React And Redux Architecture Issues

Before reading: This isnt a matter of non working code but a question on architecture. Also i am not currently using the ReactRedux library as im first trying to understand how the

Solution 1:

When dealing with redux architecture it can be extremely useful to keep serialisation and immutability at the forefront of every decision, this can be difficult at first especially when you are very used to OOP

As the store's state is just a JS object it can be tempting to use it to keep track of JS instances of more complex model classes, but instead should be treated more like a DB, where you can serialise a representation of your model to and from it in an immutable manner.

Storing the data representations of your bottles in its most primitive form makes things like persistance to localStorage and rehydration of the store possible for more advanced applications that can then allow server side rendering and maybe offline use, but more importantly it makes it much more predictable and obvious what is happening and changing in your application.

Most redux apps i've seen (mine included) go down the functional route of doing away with model classes altogether and simply performing operations in the reducers directly upon the data - potentially using helpers along the way. A downside to this is that it makes for large complex reducers that lack some context.

However there is a middle ground that is perfectly reasonable if you prefer to have such helpers encapsulated into a Bottle class, but you need to think in terms of a case class, which can be created from and serialised back to the data form, and acts immutably if operated upon

Lets look at how this might work for your Bottle (typescript annotated to help show whats happening)

Bottle case class

interface IBottle {
  name: string,
  filledLitres: number
  capacity: number
}

classBottle implements IBottle {

  // deserialisablestaticfromJSON(json: IBottle): Bottle {
    returnnewBottle(json.name, json.filledLitres, json.capacity)
  }

  constructor(public readonly name: string, 
              public readonly filledLitres: number, 
              public readonly capacity: number) {}

  // can still encapuslate computed properties so that is not needed to be done done manually in the viewsgetnameAndSize() {
    return`${this.name}: ${this.capacity} Litres` 
  }

  // note that operations are immutable, they return a new instance with the new statefill(litres: number): Bottle {
    returnnewBottle(this.name, Math.min(this.filledLitres + litres, this.capacity), this.capacity)
  }

  drink(litres: number): Bottle {
    returnnewBottle(this.name, Math.max(this.filledLitres - litres, 0), this.capacity)
  }

  // serialisabletoJSON(): IBottle {
    return {
      name: this.name,
      filledLitres: this.filledLitres,
      capacity: this.capacity
    }
  }

  // instances can be considered equal if properties are the same, as all are immutableequals(bottle: Bottle): boolean {
    return bottle.name === this.name &&
           bottle.filledLitres === this.filledLitres && 
           bottle.capacity === this.capacity
  }

  // cloning is easy as it is immutablecopy(): Bottle {
    returnnewBottle(this.name, this.filledLitres, this.capacity)
  }

}

Store state Notice it contains an array of the data representation rather than the class instance

interface IBottleStore {
  bottles: Array<IBottle>
}

Bottles selector Here we use a selector to extract data from the store and perform transformation into class instances that you can pass to your React component as a prop. If using a lib like reselect this result will be memoized, so your instance references will remain the same until their underlying data in the store has changed. This is important for optimising React using PureComponent, which only compares props by reference.

const bottlesSelector = (state: IBottleStore): Array<Bottle> => state.bottles.map(v =>Bottle.fromJSON(v))

Bottles reducer In your reducers you can use the Bottle class as a helper to perform operations, rather than doing everything right here in the reducer directly on the data itself

interface IDrinkAction {
  type: 'drink'name: string
  litres: number
}

const bottlesReducer = (state: Array<IBottle>, action: IDrinkAction): Array<IBottle> => {
  switch(action.type) {
    case'drink': 
      // immutably create an array of class instances from current statereturn state.map(v =>Bottle.fromJSON(v)) 
              // find the correct bottle and drink from it (drink returns a new instance of Bottle so is immutable)
              .map((b: Bottle): Bottle => b.name === action.name ? b.drink(action.litres) : b)
                // serialise back to date form to put back in the store
                .map((b: Bottle): IBottle => b.toJSON())
    default:
      return state
  }
}

While this drink/fill example is fairly simplistic, and could be just as easily done in as many lines directly on the data in the reducer, it illustrate's that using case class's to represent the data in more real world terms can still be done, and can make it easier to understand and keep code more organised than having a giant reducer and manually computing properties in views, and as a bonus the Bottle class is also easily testable.

By acting immutably throughout, if designed correctly your React class's previous state will continue to hold a reference to your previous bottles (in their own previous state), so there is no need to somehow track that yourself for doing animations etc

Solution 2:

If Bottle class is a react component (or inside a react component) I think you could play with componentWillUpdate(nextProps, nextState) so you can check the previous state (do not unmount your component of course). https://reactjs.org/docs/react-component.html#componentwillupdate

Deep cloning your class doesn't seem a good idea to me.

Edit: "I've also got a React component that displays all Bottle items." That's where you should keep and look for your previous state. Keep all your bottle in a bottles store. And get it in your components when you need to display bottles.

Inside componentWillUpdate you can check you this.state (which is your state just before being updated, ie your previous state) and nextState passed as a parameter which is the current state

Edit2:

why would you keep an complete class in your state ? Just keep data in state. I mean just keep an object that will be updated by your reducer. If you need to have some utils functions (parser...) do not keep them in your state, treat your data in reducers before updating your state or keep your utils/parser functions in some utils file

Also your state should stay immutable. So it means you reducer should return a copy of the updated state anyway.

Solution 3:

I've got an array of Bottle models.

I think It makes more sense to have a model of BottleCollection.

Or maybe you have one Bottle model and multiple usages of it?

classBottle{
    //members
    filledLiters
    filledLitersCapacity
    otherMember1
    otherMember2

    //functionstoPostableObject(){}
}

Hm, it looks like your model represents multiple things:

• a cache of persistent data (retrieved via AJAX?)
• data object (dumb fields)
• a temporary state for user input (data to be POSTed?)

I wouldn't call it a model. It's 3 things: API wrapper/cache, data and pending changes.

I would call it REST API wrapper, data object and application state.

There are complex operations i need to perform on some of the Bottle items using a helper class like so:

var updated_bottles = 
    BottleHandler.performOperationsOnBottles(bottleIds)

It looks to be the domain logic. I wouldn't place the core logic of the application under the name "helper class". I would call it "the model" or "business rules".

    mainStore.dispatch({type:"UPDATED_BOTTLES", updated_bottles:updated_bottles})

That looks to be a change in application state. But I don't see the reason for it. I.e. who requested this change and why?

I dont want to update the store for every operation as i would like the store to be updated all together at the end in one go.

That's a good reasoning.

So you'll have a single action type:

mainStore.dispatch({type:"UPDATED_DATA", { updated_bottles })

However, in this case you might need to clean up old state like this:

mainStore.dispatch({type:"UPDATED_DATA", { updated_bottles: null })

The reason i need to keep "deep clones" of the class instances is so that i can keep the previous state of bottles

I think the reason is that you keep REST API cache and pending changes in a single object. If you keep cache and pending changes in separate objects you don't need clones.

Another thing to note is that your state should be a plain JavaScript object, not an instance of a class. There's no reason to keep references to functions (instance methods) in a state if you know which type of data your state contains. You can just use temporary class instances:

const newBottlesState = newBottleCollection(state.bottlesCache, state.bottlesUserChanges).performOperationsOnBottles()