Angular - Delay template loading until data is received

Question

Angular - Delay template loading until data is received

I am currently working on a component that dynamically renders several components using the following template:

<div [saJquiAccordion]="{active: group.value['collapsed']}" *ngFor="let group of filterGroupsTemplate | keysCheckDisplay;">
    <div>
        <h4>{{group.key | i18n}}</h4>
        <form id="ibo-{{group.key}}" class="form-horizontal" autocomplete="off" style="overflow: initial">
            <fieldset *ngFor="let field of group.value | keys">
                <ng-container *ngComponentOutlet="fieldSets[field.value.template];
                                    ngModuleFactory: smartadminFormsModule;"></ng-container>
            </fieldset>
        </form>
    </div>
</div>

The challenge I'm facing is that the data required to populate these components is fetched from an API call:

      this.getFiltersSubscription = this.getFilters().subscribe(
            (filters) => {
                this.filters = filters;
                log.info('API CALL. getting filters');

                // Sending data to fieldform components
                this.iboService.updateIBOsRankList(filters['iboRank'].data);
                this.iboService.updateIBOsNewsletterOptions(filters['iboNewsletter'].data);
                this.iboService.updateIBOsTotalOrders(filters['iboTotalOrders'].data);
            }
        );

After obtaining the data, I activate a service Observable that my components subscribe to for processing the collected data.

ISSUE

If the API call happens before all components are loaded, the service methods will be triggered with no subscribers.

A potential solution would involve loading the data first, rendering the template only when the data is loaded, and then triggering the service methods (Observables).

I aim to avoid making multiple API calls for each component, considering there could be around 60 components to load. Instead, I prefer a more streamlined approach like this:

// Listens for field initialization and triggers the creation of the fieldset by initiating a service call that will be listened to by the field component
        this.iboService.initIBOsFilters$.subscribe(
            (fieldName) => {
                if (fieldName === 'IBOsRankSelectorFieldComponent') {
                    log.data('inside initIBOsFilters$ subscription, calling updateIBOsFilters()', fieldName);
                    this.iboService.updateIBOsRankList(this.filters['iboRank'].data); // HERE I'M PASSING DATA TO THE DYNAMICALLY RENDERED COMPONENT. HOWEVER, IF this.filters IS UNDEFINED, IT WILL CAUSE AN ISSUE
                }
            }
        );

To achieve this, it is crucial to ensure that this.filters is defined. This leads me to the question:

How can I delay rendering my template HTML until after the API call is completed and this.filters is defined?

I apologize for the lengthy explanation, but please feel free to ask for more details if needed.

Thank you!

angular typescript

Answer 1

Answer №1

Upon exploring various suggestions provided by people, I eventually stumbled upon the solution involving the async pipe. However, grasping how to implement it did prove to be a bit of a challenge.

Here is the solution:

// Declaring the Promise, yes! Promise!
filtersLoaded: Promise<boolean>;

// Later in the Component, where I fetch the data, I resolve() the Promise
this.getFiltersSubscription = this.getFilters().subscribe(
    (filters) => {
        this.filters = filters;
        log.info('API CALL. getting filters');

        this.filtersLoaded = Promise.resolve(true); // Resolving the Promise once the necessary data is obtained
    }
);

// In this listener triggered by the dynamic components when instanced,
// I pass the data and know that it is defined due to the template change

// Listens to field's init and creates the fieldset triggering a service call
// that will be listened by the field component
this.iboService.initIBOsFilters$.subscribe(
    (fieldName) => {
        if (fieldName === 'IBOsRankSelectorFieldComponent') {
            log.data('inside initIBOsFilters$ subscription, calling updateIBOsFilters()', fieldName);
            this.iboService.updateIBOsRankList(this.filters['iboRank'].data);
        }
    }
);

