Package org.polkadot.api.rx

Class ApiRx

  • All Implemented Interfaces:
    Types.ApiBaseInterface<io.reactivex.Observable>, IApi<io.reactivex.Observable>
    public class ApiRx
extends ApiBase<io.reactivex.Observable>
    # @polkadot/api/rx

    ## Overview

    ApiRx is a powerfull RxJS Observable wrapper around the RPC and interfaces on the Polkadot network. As a full Observable API, all interface calls return RxJS Observables, including the static `.create(...)`. In the same fashion and subscription-based methods return long-running Observables that update with the latest values.

    The API is well suited to real-time applications where the latest state is needed, unlocking the subscription-based features of Polkadot (and Substrate) clients. Some familiarity with RxJS is a requirement to use the API, however just understanding `.subscribe` and `.pipe` on Observables will unlock full-scale use thereof.

    ## Usage

    Making rpc calls -

    ```java import org.polkadot.api.rx.ApiRx;

    // initialise via Promise & static create ApiRx api = ApiRx.create().toPromise();

    // make a call to retrieve the current network head api.rpc.chain.subscribeNewHead().subscribe((header) => { System.out.print("Chain is at "); System.out.println(header.blockNumber); }); ``` Subscribing to chain state -

    ```java import org.polkadot.api.rx.ApiRx;

    // initialise a provider with a specific endpoint WsProvider provider = new WsProvider('wss://example.com:9944')

    // initialise via isReady & new with specific provider new ApiRx(provider) .isReady .pipe( switchMap((api) => combineLatest([ api.query.timestamp.blockPeriod(), api.query.timestamp.now().pipe(pairwise()) ]) ) ) .subscribe(([blockPeriod, timestamp]) => { int elapsed = timestamp[1] - timestamp[0]; System.out.printf("timestamp %d \nelapsed %d \n(%d target)", timestamp[1], elapsed, blockPeriod); });

    Submitting a transaction -

    ```java import org.polkadot.api.rx.ApiRx;

    const keyring = testingPairs();

    // get api via Promise ApiRx api = ApiRx.create().toPromise();

    // retrieve nonce for the account api.query.system .accountNonce(keyring.alice.address()) .pipe( first(), // pipe nonce into transfer switchMap((nonce) => api.tx.balances // create transfer .transfer(keyring.bob.address(), 12345) // sign the transcation .sign(keyring.alice, { nonce }) // send the transaction .send() ) ) // subscribe to overall result .subscribe(({ status }) => { if (status.isFinalized) { System.out.print("Completed at block hash "); System.out.println(status.asFinalized.toHex()); } }); ```

    • Method Detail

      • create

        public static io.reactivex.Observable<ApiRx> create​(IProvider provider)
        Creates an ApiRx instance using the supplied provider. Returns an Observable containing the actual Api instance.
        Parameters:
        provider - provider that is passed to the class contructor

        **Example**

        ```java import org.polkadot.api.rx.ApiRx;

        ApiRx.create() .pipe( switchMap((api) => api.rpc.chain.subscribeNewHead() )) .subscribe((header) => { System.out.print("new block "); System.out.println(header.blockNumber); }); ```