In this article we will build a fully-functional file upload control, that is powered by Angular and is backed by an NgRx feature store. The control will provide the user with the following features:
- The ability to upload files using the
<input #file type="file" />
HTML element. - The ability to see accurate upload progress via the
reportProgress
HttpClient
option. - The ability to cancel in-process uploads
As an added bonus, we will briefly dive into building the server-side ASP.NET Core WebAPI Controller that will handle the file uploads.
Before We Get Started
In this article, I will show you how to manage file uploads using NgRx. If you are new to NgRx, then I highly recommend that you first read my article, NgRx - Best Practices for Enterprise Angular Applications. We will be using the techniques described in that article to build out the NgRx components for file uploads.
If you are new to Angular, then I recommend that you check out one of the following resources:
NPM Package Versions
For context, this article assumes you are using the following npm
package.json
versions:
-
@angular/*
: 7.2.9 -
@ngrx/*
: 7.3.0
Prerequisites
Before diving into building the file upload control, make sure that you have the following in place:
- An Angular 7+ application generated
- NgRx dependencies installed
- NgRx Store wired up in your application. e.g. Follow this guide
Create the Upload File Service
Let's create a brand new service in Angular
. This service will be responsible for handling the file upload from the client to the server backend. We will use the amazing HttpClient
provided with Angular
.
Generate the service
$ ng g service file-upload
Inject the HttpClient
Because we are using the HttpClient
to make requests to the backend, we need to inject it into our service. Update the constructor
line of code so that it looks as follows:
constructor(private httpClient: HttpClient) {}
Add a private field for API_BASE_URL
I typically store
API
base URLs in thesrc/environments
area. If you're interested in learning more aboutenvironments
inAngular
then check out this great article: Becoming an Angular Environmentalist
Let's create a new private field named API_BASE_URL
so that we can use this in our calls to the backend API
.
One way to accomplish this would be to do the following:
import { environment } from 'src/environments/environment';
...
private API_BASE_URL = environment.apiBaseUrl;
Add an uploadFile public method
Let's create a new public method named uploadFile
to the service. The method will take in a parameter file: File
and return an Observable<HttpEvent<{}>>
.
Typically a
get
orpost
Observable<T>
is returned from a service like this. However, in this situation, we are going to actually return the rawrequest
which is anObservable<HttpEvent<{}>>
.By returning a raw
request
we have more control over the process, to pass options likereportProgress
and allow cancellation of arequest
.
public uploadFile(file: File): Observable<HttpEvent<{}>> {
const formData = new FormData();
formData.append('files', file, file.name);
const options = {
reportProgress: true
};
const req = new HttpRequest(
'POST',
`${this.API_BASE_URL}/api/file`,
formData,
options
);
return this.httpClient.request(req);
}
Completed File Upload Service
The completed file-upload.service.ts
will look as follows:
import { HttpClient, HttpEvent, HttpRequest } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { environment } from 'src/environments/environment';
@Injectable({
providedIn: 'root'
})
export class FileUploadService {
private API_BASE_URL = environment.apiBaseUrl;
constructor(private httpClient: HttpClient) {}
public uploadFile(file: File): Observable<HttpEvent<{}>> {
const formData = new FormData();
formData.append('files', file, file.name);
const options = {
reportProgress: true
};
const req = new HttpRequest(
'POST',
`${this.API_BASE_URL}/api/file`,
formData,
options
);
return this.httpClient.request(req);
}
}
Create the Upload File Feature Store
To keep your NgRx store organized, I recommend creating a separate Upload File Feature Store. Let's bundle it all together in a module named upload-file-store.module.ts
and keep it under a sub-directory named upload-file-store
.
Create Feature Store Module
Create a feature store module using the following command:
$ ng g module upload-file-store --flat false
Create State Interface
Create a new file underneath the upload-file-store
folder, named state.ts
. The contents of the file will be as follows:
We are using a relatively new technique in that we will set up an
enum
to track the status. Thisenum
will reflect the current state of the upload process. For more information on this method, check out Alex Okrushko's article.
export enum UploadStatus {
Ready = 'Ready',
Requested = 'Requested',
Started = 'Started',
Failed = 'Failed',
Completed = 'Completed'
}
export interface State {
status: UploadStatus;
error: string | null;
progress: number | null;
}
export const initialState: State = {
status: UploadStatus.Ready,
error: null,
progress: null
};
Create Feature Actions
If you would like to learn more about NgRx Actions, then check out the official docs.
