react-parm

Handle react classes with more functional purity

Table of contents

• Summary
• Usage
• Methods
  • createMethod
  • createValue
  • createRender
  • createComponent
  • createComponentRef
  • createElementRef
  • createCombinedRef
  • createPropType
• Why parm?
• Development

Summary

react-parm is a thin abstraction providing partial-application methods that allow you to handle react classes with much more functional purity. This allows for better encapsulation, greater separation of concerns, and simplified testing. When combined with destructuring, it also improves readability and comprehension.

Usage

import React from "react";
import { createElementRef, createMethod } from "react-parm";
 
export const componentDidMount = ({ getFoo, props }) =>
  props.shouldGetFoo && getFoo();
 
export const onClickGetBar = ({ getBar }, [event]) =>
  getBar(event.currentTarget.dataset.baz);
 
export default class App extends React.Component {
  // lifecycle methods
  componentDidMount = createMethod(this, componentDidMount);
 
  // refs
  element = null;
 
  // instance methods
  onClickGetBar = createMethod(this, onClickGetBar);
 
  render() {
    return (
      <button
        data-baz="quz"
        onClick={this.onClickGetBar}
        ref={createElementRef(this, "element")}
      >
        Go get bar!
      </button>
    );
  }
}

Methods

createMethod

Create a functional instance or lifecycle method, which will receive the full instance as the first parameter.

createMethod(instance: ReactComponent, method: function, ...extraArgs: Array): (instance: ReactComponent, args: Array, extraArgs: Array) => any

import React from "react";
import { createMethod } from "react-parm";
 
export const componentDidMount = ({ setState }) =>
  setState(() => ({ isMounted: true }));
 
export const onClickDoThing = ({ props }, [event], [withStuff]) =>
  props.doThing(event.currentTarget, withStuff);
 
export default class App extends Component {
  state = {
    isMounted: false
  };
 
  componentDidMount = createMethod(this, componentDidMount);
  onClickDoThing = createMethod(this, onClickDoThing, true);
 
  render() {
    return (
      <div>
        <h3>Welcome to doing the thing</h3>
 
        <button onClick={this.onClickDoThing}>Do the thing</button>
      </div>
    );
  }
}

If you want this method to be memoized in an instance-specific way, you can assign the function that will memoize the method to the memoizer property on the function you create the method from.

import memoize from "micro-memoize";
 
const setCount = ({ setState }, [count]) => setState({ count });
 
setCount.memoizer = memoize;

This will automatically wrap the method you pass to createMethod in the memoizer.

createValue

Create a value to assign to the instance based on a functional method which will receive the full instance as the first parameter.

createValue(instance: ReactComponent, method: function, ...extraArgs: Array): any

import React from "react";
import { createValue } from "react-parm";
 
export const getLength = ({ props }) => {
  return props.foo.length;
};
 
export default class App extends Component {
  length = createValue(this, getLength);
 
  render() {
    return <div>The length of the foo parameter is {this.length}</div>;
  }
}

createRender

Create a functional render method, which will receive the props as the first parameter, the full instance as the second parameter, and any arguments passed to it as the third parameter.

createRender(instance: ReactComponent, render: function): (props: Object, instance: ReactComponent, args: Array) => ReactElement

import React from "react";
import { createMethod, createRender } from "react-parm";
 
export const componentDidMount = ({ setState }) =>
  setState(() => ({ isMounted: true }));
 
export const DoTheThing = ({ doThing }, { state: { isMounted } }) => {
  return (
    <div>
      <h3>Welcome to doing the mounted thing</h3>
 
      <span>Am I mounted? {isMounted ? "YES!" : "No :("}</span>
 
      <button onClick={doThing}>Do the thing</button>
    </div>
  );
};
 
export default class App extends Component {
  state = {
    isMounted: false
  };
 
  componentDidMount = createMethod(this, componentDidMount);
 
  render = createRender(this, DoTheThing);
}

NOTE: The difference in signature from createMethod is both for common-use purposes, but also because it allows linting tools to appropriately lint for PropTypes.

