Renuka Patil

Posted on Nov 13

NGRX with Angular 16

#angular #ngrx #typescript

Component dispatches action to indicate something is happened.
Reducers → How actions modify state are the reducers, so, they detected all of the actions being dispatched in the app and determine how state should be modified. We have reducers for each feature or entity in the app like todo’s, auth, articles and so...

Reducers are pure functions, take some input and they always will produce same output of same type.
Reducers detect action, take current state and store new state in the store.
Store which is often global is where all of the state for your application lives, it is one big object full of data and when a component wants to use some of that state from store(like currently todo’s) it can use Selector to pull in the state that it needs from the store, now that is almost whole story.

3.Effects -> Up to now, we can’t make asynchronous calls to go load in data from a server, this model works well enough, we are dispatching actions like add todo or remove todo because we immediately send the data we need along with that action.
But if we want to load data into an application and add it to the store, we might do this with an async operation that’s going to call a service, that’s going to load in some data from API somewhere and that’s going to take some time to complete, so this is where effects come into play like reducer. An effect can also listen to all of the actions being dispatched in the app but unlike a reducer that has to be a pure function intended just to update the state an effect can run whatever side effects it like in the case of loading data we would first dispatch an action like load todo this will be immediately handled by the reducers but we don’t have data we need yet because we need make a call to the service to load the data so all the reducers will do in response to that load to do’s action is do some like set a flag in the store changing status to do state to loading or something like that.

However our effects will also listen for that load todo action and where it detects this, it will go off and fetch the todo from the service and once data has finished loading it will dispatch a new action either load todo success or failure.

now reducer can handle this load to do a successful action that was just dispatched from effect and this action will already have all of the data available to it so the reducer can set that status flag to success and it can update the todo’s property in the store with the data as we just loaded.

Let's dig into this with actually working on the project:

Clone this project from github and you will have directory like this:

run these commands in terminal:
ng install or yarn install

run the project with command
ng start

After running the project you will see output like this:

Let's see steps wise implementation of the project:

Show all the list of grocery on webpage - using Reducer
Add action and dispatched from increment button in grocery component - using action, reducer and selector.
Show the added grocery item in bucket component - using selector
Add action for remove the item from grocery component and remove from bucket component - using action, reducer and selector
Filter the list of grocery component by type selected - using Selector
Fetch the grocery list from API - using Effects

1. Show all the list of grocery on webpage - using Reducer

Add store folder
In store folder add reducers folder
Add file grocery.reducer.ts and add below code


import { createReducer, on } from "@ngrx/store"
import { Grocery } from "src/models/grocery.model"

const initialState:Grocery[] = [
    { "id": 1, "name": "Milk", "type": "fruit" },
    { "id": 2, "name": "Banana", "type": "fruit" },
    { "id": 3, "name": "lays chips", "type": "snacks" },
    { "id": 4, "name": "doritos", "type": "snacks" }
]

export const groceryReducer = createReducer(initialState);

Go to app.module.ts and add above reducer here

@NgModule({
  declarations: [
      //...existing components
  ],
  imports: [
    //...existing properties

    **StoreModule.forRoot({groceries: groceryReducer}),**

      //...existing properties
    })

  ],
  providers: [ ],
  bootstrap: [AppComponent]
})
export class AppModule { }

Now, go to the http://localhost:4200/ and inspect the page and open redux devtool
You will see he initialState of groceries object present under state in redux devtool

2. Add actions and dispatched them from incrementand decrement button in grocery component - using action, reducer and selector.

Dispatching action -> You have dispatched action from increment button in grocery.component.ts file. so, whenever you push increment button on UI, you will see action displayed in redux devtool.

You will see in redux devtool under action tab there is action dispatched.

Better synax of creating action -Add actions folder in store folder -Add file bucket.action.ts -Add below code there

import { createAction} from "@ngrx/store";
import { Bucket } from "src/models/bucket.model";


export const addToBucket = createAction(
    '[Bucket] Add to Bucket',
    props<{ payload: Bucket }>()
  );

and this is how you can dispatch action in grocery.component.ts

now you will see type and payload dipatched here

Bind Dispatched action with reducer and update the state.

