40 lines
1.3 KiB
TypeScript
40 lines
1.3 KiB
TypeScript
// Copyright 2017-2019 @polkadot/api-derive authors & contributors
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// This software may be modified and distributed under the terms
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// of the Apache-2.0 license. See the LICENSE file for details.
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import { AccountId } from '@polkadot/types/interfaces';
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import { ApiInterfaceRx } from '@polkadot/api/types';
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import { Observable, combineLatest } from 'rxjs';
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import { map } from 'rxjs/operators';
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import { Vec } from '@polkadot/types';
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import { HeaderExtended } from '../type';
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import { drr, memo } from '../util';
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/**
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* @name subscribeNewHeads
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* @returns An array containing the block header and the block author
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* @description An observable of the current block header and it's author
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* @example
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* <BR>
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*
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* ```javascript
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* api.derive.chain.subscribeNewHeads((header) => {
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* console.log(`block #${header.number} was authored by ${header.author}`);
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* });
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* ```
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*/
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export const subscribeNewHeads = memo((api: ApiInterfaceRx): () => Observable<HeaderExtended> => {
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return memo((): Observable<HeaderExtended> =>
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combineLatest([
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api.rpc.chain.subscribeNewHeads(),
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api.query.session.validators<Vec<AccountId>>()
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]).pipe(
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map(([header, validators]): HeaderExtended =>
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new HeaderExtended(header, validators)
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),
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drr()
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));
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}, true);
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