Create a new file underneath the upload-file-store
folder, named actions.ts
. This file will hold the actions we want to make available on this store.
We will create the following actions on our feature store:
UPLOAD_REQUEST
- This action is dispatched from the file upload form, it's payload will contain the actualFile
being uploaded.UPLOAD_CANCEL
- This action is dispatched from the file upload form when the cancel button is clicked. This will be used to cancel uploads in progress.UPLOAD_RESET
- This action is dispatched from the file upload form when the reset button is clicked. This will be used to reset the state of the store to defaults.UPLOAD_STARTED
- This action is dispatched from the file upload effect,HttpClient
when the API reports theHttpEventType.Sent
event.UPLOAD_PROGRESS
- This action is dispatched from the file upload effect,HttpClient
when the API reports theHttpEventType.UploadProgress
event. The payload will contain the progress percentage as a whole number.UPLOAD_FAILURE
- This action is dispatched from the file upload effect when the API returns an error, or there is anHttpEventType.ResponseHeader
orHttpEventType.Response
with anevent.status !== 200
, or when an unknownHttpEventType
is returned. The payload will contain the specific error message returned from the API and place it into anerror
field on the store.UPLOAD_COMPLETED
- This action is dispatched from the file upload effect when the API reports aHttpEventType.ResponseHeader
orHttpEventType.Response
eventevent.status === 200
. There is no payload as the API just returns a200 OK
repsonse.
The final actions.ts
file will look as follows:
import { Action } from '@ngrx/store';
export enum ActionTypes {
UPLOAD_REQUEST = '[File Upload Form] Request',
UPLOAD_CANCEL = '[File Upload Form] Cancel',
UPLOAD_RESET = '[File Upload Form] Reset',
UPLOAD_STARTED = '[File Upload API] Started',
UPLOAD_PROGRESS = '[File Upload API] Progress',
UPLOAD_FAILURE = '[File Upload API] Failure',
UPLOAD_COMPLETED = '[File Upload API] Success'
}
export class UploadRequestAction implements Action {
readonly type = ActionTypes.UPLOAD_REQUEST;
constructor(public payload: { file: File }) {}
}
export class UploadCancelAction implements Action {
readonly type = ActionTypes.UPLOAD_CANCEL;
}
export class UploadResetAction implements Action {
readonly type = ActionTypes.UPLOAD_RESET;
}
export class UploadStartedAction implements Action {
readonly type = ActionTypes.UPLOAD_STARTED;
}
export class UploadProgressAction implements Action {
readonly type = ActionTypes.UPLOAD_PROGRESS;
constructor(public payload: { progress: number }) {}
}
export class UploadFailureAction implements Action {
readonly type = ActionTypes.UPLOAD_FAILURE;
constructor(public payload: { error: string }) {}
}
export class UploadCompletedAction implements Action {
readonly type = ActionTypes.UPLOAD_COMPLETED;
}
export type Actions =
| UploadRequestAction
| UploadCancelAction
| UploadResetAction
| UploadStartedAction
| UploadProgressAction
| UploadFailureAction
| UploadCompletedAction;
Create the Feature Reducer
If you would like to learn more about NgRx Reducers, then check out the official docs.
Create a new file underneath the upload-file-store
folder, named reducer.ts
. This file will hold the reducer we create to manage state transitions to the store.
We will handle state transitions as follows for the aforementioned actions:
UPLOAD_REQUEST
- Reset the state, with the exception of settingstate.status
toUploadStatus.Requested
.UPLOAD_CANCEL
- Reset the state tree. Our effect will listen for anyUPLOAD_CANCEL
event dispatches so a specific state field is not needed for this.UPLOAD_RESET
- Reset the state tree on this action.UPLOAD_FAILURE
- Reset the state tree, with the exception of settingstate.status
toUploadStatus.Failed
andstate.error
to theerror
that was throw in thecatchError
from theAPI
in theuploadRequestEffect
effect.UPLOAD_STARTED
- Setstate.progress
to0
andstate.status
toUploadStatus.Started
.UPLOAD_PROGRESS
- Setstate.progress
to the currentaction.payload.progress
provided from the action.UPLOAD_COMPLETED
- Reset the state tree, with the exception of settingstate.status
toUploadStatus.Completed
so that the UI can display a success message.
