Add getExchangeInstanceOrThrowAsync && getSenderAddressOrThrowAsync

src/contract_wrappers/exchange_wrapper.ts

@@ -16,11 +16,8 @@ export class ExchangeWrapper extends ContractWrapper {
         assert.doesConformToSchema('ecSignature', ecSignature, ecSignatureSchema);
         assert.isETHAddressHex('signerAddressHex', signerAddressHex);
 
-        const senderAddressIfExists = await this.web3Wrapper.getSenderAddressIfExistsAsync();
+        const senderAddress = await this.web3Wrapper.getSenderAddressOrThrowAsync();
-        assert.assert(!_.isUndefined(senderAddressIfExists), ZeroExError.USER_HAS_NO_ASSOCIATED_ADDRESSES);
+        const exchangeInstance = await this.getExchangeInstanceOrThrowAsync();
-
-        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
-        const exchangeInstance = contractInstance as ExchangeContract;
 
         const isValidSignature = await exchangeInstance.isValidSignature.call(
             signerAddressHex,
@@ -29,9 +26,13 @@ export class ExchangeWrapper extends ContractWrapper {
             ecSignature.r,
             ecSignature.s,
             {
-                from: senderAddressIfExists,
+                from: senderAddress,
             },
         );
         return isValidSignature;
     }
+    private async getExchangeInstanceOrThrowAsync(): Promise<ExchangeContract> {
+        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
+        return contractInstance as ExchangeContract;
+    }
 }

src/web3_wrapper.ts

@@ -2,6 +2,8 @@ import * as _ from 'lodash';
 import * as Web3 from 'web3';
 import * as BigNumber from 'bignumber.js';
 import promisify = require('es6-promisify');
+import {ZeroExError} from "./types";
+import {assert} from "./utils/assert";
 
 export class Web3Wrapper {
     private web3: Web3;
@@ -20,6 +22,11 @@ export class Web3Wrapper {
         const firstAccount = await this.getFirstAddressIfExistsAsync();
         return firstAccount;
     }
+    public async getSenderAddressOrThrowAsync(): Promise<string> {
+        const senderAddressIfExists = await this.getSenderAddressIfExistsAsync();
+        assert.assert(!_.isUndefined(senderAddressIfExists), ZeroExError.USER_HAS_NO_ASSOCIATED_ADDRESSES);
+        return senderAddressIfExists as string;
+    }
     public async getFirstAddressIfExistsAsync(): Promise<string|undefined> {
         const addresses = await promisify(this.web3.eth.getAccounts)();
         if (_.isEmpty(addresses)) {