src/contract_wrappers/erc20_wrapper.ts


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import * as _ from 'lodash';
import * as BigNumber from 'bignumber.js';
import {Web3Wrapper} from '../web3_wrapper';
import {assert} from '../utils/assert';
import {ContractWrapper} from './contract_wrapper';
import * as TokenArtifacts from '../artifacts/Token.json';
import {ERC20Contract} from '../types';

export class ERC20Wrapper extends ContractWrapper {
    constructor(web3Wrapper: Web3Wrapper) {
        super(web3Wrapper);
    }
    /**
     * Returns an owner's ERC20 token balance
     */
    public async getBalanceAsync(tokenAddress: string, ownerAddress: string): Promise<BigNumber.BigNumber> {
        assert.isETHAddressHex('ownerAddress', ownerAddress);
        assert.isETHAddressHex('tokenAddress', tokenAddress);

        const contractInstance = await this.instantiateContractIfExistsAsync((TokenArtifacts as any), tokenAddress);
        const tokenContract = contractInstance as ERC20Contract;
        let balance = await tokenContract.balanceOf.call(ownerAddress);
        // The BigNumber instance returned by Web3 is of a much older version then our own, we therefore
        // should always re-instantiate the returned BigNumber after retrieval.
        balance = _.isUndefined(balance) ? new BigNumber(0) : new BigNumber(balance);
        return balance;
    }
}