import { Actions, ActionTypes } from './actions';
import { initialState, State, UploadStatus } from './state';
export function featureReducer(state = initialState, action: Actions): State {
switch (action.type) {
case ActionTypes.UPLOAD_REQUEST: {
return {
...state,
status: UploadStatus.Requested,
progress: null,
error: null
};
}
case ActionTypes.UPLOAD_CANCEL: {
return {
...state,
status: UploadStatus.Ready,
progress: null,
error: null
};
}
case ActionTypes.UPLOAD_RESET: {
return {
...state,
status: UploadStatus.Ready,
progress: null,
error: null
};
}
case ActionTypes.UPLOAD_FAILURE: {
return {
...state,
status: UploadStatus.Failed,
error: action.payload.error,
progress: null
};
}
case ActionTypes.UPLOAD_STARTED: {
return {
...state,
status: UploadStatus.Started,
progress: 0
};
}
case ActionTypes.UPLOAD_PROGRESS: {
return {
...state,
progress: action.payload.progress
};
}
case ActionTypes.UPLOAD_COMPLETED: {
return {
...state,
status: UploadStatus.Completed,
progress: 100,
error: null
};
}
default: {
return state;
}
}
}
Create the Feature Effects
If you would like to learn more about NgRx Effects, then check out the official docs.
Create a new file underneath the upload-file-store
folder, named effects.ts
. This file will hold the effects that we create to handle any side-effect calls to the backend API
service. This effect is where most of the magic happens in the application.
Inject Dependencies
Let's add the necessary dependencies to our constructor
as follows:
constructor(
private fileUploadService: FileUploadService,
private actions$: Actions<fromFileUploadActions.Actions>
) {}
Add a new Upload Request Effect
Effects make heavy-use of
RxJS
concepts and topics. If you are new toRxJS
then I suggest you check out the official docs
Let's create a new effect in the file named uploadRequestEffect$
.
A couple comments about what this effect is going to do:
Listen for the
UPLOAD_REQUEST
action and then make calls to thefileUploadService.uploadFile
service method to initiate the upload process.Use the
concatMap
RxJS operator here so that multiple file upload requests are queued up and processed in the order they were dispatched.Use the
takeUntil
RxJS operator listening for anUPLOAD_CANCEL
action to be dispatched. This allows us to short-circuit any requests that are in-flight.Use the
map
RxJS operator to map specificHttpEvent
responses to dispatch specificActions
that we have defined in ourStore
.Use the
catchError
RxJS operator to handle any errors that may be thrown from theHttpClient
.
The effect will look something like this:
@Effect()
uploadRequestEffect$: Observable<Action> = this.actions$.pipe(
ofType(fromFileUploadActions.ActionTypes.UPLOAD_REQUEST),
concatMap(action =>
this.fileUploadService.uploadFile(action.payload.file).pipe(
takeUntil(
this.actions$.pipe(
ofType(fromFileUploadActions.ActionTypes.UPLOAD_CANCEL)
)
),
map(event => this.getActionFromHttpEvent(event)),
catchError(error => of(this.handleError(error)))
)
)
);
Add the getActionFromHttpEvent private method
For more information on listening to progress events, check out the official docs guide from here.
This method will be responsible for mapping a specific HttpEventType
to a specific Action
that is dispatched.
HttpEventType.Sent
- This event occurs when the upload process has begun. We will dispatch anUPLOAD_STARTED
action to denote that the process has begun.HttpEventType.UploadProgress
- This event occurs when the upload process has made progress. We will dispatch anUPLOAD_PROGRESS
action with a payload ofprogress: Math.round((100 * event.loaded) / event.total)
to calculate the actual percentage complete of upload. This is because theHttpClient
returns anevent.loaded
andevent.total
property in whole number format.HttpEventType.Response
/HttpEventType.ResponseHeader
- These events occur when the upload process has finished. It is important to note that this could be a success or failure so we need to interrogate theevent.status
to check for200
. We will dispatch theUPLOAD_COMPLETED
action ifevent.status === 200
andUPLOAD_FAILURE
if theevent.status !== 200
passing theevent.statusText
as the error payload.All Others (default case) - We treat any other events that may be returned as an error because they are unexpected behavior. We will dispatch a
UPLOAD_FAILURE
action with a payload of theevent
run throughJSON.stringify
.
