4 files changed, 28 insertions, 3 deletions

diff --git a/src/0x.js.ts b/src/0x.js.ts
index f3da005f8..3dfdfbfcd 100644
--- a/src/0x.js.ts
+++ b/src/0x.js.ts
@@ -137,6 +137,14 @@ export class ZeroEx {
         this.tokenRegistry = new TokenRegistryWrapper(this.web3Wrapper);
     }
     /**
+     * Sets a new provider for the web3 instance used by 0x.js internally and invalidates any instantiated
+     * contract instances created with the old provider.
+     */
+    public setProvider(provider: Web3.Provider) {
+        this.web3Wrapper.setProvider(provider);
+        this.exchange.invalidateExchangeContract();
+    }
+    /**
      * Signs an orderHash and returns it's elliptic curve signature
      * This method currently supports TestRPC, Geth and Parity above and below V1.6.6
      */
diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index f0f153c2b..a7abbb078 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -1,4 +1,5 @@
 import * as _ from 'lodash';
+import * as Web3 from 'web3';
 import {Web3Wrapper} from '../web3_wrapper';
 import {ECSignature, ZeroExError, ExchangeContract} from '../types';
 import {assert} from '../utils/assert';
@@ -7,9 +8,13 @@ import * as ExchangeArtifacts from '../artifacts/Exchange.json';
 import {ecSignatureSchema} from '../schemas/ec_signature_schema';
 
 export class ExchangeWrapper extends ContractWrapper {
+    private exchangeContractIfExists: ExchangeContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
+    public invalidateExchangeContract() {
+        delete this.exchangeContractIfExists;
+    }
     public async isValidSignatureAsync(dataHex: string, ecSignature: ECSignature,
                                        signerAddressHex: string): Promise<boolean> {
         assert.isHexString('dataHex', dataHex);
@@ -19,10 +24,9 @@ export class ExchangeWrapper extends ContractWrapper {
         const senderAddressIfExists = await this.web3Wrapper.getSenderAddressIfExistsAsync();
         assert.assert(!_.isUndefined(senderAddressIfExists), ZeroExError.USER_HAS_NO_ASSOCIATED_ADDRESSES);
 
-        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
-        const exchangeInstance = contractInstance as ExchangeContract;
+        await this.instantiateExchangeContractIfDoesntExistAsync();
 
-        const isValidSignature = await exchangeInstance.isValidSignature.call(
+        const isValidSignature = await this.exchangeContractIfExists.isValidSignature.call(
             signerAddressHex,
             dataHex,
             ecSignature.v,
@@ -34,4 +38,11 @@ export class ExchangeWrapper extends ContractWrapper {
         );
         return isValidSignature;
     }
+    private async instantiateExchangeContractIfDoesntExistAsync() {
+        if (!_.isUndefined(this.exchangeContractIfExists)) {
+            return;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
+        this.exchangeContractIfExists = contractInstance as ExchangeContract;
+    }
 }
diff --git a/src/types.ts b/src/types.ts
index 6fce95706..f17beafd2 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,4 +1,5 @@
 import * as _ from 'lodash';
+import * as Web3 from 'web3';
 
 // Utility function to create a K:V from a list of strings
 // Adapted from: https://basarat.gitbooks.io/typescript/content/docs/types/literal-types.html
@@ -28,6 +29,8 @@ export interface ECSignature {
 
 export interface ExchangeContract {
     isValidSignature: any;
+    currentProvider: Web3.Provider;
+    setProvider: (provider: Web3.Provider) => void;
 }
 
 export interface TokenRegistryContract {
diff --git a/src/web3_wrapper.ts b/src/web3_wrapper.ts
index a915a89e8..e65f29b56 100644
--- a/src/web3_wrapper.ts
+++ b/src/web3_wrapper.ts
@@ -9,6 +9,9 @@ export class Web3Wrapper {
         this.web3 = new Web3();
         this.web3.setProvider(web3.currentProvider);
     }
+    public setProvider(provider: Web3.Provider) {
+        this.web3.setProvider(provider);
+    }
     public isAddress(address: string): boolean {
         return this.web3.isAddress(address);
     }