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    apollo-link
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    1.2.14 • Public • Published

    apollo-link

    Purpose

    apollo-link is a standard interface for modifying control flow of GraphQL requests and fetching GraphQL results, designed to provide a simple GraphQL client that is capable of extensions. The targeted use cases of apollo-link are highlighted below:

    • fetch queries directly without normalized cache
    • network interface for Apollo Client
    • network interface for Relay Modern
    • fetcher for

    Apollo Link is the interface for creating new links in your application.

    The client sends a request as a method call to a link and can recieve one or more (in the case of subscriptions) responses from the server. The responses are returned using the Observer pattern.

    Apollo Link Chain

    Results from the server can be provided by calling next(result) on the observer. In the case of a network/transport error (not a GraphQL Error) the error(err) method can be used to indicate a response will not be recieved. If multiple responses are not supported by the link, complete() should be called to inform the client no further data will be provided.

    In the case of an intermediate link, a second argument to request(operation, forward) is the link to forward(operation) to. forward returns an observable and it can be returned directly or subscribed to.

    forward(operation).subscribe({
      next: result => {
        handleTheResult(result)
      },
      error: error => {
        handleTheNetworkError(error)
      },
    });

    Implementing a basic custom transport

    import { ApolloLink, Observable } from 'apollo-link';
     
    export class CustomApolloLink extends ApolloLink {
      request(operation /*, forward*/) {
        //Whether no one is listening anymore
        let unsubscribed = false;
     
        return new Observable(observer => {
          somehowGetOperationToServer(operation, (error, result) => {
            if (unsubscribed) return;
            if (error) {
              //Network error
              observer.error(error);
            } else {
              observer.next(result);
              observer.complete(); //If subscriptions not supported
            }
          });
     
          function unsubscribe() {
            unsubscribed = true;
          }
     
          return unsubscribe;
        });
      }
    }

    Installation

    npm install apollo-link --save

    Keywords

    none

    Install

    npm i apollo-link

    DownloadsWeekly Downloads

    2,465,337

    Version

    1.2.14

    License

    MIT

    Unpacked Size

    100 kB

    Total Files

    42

    Last publish

    Collaborators

    • jbaxleyiii
    • peggyrayzis
    • apollo-bot