private getActionFromHttpEvent(event: HttpEvent<any>) {
switch (event.type) {
case HttpEventType.Sent: {
return new fromFileUploadActions.UploadStartedAction();
}
case HttpEventType.UploadProgress: {
return new fromFileUploadActions.UploadProgressAction({
progress: Math.round((100 * event.loaded) / event.total)
});
}
case HttpEventType.ResponseHeader:
case HttpEventType.Response: {
if (event.status === 200) {
return new fromFileUploadActions.UploadCompletedAction();
} else {
return new fromFileUploadActions.UploadFailureAction({
error: event.statusText
});
}
}
default: {
return new fromFileUploadActions.UploadFailureAction({
error: `Unknown Event: ${JSON.stringify(event)}`
});
}
}
}
Add the handleError private method
For more information on handling
HttpClient
errors, check out the official docs guide from here.
This method will be responsible for handling any errors that may be thrown from the HttpClient
during requests. I am making use of a neat library from npm named serialize-error
to give me a predictable error.message
no matter what type of error is thrown.
Install the library as so:
$ npm install serialize-error
import serializeError from 'serialize-error';
...
private handleError(error: any) {
const friendlyErrorMessage = serializeError(error).message;
return new fromFileUploadActions.UploadFailureAction({
error: friendlyErrorMessage
});
}
Completed Feature Effect
The completed effect will look something like this:
import { HttpEvent, HttpEventType } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Actions, Effect, ofType } from '@ngrx/effects';
import { Action } from '@ngrx/store';
import { Observable, of } from 'rxjs';
import { catchError, concatMap, map, takeUntil } from 'rxjs/operators';
import serializeError from 'serialize-error';
import { FileUploadService } from 'src/app/_services';
import * as fromFileUploadActions from './actions';
@Injectable()
export class UploadFileEffects {
@Effect()
uploadRequestEffect$: Observable<Action> = this.actions$.pipe(
ofType(fromFileUploadActions.ActionTypes.UPLOAD_REQUEST),
concatMap(action =>
this.fileUploadService.uploadFile(action.payload.file).pipe(
takeUntil(
this.actions$.pipe(
ofType(fromFileUploadActions.ActionTypes.UPLOAD_CANCEL)
)
),
map(event => this.getActionFromHttpEvent(event)),
catchError(error => of(this.handleError(error)))
)
)
);
constructor(
private fileUploadService: FileUploadService,
private actions$: Actions<fromFileUploadActions.Actions>
) {}
private getActionFromHttpEvent(event: HttpEvent<any>) {
switch (event.type) {
case HttpEventType.Sent: {
return new fromFileUploadActions.UploadStartedAction();
}
case HttpEventType.UploadProgress: {
return new fromFileUploadActions.UploadProgressAction({
progress: Math.round((100 * event.loaded) / event.total)
});
}
case HttpEventType.ResponseHeader:
case HttpEventType.Response: {
if (event.status === 200) {
return new fromFileUploadActions.UploadCompletedAction();
} else {
return new fromFileUploadActions.UploadFailureAction({
error: event.statusText
});
}
}
default: {
return new fromFileUploadActions.UploadFailureAction({
error: `Unknown Event: ${JSON.stringify(event)}`
});
}
}
}
private handleError(error: any) {
const friendlyErrorMessage = serializeError(error).message;
return new fromFileUploadActions.UploadFailureAction({
error: friendlyErrorMessage
});
}
}
Create the Feature Selectors
If you would like to learn more about NgRx Selectors, then check out the official docs.
Create a new file underneath the upload-file-store
folder, named selectors.ts
. This file will hold the selectors we will use to pull specific pieces of state out of the store. These are technically not required, but strongly encouraged. Selectors improve application performance with the use of the MemoizedSelector
wrapper. Selectors also simplify UI logic.