In the template, the async pipe is used with an Observable or a Promise

<div *ngIf="filtersLoaded | async">
    <div [saJquiAccordion]="{active: group.value['collapsed']}" *ngFor="let group of filterGroupsTemplate | keysCheckDisplay;">
        <div>
            <h4>{{group.key | i18n}}</h4>
            <form id="ibo-{{group.key}}" class="form-horizontal" autocomplete="off" style="overflow: initial">
                <fieldset *ngFor="let field of group.value | keys">
                    <ng-container *ngComponentOutlet="fieldSets[field.value.template];
                                    ngModuleFactory: smartadminFormsModule;"></ng-container>
                </fieldset>
            </form>
        </div>
    </div>
</div>

Important Note:

The async pipe requires an Observable or a Promise for functionality, which led me to create a Promise in this scenario.
I opted not to use the resolver approach as it is typically utilized when navigating to a component via Angular's routing system. Since this component is part of a larger one and not instantiated through routing like a regular component, I decided against using that method. (Although I did experiment with it briefly, it didn't yield the desired outcome)

Answer 2

Upon exploring various suggestions provided by people, I eventually stumbled upon the solution involving the async pipe. However, grasping how to implement it did prove to be a bit of a challenge.

Here is the solution:

// Declaring the Promise, yes! Promise!
filtersLoaded: Promise<boolean>;

// Later in the Component, where I fetch the data, I resolve() the Promise
this.getFiltersSubscription = this.getFilters().subscribe(
    (filters) => {
        this.filters = filters;
        log.info('API CALL. getting filters');

        this.filtersLoaded = Promise.resolve(true); // Resolving the Promise once the necessary data is obtained
    }
);

// In this listener triggered by the dynamic components when instanced,
// I pass the data and know that it is defined due to the template change

// Listens to field's init and creates the fieldset triggering a service call
// that will be listened by the field component
this.iboService.initIBOsFilters$.subscribe(
    (fieldName) => {
        if (fieldName === 'IBOsRankSelectorFieldComponent') {
            log.data('inside initIBOsFilters$ subscription, calling updateIBOsFilters()', fieldName);
            this.iboService.updateIBOsRankList(this.filters['iboRank'].data);
        }
    }
);

In the template, the async pipe is used with an Observable or a Promise

<div *ngIf="filtersLoaded | async">
    <div [saJquiAccordion]="{active: group.value['collapsed']}" *ngFor="let group of filterGroupsTemplate | keysCheckDisplay;">
        <div>
            <h4>{{group.key | i18n}}</h4>
            <form id="ibo-{{group.key}}" class="form-horizontal" autocomplete="off" style="overflow: initial">
                <fieldset *ngFor="let field of group.value | keys">
                    <ng-container *ngComponentOutlet="fieldSets[field.value.template];
                                    ngModuleFactory: smartadminFormsModule;"></ng-container>
                </fieldset>
            </form>
        </div>
    </div>
</div>

Important Note:

The async pipe requires an Observable or a Promise for functionality, which led me to create a Promise in this scenario.
I opted not to use the resolver approach as it is typically utilized when navigating to a component via Angular's routing system. Since this component is part of a larger one and not instantiated through routing like a regular component, I decided against using that method. (Although I did experiment with it briefly, it didn't yield the desired outcome)

Answer 3

Answer №2

To ensure that the data is loaded or filters are initialized before the route is activated, consider using a resolver.

Visit this link for more information:

You can also learn about resolvers in Angular by checking out this link: https://angular.io/api/router/Resolve

Answer 4

To ensure that the data is loaded or filters are initialized before the route is activated, consider using a resolver.