createRenderProps

Create a functional render props method, which will receive the props passed to it as the first parameter, the full instance as the second parameter, and any additional arguments passed to it as the third parameter.

createRenderProps(instance: ReactComponent, render: function): (props: Object, instance: ReactComponent, remainingArgs: Array) => ReactElement

import React from "react";
import { createMethod, createRenderProps } from "react-parm";
 
const RenderPropComponent = ({ children }) => (
  <div>{children({ stuff: "passed" })}</div>
);
 
const renderProps = (props, instance) => (
  <div>
    {props.stuff}
 
    <button onClick={instance.props.doThing}>Do the thing</button>
  </div>
);
 
export const DoTheThing = ({ doThing }) => (
  <RenderPropComponent>{renderProps}</RenderPropComponent>
);
 
export default class App extends Component {
  state = {
    isMounted: false
  };
 
  renderProps = createRenderProps(this, renderProps);
 
  render = createRender(this, DoTheThing);
}

NOTE: The main difference between createRender and createRenderProps is the first props argument. In the case of createRender, it is the props of the instance the method is bound to, whereas in the case of createRenderProps it is the props argument passed to it directly.

createComponent

Create a functional component with all available instance-based methods, values, and refs a Component class has.

createComponent(render: function, options: Object): ReactComponent

import React from "react";
import { createComponent } from "react-parm";
 
export const state = {
  isMounted: false
};
 
export const componentDidMount = ({ setState }) =>
  setState(() => ({ isMounted: true }));
 
export const onClickDoThing = ({ props }, [event]) =>
  props.doThing(event.currentTarget);
 
export const DoTheThing = ({ doThing }, { onClickDoThing }) => (
  <div>
    <h3>Welcome to doing the thing</h3>
 
    <button onClick={doThing && onClickDoThing}>Do the thing</button>
  </div>
);
 
DoTheThing.displayName = "DoTheThing";
 
DoTheThing.propTypes = {
  doThing: PropTypes.func.isRequired
};
 
export default createComponent(DoTheThing, {
  componentDidMount,
  onClickDoThing,
  state
});

NOTE: Starting in version 2.6.0, the options can be applied via currying:

export default createComponent({ componentDidMount, onClickDoThing, state })(
  DoTheThing
);

The component will be parmed with createRender, and the properties passed in options will be handled as follows:

• Lifecycle methods will be parmed with createMethod

• Instance methods will be parmed with createMethod, unless:

  • It has a static property of isRender set to true, in which case it will be parmed with createRender. Example:

    const renderer = ({ foo }) => <div>{foo}</div>;
     
    renderer.isRender = true;

  • It has a static property of isRenderProps set to true, in which case it will be parmed with createRenderProps. Example:

    const renderProps = ({ children }) => <div>{children({child: 'props')}</div>;
     
    renderProps.isRenderProps = true;

• Instance values will be assigned to the instance

There are also some additional properties that are treated outside the context of assignment to the instance:

• getInitialState => if a method is passed, then it is parmed and used to derive the initial state instead of the static state property
• getInitialValues => If a method is passed, then it is parmed and used to derive initial instance values
  • Expects an object to be returned, where a return of {foo: 'bar'} will result in instance.foo being "bar"
• isPure => should PureComponent be used to construct the underlying component class instead of Component (defaults to false)
• onConstruct => If a method is passed, then it is called with the instance as parameter at the end of construction

NOTE: Any additional static values / methods you apply to the render component will be re-assigned to the parmed component.

createComponentRef

Create a method that will assign the Component requested to an instance value using a ref callback.