We will create a selector for each significant property of the state. This includes the following properties:
-
state.status
- Since this is anenum
we will create a selector for eachenum
choice. state.error
state.progress
The completed selectors file will look something like the following:
import {
createFeatureSelector,
createSelector,
MemoizedSelector
} from '@ngrx/store';
import { State, UploadStatus } from './state';
const getError = (state: State): string => state.error;
const getStarted = (state: State): boolean =>
state.status === UploadStatus.Started;
const getRequested = (state: State): boolean =>
state.status === UploadStatus.Requested;
const getReady = (state: State): boolean => state.status === UploadStatus.Ready;
const getProgress = (state: State): number => state.progress;
const getInProgress = (state: State): boolean =>
state.status === UploadStatus.Started && state.progress >= 0;
const getFailed = (state: State): boolean =>
state.status === UploadStatus.Failed;
const getCompleted = (state: State): boolean =>
state.status === UploadStatus.Completed;
export const selectUploadFileFeatureState: MemoizedSelector<
object,
State
> = createFeatureSelector<State>('uploadFile');
export const selectUploadFileError: MemoizedSelector<
object,
string
> = createSelector(
selectUploadFileFeatureState,
getError
);
export const selectUploadFileReady: MemoizedSelector<
object,
boolean
> = createSelector(
selectUploadFileFeatureState,
getReady
);
export const selectUploadFileRequested: MemoizedSelector<
object,
boolean
> = createSelector(
selectUploadFileFeatureState,
getRequested
);
export const selectUploadFileStarted: MemoizedSelector<
object,
boolean
> = createSelector(
selectUploadFileFeatureState,
getStarted
);
export const selectUploadFileProgress: MemoizedSelector<
object,
number
> = createSelector(
selectUploadFileFeatureState,
getProgress
);
export const selectUploadFileInProgress: MemoizedSelector<
object,
boolean
> = createSelector(
selectUploadFileFeatureState,
getInProgress
);
export const selectUploadFileFailed: MemoizedSelector<
object,
boolean
> = createSelector(
selectUploadFileFeatureState,
getFailed
);
export const selectUploadFileCompleted: MemoizedSelector<
object,
boolean
> = createSelector(
selectUploadFileFeatureState,
getCompleted
);
Update the Feature Module
We now need to update the feature module UploadFileStoreModule
to wire-up the store.
The completed UploadFileStoreModule
should look similar to this:
import { CommonModule } from '@angular/common';
import { NgModule } from '@angular/core';
import { EffectsModule } from '@ngrx/effects';
import { StoreModule } from '@ngrx/store';
import { UploadFileEffects } from './effects';
import { featureReducer } from './reducer';
@NgModule({
declarations: [],
imports: [
CommonModule,
StoreModule.forFeature('uploadFile', featureReducer),
EffectsModule.forFeature([UploadFileEffects])
]
})
export class UploadFileStoreModule {}
Import this module where needed
Make sure to import this new UploadFileStoreModule
where it is needed. In this example, we will import this into the AppModule
as we do not have any lazy-loaded features.
Update your AppModule to import Store & Effects
Last, make sure that you update your AppModule
to import the StoreModule.forRoot
and EffectsModule.forRoot
.
An updated AppModule
may look as follows:
import { HttpClientModule } from '@angular/common/http';
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { EffectsModule } from '@ngrx/effects';
import { StoreModule } from '@ngrx/store';
import { StoreDevtoolsModule } from '@ngrx/store-devtools';
import { environment } from 'src/environments/environment';
import { AppComponent } from './app.component';
import { UploadFileStoreModule } from './upload-file-store/upload-file-store.module';
@NgModule({
declarations: [AppComponent],
imports: [
BrowserModule,
HttpClientModule,
StoreModule.forRoot({}),
EffectsModule.forRoot([]),
StoreDevtoolsModule.instrument({
maxAge: 25, // Retains last 25 states
logOnly: environment.production // Restrict extension to log-only mode
}),
UploadFileStoreModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule {}
Let's Review So Far
Up to this point, we have created a new
FileUploadService
that calls our backendAPI
to upload aFile
object.We have also created a new
UploadFileStore
feature store that providesActions
, aReducer
,Effects
, andSelectors
to manage the file upload process.Last, the store has been imported into our
AppModule
for use.
Now that we have the foundation laid out for us we can turn our attention to the user interface and wire-up a new component to the UploadFileStore
that we created to manage our process.
This will be the fun part!
Create the Upload File Component
Let's start by creating a brand-new Component
. This component will consist of the following elements:
An
input
element for the user to interact with to upload a file. Thechange
event will dispatch theUploadFileStoreActions.UploadRequest()
actionA progress percentage to connected to the
UploadFileStoreSelectors.selectUploadFileProgress
selector for real-time progressA Cancel UPload button to dispatch the
UploadFileStoreActions.UploadCancelRequest()
actionAn Upload Another File button to dispatch the
UploadFileStoreActions.UploadResetRequest()
action and allow for a new file upload
SIDE NOTE: This would be a good scenario to create a connected container with a dumb component, but for the brevity of this article I will show these combined as one. In the example repository, I will show both scenarios.
