@forminator/react-wire

connect react components with wire

• Motivation
• Install
• Usage
• API
  • useWire hook
  • useWireValue hook
  • useWireState hook
  • get/set wire value
  • fns object and useFn hook
• Advanced API
  • Global wire
  • useSelector hook
  • createSelector function
  • useSubscribe hook
  • Subscribe to the wire
  • useInterceptor hook
• Notes
  • undefined value vs null value
  • Initial value
  • Rewiring

Motivation

• top-level components
  • doesn't care about the value
  • care about the connection between components
• detailed components
  • only care about the value
  • doesn't care about where the value came from or will be used
• controlled/uncontrolled components should be easy to write
• choosing the correct state location shouldn't be too hard

Install

yarn add @forminator/react-wire

Add proxy-polyfill to support ie browser. proxy support is more than 90% in browsers, more detail

Usage

With pure react, you use useState to store state:

function FancyInput(props) {
  const [value, setValue] = useState('');

  return <input value={value} onChange={(e) => setValue(e.target.value)} />;
}

function FancyPage() {
  return <FancyInput />;
}

Let's add a new feature, a filterable list that gets a string as a filter and only shows items containing that string. Now we need to read the state of input outside of the FancyInput component; so we have to move the state to the parent component:

function FancyInput(props) {
-  const [value, setValue] = useState('');
+  const { value, setValue } = props;

  return <input value={value} onChange={(e) => setValue(e.target.value)} />;
}

function FancyList(props) {
  const [filter, setFilter] = useState('');
  return (
    <>
      <FancyInput value={filter} setValue={setFilter} />
      <List items={props.items} filter={filter} />
    </>
  );
}

• you need to refactor all the FancyInput usages, pass value, and setValue to make it work as expected
• the top-level component (FancyList) re-renders each time the filter changes

Let see how react-wire helps you:

Same as above, but use useWireState instead of useState:

function FancyInput(props) {
  const [value, setValue] = useWireState(null, '');

  return <input value={value} onChange={(e) => setValue(e.target.value)} />;
}

Right now FancyInput is uncontrolled. If you need to make it controllable, you should pass an up-link wire.

function FancyInput(props) {
-  const [value, setValue] = useWireState(null, '');
+  const [value, setValue] = useWireState(props.value$, '');

  return <input value={value} onChange={(e) => setValue(e.target.value)} />;
}

And create a wire with the useWire hook and pass it to components:

function FancyList(props) {
  const filter$ = useWire(null, '');
  return (
    <>
      <FancyInput value$={filter$} />
      <List items={props.items} filter$={filter$} />
    </>
  );
}

With this new code:

• all the FancyInput uncontrolled usages are working as expected without any change
• the Top-level component (FancyList) will not re-render each time the value changes
• only detailed components (FancyInput, List) will re-render each time the value changes
• FancyInput is now controllable and can be used as a controlled or uncontrolled component by passing a wire
• FancyList can be controllable if you want:

function FancyList(props) {
  const filter$ = useWire(props.filter$, '');
  /* ... */
}

react-wire has more advanced features:

• selectors to maintain calculated values
• fns to pass function calls over the wire

API

useWire hook

useWire hook creates and returns new wire. in the next renders, returns the same wire.

// without up-link wire and initial value
const wire = useWire<type>(null);

// with initial value
const wire = useWire(null, initialValue);

// with up-link wire
const wire = useWire(anotherWire);

// with up-link and initial value
const wire = useWire(anotherWire, initialValue);

• If up-link wire has value, initial value will be ignored
• If up-link wire has undefined value, initial value will be set on up-link wire

// Lazy initial value
const wire = useWire(anotherWire, () => initialValue);

useWireValue hook

useWireValue hook returns current wire value and subscribes for value updates

const value = useWireValue(wire);

// returns `defaultValue` if the wire is `null` or `undefined` or wire has an `undefined` value
const value = useWireValue(wire, defaultValue);

useWireState hook

useWireState behaves like react useState, and keeps state and wire value in sync

// exactly same as useState
const [state, setState] = useWireState(null, initialValue);

// without initial value
const [state, setState] = useWireState(wire);

// with wire and initial value
const [state, setState] = useWireState(wire, initialValue);

• If the wire has value, the initial value will be ignored and respect wire value
• If the wire has undefined value, the initial value will be used and wire value will be updated

// Lazy initial value
const [state, setState] = useWireState(wire, () => initialValue);

// new value
setState(value);

// functional update
setState((value) => update(value));

note: If current state is undefined, updater function won't be called! you can pass initialValue to useWireState or make sure the wire has value to avoid this behavior.

get/set wire value

// get value
const value = wire.getValue();

// set value
wire.setValue(someValue);

fns object and useFn hook

With fns object and useFn hook, you can transfer function calls over wires. Callback function should be memoized with useCallback

// subscribe for `sample` function call
useFn(
  wire,
  'sample',
  useCallback((value) => {
    console.log(value);
  }, []),
);

// call `sample` function
wire.fns.sample(5);

you can define typing for fns and useFn.

type Value = number;
interface Fns {
  sample: (n: number) => void;
}

const wire = useWire<Value, Fns>(null);

// code
wire.fns.sample();

error:

error TS2554: Expected 1 arguments, but got 0.
wire.fns.sample();
         ~~~~~~~~
    sample: (n: number) => void;
             ~~~~~~~~~
    An argument for 'n' was not provided.