createComponentRef(instance: ReactComponent, ref: string): (component: HTMLElement | ReactComponent) => void

import React from "react";
import { createElementRef } from "react-parm";
 
export default class App extends Component {
  component = null;
 
  render() {
    return (
      <SomeOtherComponent ref={createComponentRef(this, "component")}>
        We captured the component instance!
      </SomeOtherComponent>
    );
  }
}

The ref string value passed will be the key that will be used in the assignment to the instance.

createElementRef

Create a method that will assign the DOM node of the component requested to an instance value using a ref callback.

createElementRef(instance: ReactComponent, ref: string): (component: HTMLElement | ReactComponent) => void

import React from "react";
import { createElementRef } from "react-parm";
 
export default class App extends Component {
  element = null;
 
  render() {
    return (
      <SomeOtherComponent ref={createElementRef(this, "element")}>
        We found the DOM node!
      </SomeOtherComponent>
    );
  }
}

The ref string value passed will be the key that will be used in the assignment to the instance.

createCombinedRef

Create a method that will assign both the DOM node of the component requested and the component itself to a namespaced instance value using a ref callback.

createCombinedRef(instance: ReactComponent, ref: string): (component: HTMLElement | ReactComponent) => void

import React from "react";
import { createCombinedRef } from "react-parm";
 
export default class App extends Component {
  someOtherComponent = null;
 
  render() {
    return (
      <SomeOtherComponent ref={createCombinedRef(this, "someOtherComponent")}>
        I have the best of both worlds! this.someOtherComponent will look like "{component: SomeOtherComponent, element: div}".
      </SomeOtherComponent>
    );
  }
}

The value assigned will be an object with component and element properties, which reflect the component and the DOM node for that component respectively. The ref string value passed will be the key that will be used in the assignment to the instance.

createPropType

Create a custom PropTypes validation method.

createPropType(validator: function): (metadata: Object) => (Error|null)

import { createPropType } from "react-parm";
 
export const isFoo = createPropType(({ component, name, value }) =>
  value === "foo"
    ? null
    : new Error(
        `The prop "${name}" is "${value}" in ${component}, when it should be "foo"!`
      );
);

The full shape of the metadata object passed to createPropType:

{
  component: string, // the name of the component
  key: string, // the key that is being validated
  name: string, // the name of the prop being validated
  path: string, // the full path (if nested) of the key being validated
  props: any, // the props object
  value: any // the value of the prop passed
}

Please note that usage may result in different values for these keys, based on whether the custom prop type is used in arrayOf / objectOf or not.

When used in arrayOf or objectOf:

• key represents the nested key being validated
• name represents the name of the prop that was passed
• path represents the full path being validated

Example:

const isArrayOfFoo = createPropType(
  ({ component, key, name, path, value }) => {
    value === "foo"
      ? null
      : new Error(
          `The key "${key}" for prop "${name}" at path ${path} is "${value}" in ${component}, when it should be "foo"!`
        );
  }
);
...
<SomeComponent bar={['baz']}>
// The key "0" for prop "bar" at path "bar[0]" is "baz" in "SomeComponent", when it should be "foo"!

When the prop type is used in any context other than arrayOf / objectOf, then key, name, and path will all be the same value.

Why parm?

PARM is an acronym, standing for Partial-Application React Method. Also, why not parm? It's delicious.

Development

Standard stuff, clone the repo and npm install dependencies. The npm scripts available:

• build => run rollup to build development and production dist files
• dev => run webpack dev server to run example app / playground
• lint => run ESLint against all files in the src folder
• lint: fix => runs lint with --fix
• prepublish => runs prepublish:compile when publishing
• prepublish:compile => run lint, test:coverage, transpile:lib, transpile:es, and build
• test => run AVA test functions with NODE_ENV=test
• test:coverage => run test but with nyc for coverage checker
• test:watch => run test, but with persistent watcher
• transpile:lib => run babel against all files in src to create files in lib
• transpile:es => run babel against all files in src to create files in es, preserving ES2015 modules (for pkg.module)