Generate the component
Click here for more details on using the powerful Angular CLI
$ ng g component upload-file
For simplicity of this article we will just display the progress percentage, this could easily be adapted to hook into the
value
property of a progress bar control, like the Angular Material library provides.
Update the component *.ts file
Inject the Store
We need to wire-up our store into this component for use. Let's start by injecting the store into the constructor
. The finished constructor
should look something like this:
...
constructor(private store$: Store<fromFileUploadState.State>) {}
Wire-up our selectors from state
Let's create six (6) public fields on the component. A good practice is to place $
as a suffix so that you know these are Observable
and must be subscribed to in the template.
completed$: Observable<boolean>;
progress$: Observable<number>;
error$: Observable<string>;
isInProgress$: Observable<boolean>;
isReady$: Observable<boolean>;
hasFailed$: Observable<boolean>;
Let's hook these up to the store in our ngOnInit
life-cycle hook.
ngOnInit() {
this.completed$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileCompleted)
);
this.progress$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileProgress)
);
this.error$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileError)
);
this.isInProgress$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileInProgress)
);
this.isReady$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileReady)
);
this.hasFailed$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileFailed)
);
}
Wire-up our action dispatchers
Let's add uploadFile
, resetUpload
, and cancelUpload
methods to connect our button clicks to dispatch actions in the store.
uploadFile(event: any) {
const files: FileList = event.target.files;
const file = files.item(0);
this.store$.dispatch(
new fromFileUploadActions.UploadRequestAction({
file
})
);
// clear the input form
event.srcElement.value = null;
}
resetUpload() {
this.store$.dispatch(new UploadFileStoreActions.UploadResetAction());
}
cancelUpload() {
this.store$.dispatch(new UploadFileStoreActions.UploadCancelAction());
}
Finished Component *.ts file
The finished component *.ts file should look similar to the following:
import { Component, OnInit } from '@angular/core';
import { select, Store } from '@ngrx/store';
import { Observable } from 'rxjs';
import * as fromFileUploadActions from 'src/app/upload-file-store/actions';
import * as fromFileUploadSelectors from 'src/app/upload-file-store/selectors';
import * as fromFileUploadState from 'src/app/upload-file-store/state';
@Component({
selector: 'app-upload-file',
templateUrl: './upload-file.component.html',
styleUrls: ['./upload-file.component.css']
})
export class UploadFileComponent implements OnInit {
completed$: Observable<boolean>;
progress$: Observable<number>;
error$: Observable<string>;
isInProgress$: Observable<boolean>;
isReady$: Observable<boolean>;
hasFailed$: Observable<boolean>;
constructor(private store$: Store<fromFileUploadState.State>) {}
ngOnInit() {
this.completed$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileCompleted)
);
this.progress$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileProgress)
);
this.error$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileError)
);
this.isInProgress$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileInProgress)
);
this.isReady$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileReady)
);
this.hasFailed$ = this.store$.pipe(
select(fromFileUploadSelectors.selectUploadFileFailed)
);
}
uploadFile(event: any) {
const files: FileList = event.target.files;
const file = files.item(0);
this.store$.dispatch(
new fromFileUploadActions.UploadRequestAction({
file
})
);
// clear the input form
event.srcElement.value = null;
}
resetUpload() {
this.store$.dispatch(new fromFileUploadActions.UploadResetAction());
}
cancelUpload() {
this.store$.dispatch(new fromFileUploadActions.UploadCancelAction());
}
}
Update the component *.html template
We are going to add five (5) major parts to our upload file component.
Add the input field
There is no upload file button, rather we will make use of the built-in input component and hook to the change
event. Any time a file is added to the form this event will fire. We also only want to display this form if we are accepting new files to be uploaded, i.e. it has failed or it is ready. We will use the *ngIf
structural directive to help here referencing our isReady$
and hasFailed$
observables.
<div class="message" *ngIf="(isReady$ | async) || (hasFailed$ | async)">
<input #file type="file" multiple (change)="uploadFile($event)" />
</div>
Add the progress message
This message will be displayed when the progress is greater than or equal to 0% and the UploadStatus
is Failed
. We will use *ngIf
to only display if it's in this state using the isInProgress$
selector value. We will set the text of the progress message to the progress$
selector value.