Visit this link for more information:

You can also learn about resolvers in Angular by checking out this link: https://angular.io/api/router/Resolve

Answer 5

Answer №3

<p class="p-large">{{homeData?.meta[0].site_desc}}</p>

Using a conditional operator "?" after the variable to handle data loading from the server.

home.component.ts

import { Component, OnInit } from '@angular/core';
import { HomeService } from '../services/home.service';

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.scss']
})
export class HomeComponent implements OnInit {
  public homeData: any;
  constructor(private homeService: HomeService) {}

  ngOnInit(): void {
    this.homeService.getHomeData().subscribe( data => {
      this.homeData = data[0];
    }, error => {
      console.log(error);
    });
  }
}

Answer 6

<p class="p-large">{{homeData?.meta[0].site_desc}}</p>

Using a conditional operator "?" after the variable to handle data loading from the server.

home.component.ts

import { Component, OnInit } from '@angular/core';
import { HomeService } from '../services/home.service';

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.scss']
})
export class HomeComponent implements OnInit {
  public homeData: any;
  constructor(private homeService: HomeService) {}

  ngOnInit(): void {
    this.homeService.getHomeData().subscribe( data => {
      this.homeData = data[0];
    }, error => {
      console.log(error);
    });
  }
}

Answer 7

Answer №4

To replace the use of async, you can create a variable called isLoading = true. Display a spinner provided by Angular while this variable is true instead of showing content using *ngIf. Once your subscription activates, set isLoading = false. This approach helps avoid errors related to missing data because technically the content that relies on it won't be rendered until it exists.

Answer 8

To replace the use of async, you can create a variable called isLoading = true. Display a spinner provided by Angular while this variable is true instead of showing content using *ngIf. Once your subscription activates, set isLoading = false. This approach helps avoid errors related to missing data because technically the content that relies on it won't be rendered until it exists.

Answer 9

Answer №5

Although I may be a bit late to the party, what has been effective for me is incorporating a loading boolean into my state within the reducer.

In the reducer.ts file:

export interface State {
 things: Stuff;
 loaded: boolean;
}

export const reducers: ActionReducerMap<State> = {
    things: reducer,
    loaded: loadedReducer,
};

Ensure to export the loaded function so it switches to true once the state is returned.

export function loadedReducer(state: boolean = false, action: ThingActions): boolean {
    switch (action.type) {
        case ThingActionTypes.GetThings:
            return true;
    }
    return state;
}

Then in your Typescript file, subscribe to the loaded state.

In parent.component.ts:

this.loaded$ = this.store.pipe(select(fromReducer.loaded));

Utilize this similar to an async pipe in your template.

In parent.component.html:

        <ng-container *ngIf="(loaded$ | async); else loading">
            <child-component></child-component>
        </ng-container>
        <ng-template #loading></ng-template>

Answer 10

Although I may be a bit late to the party, what has been effective for me is incorporating a loading boolean into my state within the reducer.

In the reducer.ts file:

export interface State {
 things: Stuff;
 loaded: boolean;
}

export const reducers: ActionReducerMap<State> = {
    things: reducer,
    loaded: loadedReducer,
};

Ensure to export the loaded function so it switches to true once the state is returned.

export function loadedReducer(state: boolean = false, action: ThingActions): boolean {
    switch (action.type) {
        case ThingActionTypes.GetThings:
            return true;
    }
    return state;
}

Then in your Typescript file, subscribe to the loaded state.

In parent.component.ts:

this.loaded$ = this.store.pipe(select(fromReducer.loaded));

Utilize this similar to an async pipe in your template.

In parent.component.html:

        <ng-container *ngIf="(loaded$ | async); else loading">
            <child-component></child-component>
        </ng-container>
        <ng-template #loading></ng-template>

Answer 11

Answer №6

**Note: The following method is not ideal, but it can be used as a quick fix: **

A simple solution would be to enclose it in an ngIf statement. While this may not be the best practice, it does resolve the issue at hand.

The specific error in this case is: "Title of undefined"

<div *ngIf="form">
  {{form.Title}}
</div>

Answer 12

**Note: The following method is not ideal, but it can be used as a quick fix: **

A simple solution would be to enclose it in an ngIf statement. While this may not be the best practice, it does resolve the issue at hand.

The specific error in this case is: "Title of undefined"

<div *ngIf="form">
  {{form.Title}}
</div>

Angular - Delay template loading until data is received

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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