How about just intercepting setModel?

[tgoorden]

OK, I was a bit too fast in stating that 2.0.0 fixed my issue. My goal was to intercept setModel, not setProperty and it's still impossible to override. Now that I understand what is happening, it's easy to see why: if you don't override setProperty, it will still be "locked in" with the original setModel function.

This for example will not work.

const middleware = function(props) {
  const { setModel, ...xProps } = props
  const interceptedSetModel = (model)=> {
    console.log("Intercepting model")
    console.log(model)
    return setModel(model)
  }
  return { setModel: interceptedSetModel, ...xProps }
}

const SimpleForm = props => {
  const { bindInput } = props
  return (
    <Form>
      <Input {...bindInput('example')} />
    </Form>
  )
}

const ReformedForm = reformed(middleware)(SimpleForm)

Now, you may begin to wonder why we would want to use that?

Let's say we're creating a dynamic form that has "repeatable" parts. The output we are aiming for is an array like this:

output = [
  {
     name: "foo",
     value: "hello"
  },
  {
     name: "bar",
     value: "world"
  },
]

If I can intercept setModel, I can easily store the state of the entire "form" into an array inside of a higher order state object. We could perhaps do this with setProperty as well, but I'm betting this will break bindInput, etc because the internal state of the "lower order" reformed component will not be updated anymore...

[tgoorden]

OK, since this was making me itch, I've figured out a way that is potentially more elegant.

Essentially, setModel, setProperty and the binding are all hooked into the state somehow. This implies that intercepting one would basically force you to intercept all. Otherwise, there is no way of keeping the (model) state predictable, without terribly complex code.

So, the solution seems to abstract out the model state handling instead. In fact, in all likelihood this is what any middleware is interested in anyway. The rest is solvable on a (form) component level.

I've reworded reformed.js to reflect this approach. The middleware can (in this system) intercept setModel, getModel and/or setModelValue and getModelValue. For instance a validator would be able to work with setModelValue to mark dirty fields, etc.

Incidentally, it seems to me that it would make sense to do all this in the constructor instead of the render function, no?

import React from 'react'
import PropTypes from 'prop-types'
import assign from 'object-assign'
import hoistNonReactStatics from 'hoist-non-react-statics'

const makeWrapper = (middleware) => (WrappedComponent) => {
  class FormWrapper extends React.Component {
    static propTypes = {
      initialModel: PropTypes.object,
    }

    constructor (props, ctx) {
      super(props, ctx)
      this.state = {
        model: props.initialModel || {},
      }
      class ModelHandlerWrapper {
        constructor({getState,setState}) {
          this.getState = getState
          this.setState = setState
        }
        setModel = (model) => { 
          this.setState({model})
          return model
        }
        getModel = ()=> getState("model")
        getModelValue = (name)=> this.getModel()[name]
        setModelValue = (name,value)=> {
          return this.setModel(assign({}, this.getModel(), {
            [name]: value,
          }))
        }
      }
      const getState = (name) => this.state[name]
      this.modelHandler = new ModelHandlerWrapper({getState: getState, setState: this.setState.bind(this)})
      if (typeof middleware === 'function') {
        this.modelHandler = middleware(this.modelHandler)
      }
    }

    setModel = (model) => {
      return this.modelHandler.setModel(model)
    }

    setProperty = (prop, value) => {
      return this.modelHandler.setModelValue(prop,value)
    }

    // This, of course, does not handle all possible inputs. In such cases,
    // you should just use `setProperty` or `setModel`. Or, better yet,
    // extend `reformed` to supply the bindings that match your needs.
    bindToChangeEvent = (e) => {
      const { name, type, value } = e.target

      if (type === 'checkbox') {
        const oldCheckboxValue = this.modelHandler.getModelValue(name) || []
        const newCheckboxValue = e.target.checked
          ? oldCheckboxValue.concat(value)
          : oldCheckboxValue.filter(v => v !== value)

        this.setProperty(name, newCheckboxValue)
      } else {
        this.setProperty(name, value)
      }
    }

    bindInput = (name) => {
      return {
        name,
        value: this.modelHandler.getModelValue(name) || '',
        onChange: this.bindToChangeEvent,
      }
    }

    render () {
      let nextProps = assign({}, this.props, {
        model: this.modelHandler.getModel(),
        setProperty: this.setProperty,
        setModel: this.setModel,
        bindInput: this.bindInput,
        bindToChangeEvent: this.bindToChangeEvent
      })

      return React.createElement(WrappedComponent, nextProps)
    }
  }

  FormWrapper.displayName = `Reformed(${getComponentName(WrappedComponent)})`
  return hoistNonReactStatics(FormWrapper, WrappedComponent)
}

const getComponentName = (component) => (
  component.displayName ||
  component.name
)

export default makeWrapper

[dvdzkwsk]

Yeah, I'd realized the patch wouldn't affect setModel, but didn't think it should be necessary because it's an implementation detail of setProperty; that is, the consumer shouldn't rely on setProperty dispatching to setModel.

