Is it possible to implement lazy loading for data in TypeScript classes?

Question

Is it possible to implement lazy loading for data in TypeScript classes?

Looking to optimize my Angular application's data structure when consuming a RESTful API. My goal is to only load necessary data from the server on demand.

For instance, if I have a collection of Building objects each with a set of tenant IDs in an array instead of full Tenant objects. This way, when listing buildings in the app, I can display basic details and fetch individual tenant information from the API asynchronously only when needed. It helps avoid fetching all tenants upfront for every building.

Is this a common approach in web applications? Struggling to find resources on this specific topic, especially implementations tailored for Angular.

Appreciate any insights or Angular-specific examples on implementing this strategy!

angular rest typescript

Answer 1

Answer №1

I've been pondering this same dilemma myself. Here are a few potential strategies:

Load everything at once - Simply retrieve all the data from your REST server upfront, as you mentioned. While this is convenient, it may not scale well with nested data structures or large amounts of data. However, it could be suitable if the data is only used at a single nesting level and is relatively small for each object, or if performance and bandwidth concerns are minimal.

The other options explore asynchronous approaches to retrieving data, where the Building REST route returns the Building object along with a TenantsURL for accessing the tenant list.

Lazy TypeScript getters: Conceal the variable behind a getter in your class:
```
class Building {

    public constructor(private readonly httpService: HttpClient){}

    public get tenants(): Observable<Tenant[]> {
        return this.httpService.get<Tenant[]>([url here]);
    }

}
```
A drawback here is that using tenants in an HTML template will cause angular to call this getter function during each change detection step, potentially adding costs depending on latency and data size. Another downside is the requirement for the HttpClient Service (or a custom service) injected into your models, blurring the line between services and models.
Standalone Get Function: A slight tweak to #2, creating a class method in your model that can be called:
```
class Building {

    public constructor(){}

    public getTenants(httpService: HttpClient): Observable<Tenant[]> {
        return httpService.get<Tenant[]>([url here]);
    }

}
```
This shifts the responsibility for providing the "getter" service (HttpClient in this case) from model construction to whoever needs to access the tenants, such as an Angular component. You can then use an Async pipe in an HTML template to display the values, or subscribe in an Angular component. However, since this is a function, it will be invoked during every change detection cycle, impacting performance.
Pipe: Create a custom async pipe, TenantPipe, allowing injection of necessary services to retrieve Tenant data from a Building (https://angular.io/guide/pipes). You can then apply the pipe on the Building in an HTML template to asynchronously fetch the list of tenants. By separating models from the async retrieval functionality, angular will execute the pipe only once per change detection cycle. While more focused on HTML templates, pipes can also be injected into component typescript for similar functionality.

Service: Develop a service, TenantService, featuring a method
```
getTenantFromBuilding(building: Building): Observable<Tenant[]>
```
. Utilize this in your typescript components wherever needed. This approach mirrors #4 but encapsulates the functionality within a service rather than a pipe with injected services. More oriented towards Typescript, the returned value from the service can still be displayed in an HTML template.

Each approach carries its own advantages and drawbacks, so choosing the right one depends on the context at hand.

Answer 2

I've been pondering this same dilemma myself. Here are a few potential strategies:

Load everything at once - Simply retrieve all the data from your REST server upfront, as you mentioned. While this is convenient, it may not scale well with nested data structures or large amounts of data. However, it could be suitable if the data is only used at a single nesting level and is relatively small for each object, or if performance and bandwidth concerns are minimal.

The other options explore asynchronous approaches to retrieving data, where the Building REST route returns the Building object along with a TenantsURL for accessing the tenant list.

Lazy TypeScript getters: Conceal the variable behind a getter in your class:
```
class Building {

    public constructor(private readonly httpService: HttpClient){}

    public get tenants(): Observable<Tenant[]> {
        return this.httpService.get<Tenant[]>([url here]);
    }

}
```
A drawback here is that using tenants in an HTML template will cause angular to call this getter function during each change detection step, potentially adding costs depending on latency and data size. Another downside is the requirement for the HttpClient Service (or a custom service) injected into your models, blurring the line between services and models.
Standalone Get Function: A slight tweak to #2, creating a class method in your model that can be called:
```
class Building {

    public constructor(){}

    public getTenants(httpService: HttpClient): Observable<Tenant[]> {
        return httpService.get<Tenant[]>([url here]);
    }

}
```
This shifts the responsibility for providing the "getter" service (HttpClient in this case) from model construction to whoever needs to access the tenants, such as an Angular component. You can then use an Async pipe in an HTML template to display the values, or subscribe in an Angular component. However, since this is a function, it will be invoked during every change detection cycle, impacting performance.
Pipe: Create a custom async pipe, TenantPipe, allowing injection of necessary services to retrieve Tenant data from a Building (https://angular.io/guide/pipes). You can then apply the pipe on the Building in an HTML template to asynchronously fetch the list of tenants. By separating models from the async retrieval functionality, angular will execute the pipe only once per change detection cycle. While more focused on HTML templates, pipes can also be injected into component typescript for similar functionality.

Service: Develop a service, TenantService, featuring a method
```
getTenantFromBuilding(building: Building): Observable<Tenant[]>
```
. Utilize this in your typescript components wherever needed. This approach mirrors #4 but encapsulates the functionality within a service rather than a pipe with injected services. More oriented towards Typescript, the returned value from the service can still be displayed in an HTML template.

Each approach carries its own advantages and drawbacks, so choosing the right one depends on the context at hand.

Is it possible to implement lazy loading for data in TypeScript classes?

Answer №1

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