72 lines
1.7 KiB
Markdown
72 lines
1.7 KiB
Markdown
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@polkadot/rpc-core
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==================
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This library provides a clean wrapper around all the methods exposed by a Polkadot network client.
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Usage
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-----
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Installation -
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```
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yarn add @polkadot/rpc-core
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```
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Initialisation -
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```js
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import Rpc from '@polkadot/rpc-core';
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import WsProvider from '@polkadot/rpc-provider/ws';
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const provider = new WsProvider('http://127.0.0.1:9944');
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const api = new Rpc(provider);
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```
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Retrieving the block header object for a given block header hash (a 0x-prefixed hex string with length of 64) -
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```js
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api.chain
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.getHeader('0x1234567890')
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.then((header) => console.log(header))
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.catch((error) => console.error(error));
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```
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Retrieving the best block number, parent hash, state root hash, extrinsics root hash, and digest (once-off) -
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```js
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api.chain
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.getHead()
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.then((headerHash) => {
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return api.chain.getHeader(headerHash);
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})
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.then((header) => {
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console.log(`best #${header.blockNumber.toString()}`);
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console.log(`parentHash: ${header.parentHash.toString()}`);
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console.log(`stateRoot: ${header.stateRoot.toString()}`);
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console.log(`extrinsicsRoot: ${header.extrinsicsRoot.toString()}`);
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console.log(`digest: ${header.digest.toString()}`);
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})
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.catch((error) => {
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console.error('error:', error);
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});
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```
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Retrieving best header via subscription -
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```js
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api.chain
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.subscribeNewHead((header) => {
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console.log(`best #${header.blockNumber}`);
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})
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.then((subscriptionId) => {
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console.log(`subscriptionId: ${subscriptionId}`);
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// id for the subscription, can unsubscribe via
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// api.chain.subscribeNewHead.unsubscribe(subscriptionId);
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})
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.catch((error) => {
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console.error('error subscribing:', error);
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});
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```
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