I will read through your proposals when I get some time today, but wanted to get a quick response out. Thank you for the detailed post. If it's a clean enough solution we can consider it :).

[dvdzkwsk]

I took a look at your proposal, and it seems pretty solid for your use case. I do have some reservations, though, mainly that the middleware function would only run once, at component instantiation time, which would break the expected function signature of Props -> Props and restrict its overall utility.

At this point I'm wondering if this is something that middleware shouldn't even be responsible for, since the only reliable way to update function references after applying middleware is to have them rely on this, but that presents its own set of problems. For what it's worth, middleware at the top-level wasn't something I'd ever really intended to be a core part of the API, but was added mainly as an easy escape hatch.

I would really like to solve for this though, so I'm continuing to play around with a few ideas on my end. If this is blocking you, though, please feel free to fork this project in the meantime :).

[tgoorden]

Yes, I agree that it's an interesting (architectural) challenge. To be honest I'm not familiar enough with the React lifecycle and it's architectural consequences to make a good estimate here. However, it seems to me that it wouldn't be too hard to use this approach inside of the "render" cycle. I guess you would end up with some kind of generator functionality like you wrote before for the bindInput function, but this time with a "model handler" as its argument instead of setProperty.

The current code is quite tied into this to be able to do this without a significant rewrite so I ended up taking the easy way out, which meant doing it at constructor time.

[tgoorden]

OK, this seems to work fine and it allows the middleware to jump in during the render cycle:

You might note that I'm using set and get from lodash to allow "dotted" property names to be used, with a correct translation into an object structure. This adds a lot of extra functionality IMO.

import React from 'react'
import PropTypes from 'prop-types'
import assign from 'object-assign'
import hoistNonReactStatics from 'hoist-non-react-statics'
import { set, get } from 'lodash'

class ModelHandlerWrapper {
  constructor({getState,setState}) {
    this.getState = getState
    this.setState = setState
  }
  setModel = (model) => { 
    this.setState({model})
    return model
  }
  getModel = ()=> this.getState("model")
  getModelValue = (name)=> get(this.getModel(),name)
  setModelValue = (name,value)=> {
    return this.setModel(set(this.getModel(),name,value))
  }
}

const makeWrapper = (middleware) => (WrappedComponent) => {
  class FormWrapper extends React.Component {
    static propTypes = {
      initialModel: PropTypes.object,
    }

    constructor (props, ctx) {
      super(props, ctx)
      this.state = {
        model: props.initialModel || {},
      }
    }

    makeHelpers = (modelHandler) => {
      bindToChangeEvent = (e) => {
        const { name, type, value } = e.target
        if (type === 'checkbox') {
          const oldCheckboxValue = modelHandler.getModelValue(name) || []
          const newCheckboxValue = e.target.checked
            ? oldCheckboxValue.concat(value)
            : oldCheckboxValue.filter(v => v !== value)

          modelHandler.setModelValue(name, newCheckboxValue)
        } else {
          modelHandler.setModelValue(name, value)
        }
      }
      helpers = {
        setModel: (model) => modelHandler.setModel(model)
        ,
        setProperty: (prop, value) => modelHandler.setModelValue(prop,value)
        ,
        bindToChangeEvent: (e) => {
          const { name, type, value } = e.target

          if (type === 'checkbox') {
            const oldCheckboxValue = modelHandler.getModelValue(name) || []
            const newCheckboxValue = e.target.checked
              ? oldCheckboxValue.concat(value)
              : oldCheckboxValue.filter(v => v !== value)

            modelHandler.setModelValue(name, newCheckboxValue)
          } else {
            modelHandler.setModelValue(name, value)
          }
        }
        ,
        bindInput: (name) => {
          return {
            name,
            value: modelHandler.getModelValue(name) || '',
            onChange: bindToChangeEvent,
          }
        }
      }
      return helpers
    }

    render () {
      const getState = (name) => this.state[name]
      let modelHandler = new ModelHandlerWrapper({getState: getState, setState: this.setState.bind(this)})
      if (typeof middleware === 'function') {
        modelHandler = middleware(modelHandler)
      }
      let nextProps = assign({}, this.props, {
        model: modelHandler.getModel()
      },
        this.makeHelpers(modelHandler)
      )
      return React.createElement(WrappedComponent, nextProps)
    }
  }

  FormWrapper.displayName = `Reformed(${getComponentName(WrappedComponent)})`
  return hoistNonReactStatics(FormWrapper, WrappedComponent)
}

const getComponentName = (component) => (
  component.displayName ||
  component.name
)

export default makeWrapper