<div class="message" *ngIf="(isInProgress$ | async)">
<div style="margin-bottom: 14px;">Uploading... {{ progress$ | async }}%</div>
</div>
Add the Cancel Upload button
This button will utilize the *ngIf
to only display if the upload is in progress using the isInProgress$
selector value. The click event will trigger the dispatch of the UploadCancelAction
.
<div class="message" *ngIf="(isInProgress$ | async)">
<button (click)="cancelUpload()">Cancel Upload</button>
</div>
Add the Reset Upload button
This button will utilize the *ngIf
to only display if the upload is complete using the completed$
selector value. The click event will trigger the dispatch of the UploadResetAction
.
<div class="message" *ngIf="(completed$ | async)">
<h4>
File has been uploaded successfully!
</h4>
<button (click)="resetUpload()">Upload Another File</button>
</div>
Add the Error message
This button will utilize the *ngIf
to only display if hasFailed$
selector value returns true
. The actual error message is pulled from the error$
selector value.
<div class="message error" *ngIf="(hasFailed$ | async)">
Error: {{ error$ | async }}
</div>
Finished Component *.html file
<div class="message" *ngIf="(isReady$ | async) || (hasFailed$ | async)">
<input #file type="file" multiple (change)="uploadFile($event)" />
</div>
<div class="message" *ngIf="(isInProgress$ | async)">
<div style="margin-bottom: 14px;">Uploading... {{ progress$ | async }}%</div>
</div>
<div class="message" *ngIf="(isInProgress$ | async)">
<button (click)="cancelUpload()">Cancel Upload</button>
</div>
<div class="message" *ngIf="(completed$ | async)">
<h4>
File has been uploaded successfully!
</h4>
<button (click)="resetUpload()">Upload Another File</button>
</div>
<div class="message error" *ngIf="(hasFailed$ | async)">
Error: {{ error$ | async }}
</div>
Add some styles to our Component *.css file
For formatting let's add a few simple classes to our component stylesheet:
.message {
margin-bottom: 15px;
}
.error {
color: red;
}
Add the Component to our AppComponent
For the purposes of this article we will add our new UploadFileComponent
component to our AppComponent
. The template will look as follows:
<app-upload-file></app-upload-file>
(Bonus Feature) Back-end REST Endpoint
For a full mock back-end server checkout my [repository here:
For those of you brave souls that have made it this far... You might be asking what the backend API
endpoint looks like. Well, here's an example ASP.NET Core
Controller
offered free of charge ;-)
public class FileController : ControllerBase
{
[HttpPost("")]
public async Task<IActionResult> Post(List<IFormFile> files)
{
try
{
foreach (var file in files)
{
Console.WriteLine($"Begin Uploaded File: {file.FileName}");
//simulate upload
Task.Delay(5000).Wait();
Console.WriteLine($"Finished Uploaded File: {file.FileName}");
}
return Ok();
}
catch (Exception ex)
{
return BadRequest($"Unable to upload file(s).");
}
}
}
GitHub Example Repository
I always like to provide working code examples that follow the article. You can find this articles companion application at the following repository:
Conclusion
It's important to remember that I have implemented these best practices in several "real world" applications. While I have found these best practices helpful, and maintainable, I do not believe they are an end-all-be-all solution to your NgRx projects; it's just what has worked for me. I am curious as to what you all think? Please feel free to offer any suggestions, tips, or best practices you've learned when building enterprise Angular applications with NgRx and I will update the article to reflect as such. Happy Coding!
Additional Resources
I would highly recommend enrolling in the Ultimate Angular courses, especially the NgRx course. It is well worth the money and I have used it as a training tool for new Angular developers. Follow the link below to signup.
Ultimate Courses: Expert online courses in JavaScript, Angular, NGRX and TypeScript
Top comments (3)
Really great article. The timing on this is perfect. I was actually just going to be looking up the
FormData
to see if that can be used withHttpClient
and blamo -- you've got it right there! A very interesting exploration. To be honest, all the NgRx stuff kind of goes over my head; but, I got the general idea. This gives me some good ideas for some subsequent exploration.Thanks Ben! Glad it was helpful!
Great Article. Does you have crud image with @ngrx/data ? I want to combine upload image and manage image in one lazy module. But too hard for me. Really need advice from you. thanks o( ̄▽ ̄)ブ