Action will dispatched from grocery component → bucket.reducer → we will modify the state

i)Create another file bucket.reducer.ts in store/reducers folder.
Here it takes action and we telling what to do with data- so this addToBucket has access of 2 things - state and action - so in state we are sending the state as it is and new payload as action which we are dipatching the action from component.

import { createReducer, on } from "@ngrx/store";
import { Bucket } from "src/models/bucket.model";
import { addToBucket, removeFromBucket } from "../actions/bucket.action";


const initialState: Bucket[] = [];

export const bucketReducer = createReducer(initialState,
    on(addToBucket, (state, action) => {

            return [
                ...state,
                action.payload
            ]

    }),
);

Now you can see in redux devtool, when we are pushing increment button it dispatch the action with payload which we are collecting in reducer and adding new state.

What if we are adding same item multiple times then only quantity will increment.

import { createReducer, on } from "@ngrx/store";
import { Bucket } from "src/models/bucket.model";
import { addToBucket, removeFromBucket } from "../actions/bucket.action";


const initialState: Bucket[] = [];

export const bucketReducer = createReducer(initialState,
    on(addToBucket, (state, action) => {
        const bucketItem = state.find(item => item.id === action.payload.id);
        if (bucketItem) {
            return state.map(item => {
                return item.id === action.payload.id ? { ...item, quantity: item.quantity + action.payload.quantity } : item
        });
        }else{
            return [
                ...state,
                action.payload
            ]
        }
    }),
);

Now you will see the item is added multiple times

Remove bucket item from reducer state Create action remove from bucket

Dispatched from decrement button in grocery.component.ts file

Listen this dispatched action in bucket reducer.

import { createReducer, on } from "@ngrx/store";
import { Bucket } from "src/models/bucket.model";
import { addToBucket, removeFromBucket } from "../actions/bucket.action";


const initialState: Bucket[] = [];

export const bucketReducer = createReducer(initialState,
    on(addToBucket, (state, action) => {
        const bucketItem = state.find(item => item.id === action.payload.id);
        if (bucketItem) {
            return state.map(item => {
                return item.id === action.payload.id ? { ...item, quantity: item.quantity + action.payload.quantity } : item
        });
        }else{
            return [
                ...state,
                action.payload
            ]
        }
    }),

    on(removeFromBucket, (state, action) => {
        const bucketItem = state.find(item => item.id === action.payload.id);
        if (bucketItem && bucketItem.quantity > 1) {
            return state.map(item => {
                return item.id === action.payload.id ? { ...item, quantity: item.quantity - 1 } : item
            });
        }else{
            return state.filter(item => item.id !== action.payload.id);
        }


    })
);

Now, you see after decrement button pushed the quantity of item will reduced by 1.

3.Show the added grocery item in bucket component - using selector
We are selecting the state in bucket.component.ts file

And displaying in bucket.component.html file

And this is how it looks - added milk 2 times - so the action is dispatched and selected in bucket component.

4.Filter the list of grocery component by type selected - using Selector
Selectors - transform data before selecting and showing data

Create selectorsfolder under the store folder and add file grocery.selectors.ts.

Use in grocery.component.ts file like this

Another way to create selector

5.Add Selector which select only type of grocery

Create selector selectGroceryByType

Use in grocery.component.ts file like this

this is how it select only fruit type

6. Select with dropdown
Make changes in component so that it can show item for selected type in grocery.component.ts file

modify the selector for choosing type only

and modify grocery.component.html file

Now, when you select from dropdown you will see the items for selected type only.

Fetch the grocery list from API - using Effects
Until now we have action as synchronous - To make this action Async
to perform side effects such as calling API and fetching data

We have db.json file where there is list of the items, now we will use that and will fetch the items from here using effects.
Add this line in package.json file

now run the command npm run apiServer in terminal, so that our db.json file will run. 1)now we will call data from api for that we will keep initialState as null