// code
useFn(
  wire,
  'sample',
  useCallback((n: string) => {}, []),
);

error:

error TS2345: Argument of type '(n: string) => void' is not assignable to parameter of type '(n: number) => void'.
  Types of parameters 'n' and 'n' are incompatible.
    Type 'number' is not assignable to type 'string'.

useFn(wire, 'sample', useCallback((n: string) => {}, []));
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

up-link wire should have an exact type for each function, but can have more functions.

interface AB {
  a: (n: number) => void;
  b: (n: string) => void;
}
interface A {
  a: (n: number) => void;
}
interface B {
  b: (n: string) => void;
}
interface C {
  c: (n: string) => void;
}
const wireAB = useWire<Value, AB>(null);
const wireA = useWire<Value, A>(wireAB);
const wireB = useWire<Value, B>(wireAB);
const wireB = useWire<Value, C>(wireAB); // error

Advanced API

Global wire

If you want have a global wire you can createWire function.

const themeWire = createWire<'light' | 'dark'>('light');

function SomeComponent() {
  const theme = useWireValue(themeWire);
}

useSelector hook

useSelector creates and returns a new selector. a selector is a wire with the calculated value.

const wire = useWire(null, 4);
const selector = useSelector({
  get: ({ get }) => get(wire) * 2,
});

selector.getValue(); // 8

You can create a writable selector with passing the set option.

const wire = useWire(null, 4);
const selector = useSelector({
  get: ({ get }) => get(wire) * 2,
  set: ({ set }, value) => set(wire, value / 2),
});

selector.setValue(6);
wire.getValue(); // 3

You can define a dependencies list for dependencies of options.

const { n } = props;
const wire = useWire(null, 4);
const selector = useSelector(
  {
    get: ({ get }) => get(wire) * n,
    set: ({ set }, value) => set(wire, value / n),
  },
  [n],
);

createSelector function

createSelector creates a new selector. It can be used outside of the react.

const themeWire = createWire<'light' | 'dark'>('light');
const textColor = createSelector({
  get: ({ get }) => (get(themeWire) === 'light' ? '#000' : '#fff'),
});

function SomeComponent() {
  const color = useWireValue(textColor);
}

useSubscribe hook

Every time the wire value changes, the callback function would be called

// subscribe
useSubscribe(
  wire,
  useCallback((value) => {
    /* ... */
  }, []),
);

Subscribe to the wire

Every time the wire value changes, the callback function would be called

// subscribe
const unsubscribe = wire.subscribe((value) => {
  /* ... */
});

// unsubscribe
unsubscribe();

useInterceptor hook

in some rare use-cases you need changing wire behavior and interfering set value. useInterceptor helps in these use-cases.

useInterceptor hook gets wire and interceptor function and returns new wire. on every setValue of returned wire, the interceptor function gets next value and previous value and returns a new value. the returned value of the interceptor will be set on the wire.

const wire = useInterceptor(anotherWire, (nextValue, preValue) => /* anotherValue */)

example:

const valueWire = useInterceptor(
  props.valueWire,
  useCallback(
    (nextValue, preValue) =>
      props.submittingWire.getValue() ? preValue : nextValue,
    [props.submittingWire],
  ),
);

Notes

undefined value vs null value

• undefined value means the wire has no value and other wires may set its value during their initialization.
• null value means the wire has value and value is null and other wires don't override its value during their initialization

Initial value

During initialization, wire value always has more priority.

• If the up-link wire has value, the initial value will be ignored and respect wire value
• If the up-link wire has undefined value, the initial value will be used and wire value will be updated

Examples:

const wire1 = useWire(null, 1);
const wire2 = useWire(wire1, 2);

wire1.getValue(); // => 1
wire2.getValue(); // => 1

const wire1 = useWire(null);
const wire2 = useWire(wire1, 2);

wire1.getValue(); // => 2
wire2.getValue(); // => 2

const wire = useWire(null, 1);
const [state] = useWireState(wire, 2);

wire.getValue(); // => 1
state; // => 1

const wire = useWire(null);
const [state] = useWireState(wire, 2);

wire.getValue(); // => 2
state; // => 2

Rewiring

Please avoid changing the wire variable. if wire argument changed, a warning will be shown.

// wrong, avoid.
const wire = useWire(condition ? wire1 : wire2);
const value = useWireValue(condition ? wire1 : wire2);
const [state, setState] = useWireState(condition ? wire1 : wire2);