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-rw-r--r--src/utils/event_utils.ts44
1 files changed, 44 insertions, 0 deletions
diff --git a/src/utils/event_utils.ts b/src/utils/event_utils.ts
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+import * as _ from 'lodash';
+import * as Web3 from 'web3';
+import {EventCallback, ContractEventArg, ContractEvent, ContractEventObj, ContractEventEmitter} from '../types';
+import * as BigNumber from 'bignumber.js';
+import promisify = require('es6-promisify');
+
+export const eventUtils = {
+ wrapEventEmitter(event: ContractEventObj): ContractEventEmitter {
+ const watch = (eventCallback: EventCallback) => {
+ const bignumberWrappingEventCallback = eventUtils._getBigNumberWrappingEventCallback(eventCallback);
+ event.watch(bignumberWrappingEventCallback);
+ };
+ const zeroExEvent = {
+ watch,
+ stopWatchingAsync: async () => {
+ await promisify(event.stopWatching, event)();
+ },
+ };
+ return zeroExEvent;
+ },
+ /**
+ * Wraps eventCallback function so that all the BigNumber arguments are wrapped in a newer version of BigNumber.
+ * @param eventCallback Event callback function to be wrapped
+ * @return Wrapped event callback function
+ */
+ _getBigNumberWrappingEventCallback(eventCallback: EventCallback): EventCallback {
+ const bignumberWrappingEventCallback = (err: Error, event: ContractEvent) => {
+ if (_.isNull(err)) {
+ const wrapIfBigNumber = (value: ContractEventArg): ContractEventArg => {
+ // HACK: The old version of BigNumber used by Web3@0.19.0 does not support the `isBigNumber`
+ // and checking for a BigNumber instance using `instanceof` does not work either. We therefore
+ // compare the constructor functions of the possible BigNumber instance and the BigNumber used by
+ // Web3.
+ const web3BigNumber = (Web3.prototype as any).BigNumber;
+ const isWeb3BigNumber = web3BigNumber.toString() === value.constructor.toString();
+ return isWeb3BigNumber ? new BigNumber(value) : value;
+ };
+ event.args = _.mapValues(event.args, wrapIfBigNumber);
+ }
+ eventCallback(err, event);
+ };
+ return bignumberWrappingEventCallback;
+ },
+};