create-mutable-context

    0.9.2 • Public • Published

    really minimal wrap on new React.createContext() to provide context with a set function for Consumer

    NOTE

    According to 0002-new-version-of-context, mutation is discouraged. But in some situations, Consumer really need a way to update the Provider. So, I come up with this module.

    Usage

    import createMutableContext from 'create-mutable-context'
     
    const { Provider, Consumer } = createMutableContext()
     
    <Provider defaultValue={1}>
      <Consumer>
        {ctx => {
          // ctx contain value and a set function
          return (
            <button onClick={() => ctx.set(ctx.value + 1)}>
              {ctx.value}
            </button>
          )
        }}
      </Consumer>
    </Provider>

    ctx.set()

    set(updater[, callback])

    set function interface is similar to react component's setState(), which accept updater as object or function.

    updater as function with the signature:

    (prevValue, providerProps) => newValue

    set will just replace the value. It will NOT merge newValue to prevValue.

    keep value in your own state by Provider.onChange

    you can also keep value in your own state (like Input)

    import createMutableContext from 'create-mutable-context'
     
    const { Provider, Consumer } = createMutableContext()
     
    class App extends React.Component {
      state = { valueA: 1 }
      render() {
        return (
          <Provider
            value={this.state.valueA}
            onChange={valueA => this.setState({ valueA })}
          >
          ...
          </Provider>
        )
      }
    }

    access via ctx.foo instead ctx.value.foo

    Can use createStateMutext to mutate whole provider state instead of a value field only.

    import { createStateMutext } from 'create-mutable-context'
     
    const C = createStateMutext({ foo: 1 })
     
    const App = () => (
      <C.Provider>
        <C.Consumer>
          {ctx => (
            <button
              onClick={() => ctx.set({ foo: ctx.foo + 1 })}
            >
              {ctx.foo}
            </button>
          )}
        </C.Consumer>
      </C.Provider>
    )

    createObservableMutext

    Consumers can observe part of changes easily by names. Names are auto calculate to bitmask

    import { createObservableMutext } from 'create-mutable-context'
     
    const C = createObservableMutext({ foo: 0, bar: 0 }, { foo: {}, bar: {} })
     
    const App = () => (
      <C.Provider>
        <C.Consumer
          // observe to foo and only render if foo is changed
          observe="foo"
        >
          {ctx => `Foo: ${ctx.foo}`}
        </C.Consumer>
        <C.Consumer
          // observe to bar and only render if bar is changed
          observe="bar"
        >
          {ctx => `Bar: ${ctx.bar}`}
        </C.Consumer>
        <C.Consumer
          // observe to bar OR foo and render if bar OR foo are changed
          observe="bar,foo"
        >
          {ctx => `BarOrFoo: ${ctx.bar} ${ctx.foo}`}
        </C.Consumer>
      </C.Provider>
    )

    use option to add functions to ctx

    createMutableContext signature:

    import createMutableContext from 'create-mutable-context'
     
    const options = {
      // init at the end of provider constructor
      providerConstruct: (provider) => {},
     
      // init at the end of consumer constructor
      consumerConstruct: (consumer) => {},
     
      // prepare ctx to pass to consumer children function
      consumerCtx: (ctx, consumer) => ctx,
    }
    createMutableContext(defaultValue, calculateChangedBits, option)
     
    const C = createMutableContext(defaultValue, null, {
      providerConstruct(provider) {
        Object.assign(provider.state, {
          inc1() {
            this.set(prevState => { value: prevState.value + 1 })
          }
        })
      },  
    })
     
    const App = () => (
      <C.Provider>
        <C.Consumer>
          {ctx => (
            <button
              // can call inc1
              onClick={ctx.inc1}
            >
              {ctx.value}
            </button>
          )}
        </C.Consumer>
      </C.Provider>
    )

    Install

    npm i create-mutable-context

    DownloadsWeekly Downloads

    0

    Version

    0.9.2

    License

    MIT

    Unpacked Size

    39.8 kB

    Total Files

    12

    Last publish

    Collaborators

    • ericfong