  Heading,
  Text
}) => (
  <Flex p={2} align='center'>
    <Box width={128}>
      {Image}
    </Box>
    <Box>
      {Heading}
      {Text}
    </Box>
  </Flex>
))

// Use the macro-component by passing the components as children
const App = props => (
  <div>
    <MediaObject>
      <Image src='kitten.png' />
      <Heading>
        Hello
      </Heading>
      <Text>
        This component keeps its tree structure but still allows for regular composition.
      </Text>
    </MediaObject>
  </div>
)

Features

• Single component creator
• Intended for use with libraries like styled-components & glamorous
• Encapsulate layout structure in composable components
• Help keep your component API surface area to a minimum
• Works with any other React components

Motivation

Often it's best to use React composition and props.children to create UI that is composed of multiple elements, but sometimes you might want to create larger composite components with encapsulated tree structures for layout or create Bootstrap-like UI components such as panels, cards, or alerts. This library lets you create composite components with encapsulated DOM structures without the need to define arbitrary props APIs and that work just like any other React composition.

This can help ensure that your component API surface area remains small and easier to maintain.

If you find yourself creating composite React components that don't map to data structures, as described in Thinking in React, then this module is intended for you.

Usage

macro(elementFunction)

Returns a React component with a composable API that keeps tree layout structure.

const Banner = macro(({
  Heading,
  Subhead
}) => (
  <Box p={3} color='white' bg='blue'>
    {Heading}
    {Subhead}
  </Box>
)

By default, the elementFunction argument is called with an object of elements based on the element type or component displayName. Using the Banner component above would look something like the following.

<Banner>
  <Heading>Hello</Heading>
  <Subhead>Subhead</Subhead>
</Banner>

To ensure correct placement or for when there are multiples of the same child component type, use the name prop to specify which child element is inserted in a particular location in the tree.

<Banner>
  <Heading>Hello</Heading>
  <Heading name='Subhead'>Subhead</Heading>
</Banner>

elementFunction

The element function is similar to a React component, but receives an elements object as its first argument and props as its second one. The elements object is created from its children and is intended to make encapsulating composition and element structures easier.

Within the macro component, the element function is called with the elements object and props: elementFunction(elementsObject, props).

// example
const elFunc = ({ Heading, Text, }, props) => (
  <header>
    {Heading}
    {Text}
  </header>
)

const SectionHeader = macro(elFunc)

Omitting children

For any element not passed as a child to the macro component, the element function will render undefined and React will not render that element. This is useful for conditionally omitting optional children

const Message = macro({
  Icon,
  Text,
  CloseButton
}) => (
  <Flex p={2} bg='lightYellow'>
    {Icon}
    {Text}
    <Box mx='auto' />
    {CloseButton}
  </Flex>
)

// Omitting the Icon child element will render Message without an icon.
<Message>
  <Text>{props.message}</Text>
  <CloseButton
    onClick={props.dismissMessage}
  />
</Message>

Props passed to the root component

The second argument passed to the element function allows you to pass props to the root element or any other element within the component.

const Card = macro(({
  Image,
  Text
}, props) => (
  <Box p={2} bg={props.bg}>
    {Image}
    {Text}
  </Box>
))

// example usage
<Card bg='tomato'>
  <Image src='kittens.png' />
  <Text>Meow</Text>
</Card>

Clone Component

To apply default props to the elements passed in as children, use the Clone component in an element function.

import macro, { Clone } from 'macro-components'

const Header = macro(({ Heading, Text }) => (
  <Box p={2}>
    <Clone
      element={Heading}
      fontSize={6}
      mb={2}
    />
    <Clone
      element={Text}
      fontSize={3}
    />
  </Box>
))

Related

• styled-components
• glamorous
• emotion
• styled-system
• system-components
• MediaObject example based on: The media object saves hundreds of lines of code

MIT License