3 files changed, 17 insertions, 15 deletions

diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index 90b9a39d2..3f6eb0dab 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -7,11 +7,11 @@ import * as ExchangeArtifacts from '../artifacts/Exchange.json';
 import {ecSignatureSchema} from '../schemas/ec_signature_schema';
 
 export class ExchangeWrapper extends ContractWrapper {
-    private exchangeContractIfExists: ExchangeContract;
+    private exchangeContractIfExists?: ExchangeContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
-    public invalidateContractInstance() {
+    public invalidateContractInstance(): void {
         delete this.exchangeContractIfExists;
     }
     public async isValidSignatureAsync(dataHex: string, ecSignature: ECSignature,
@@ -23,9 +23,9 @@ export class ExchangeWrapper extends ContractWrapper {
         const senderAddressIfExists = await this.web3Wrapper.getSenderAddressIfExistsAsync();
         assert.assert(!_.isUndefined(senderAddressIfExists), ZeroExError.USER_HAS_NO_ASSOCIATED_ADDRESSES);
 
-        await this.instantiateExchangeContractIfDoesntExistAsync();
+        const exchangeContract = await this.getExchangeContractAsync();
 
-        const isValidSignature = await this.exchangeContractIfExists.isValidSignature.call(
+        const isValidSignature = await exchangeContract.isValidSignature.call(
             signerAddressHex,
             dataHex,
             ecSignature.v,
@@ -37,11 +37,12 @@ export class ExchangeWrapper extends ContractWrapper {
         );
         return isValidSignature;
     }
-    private async instantiateExchangeContractIfDoesntExistAsync() {
+    private async getExchangeContractAsync(): Promise<ExchangeContract> {
         if (!_.isUndefined(this.exchangeContractIfExists)) {
-            return;
+            return this.exchangeContractIfExists;
         }
         const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
         this.exchangeContractIfExists = contractInstance as ExchangeContract;
+        return this.exchangeContractIfExists;
     }
 }
diff --git a/src/contract_wrappers/token_registry_wrapper.ts b/src/contract_wrappers/token_registry_wrapper.ts
index 69bad2bac..86bea1c5d 100644
--- a/src/contract_wrappers/token_registry_wrapper.ts
+++ b/src/contract_wrappers/token_registry_wrapper.ts
@@ -6,20 +6,20 @@ import {ContractWrapper} from './contract_wrapper';
 import * as TokenRegistryArtifacts from '../artifacts/TokenRegistry.json';
 
 export class TokenRegistryWrapper extends ContractWrapper {
-    private tokenRegistryContractIfExists: TokenRegistryContract;
+    private tokenRegistryContractIfExists?: TokenRegistryContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
-    public invalidateContractInstance() {
+    public invalidateContractInstance(): void {
         delete this.tokenRegistryContractIfExists;
     }
     public async getTokensAsync(): Promise<Token[]> {
-        await this.instantiateTokenRegistryContractIfDoesntExistAsync();
+        const tokenRegistryContract = await this.getTokenRegistryContractAsync();
 
-        const addresses = await this.tokenRegistryContractIfExists.getTokenAddresses.call();
+        const addresses = await tokenRegistryContract.getTokenAddresses.call();
         const tokenMetadataPromises: Array<Promise<TokenMetadata>> = _.map(
             addresses,
-            (address: string) => (this.tokenRegistryContractIfExists.getTokenMetaData.call(address)),
+            (address: string) => (tokenRegistryContract.getTokenMetaData.call(address)),
         );
         const tokensMetadata = await Promise.all(tokenMetadataPromises);
         const tokens = _.map(tokensMetadata, metadata => {
@@ -33,11 +33,12 @@ export class TokenRegistryWrapper extends ContractWrapper {
         });
         return tokens;
     }
-    private async instantiateTokenRegistryContractIfDoesntExistAsync() {
+    private async getTokenRegistryContractAsync(): Promise<TokenRegistryContract> {
         if (!_.isUndefined(this.tokenRegistryContractIfExists)) {
-            return;
+            return this.tokenRegistryContractIfExists;
         }
         const contractInstance = await this.instantiateContractIfExistsAsync((TokenRegistryArtifacts as any));
         this.tokenRegistryContractIfExists = contractInstance as TokenRegistryContract;
+        return this.tokenRegistryContractIfExists;
     }
 }
diff --git a/test/0x.js_test.ts b/test/0x.js_test.ts
index 0c2afe879..b404b27ba 100644
--- a/test/0x.js_test.ts
+++ b/test/0x.js_test.ts
@@ -18,8 +18,8 @@ describe('ZeroEx library', () => {
             const web3 = web3Factory.create();
             const zeroEx = new ZeroEx(web3);
             // Instantiate the contract instances with the current provider
-            await (zeroEx.exchange as any).instantiateExchangeContractIfDoesntExistAsync();
-            await (zeroEx.tokenRegistry as any).instantiateTokenRegistryContractIfDoesntExistAsync();
+            await (zeroEx.exchange as any).getExchangeContractAsync();
+            await (zeroEx.tokenRegistry as any).getTokenRegistryContractAsync();
             expect((zeroEx.exchange as any).exchangeContractIfExists).to.not.be.an('undefined');
             expect((zeroEx.tokenRegistry as any).tokenRegistryContractIfExists).to.not.be.an('undefined');