2 files changed, 18 insertions, 5 deletions
diff --git a/packages/0x.js/src/contract_wrappers/contract_wrapper.ts b/packages/0x.js/src/contract_wrappers/contract_wrapper.ts
index 873489dc9..d913e8d9b 100644
--- a/packages/0x.js/src/contract_wrappers/contract_wrapper.ts
+++ b/packages/0x.js/src/contract_wrappers/contract_wrapper.ts
@@ -32,10 +32,10 @@ const CONTRACT_NAME_TO_NOT_FOUND_ERROR: {
 
 export class ContractWrapper {
     protected _web3Wrapper: Web3Wrapper;
-    private _networkId: number;
+    protected _networkId: number;
     private _abiDecoder?: AbiDecoder;
-    private _blockAndLogStreamerIfExists: BlockAndLogStreamer | undefined;
-    private _blockAndLogStreamInterval: NodeJS.Timer;
+    private _blockAndLogStreamerIfExists?: BlockAndLogStreamer;
+    private _blockAndLogStreamIntervalIfExists?: NodeJS.Timer;
     private _filters: { [filterToken: string]: Web3.FilterObject };
     private _filterCallbacks: {
         [filterToken: string]: EventCallback<ContractEventArgs>;
@@ -162,7 +162,7 @@ export class ContractWrapper {
         );
         const catchAllLogFilter = {};
         this._blockAndLogStreamerIfExists.addLogFilter(catchAllLogFilter);
-        this._blockAndLogStreamInterval = intervalUtils.setAsyncExcludingInterval(
+        this._blockAndLogStreamIntervalIfExists = intervalUtils.setAsyncExcludingInterval(
             this._reconcileBlockAsync.bind(this),
             constants.DEFAULT_BLOCK_POLLING_INTERVAL,
             this._onReconcileBlockError.bind(this),
@@ -191,7 +191,7 @@ export class ContractWrapper {
         }
         this._blockAndLogStreamerIfExists.unsubscribeFromOnLogAdded(this._onLogAddedSubscriptionToken as string);
         this._blockAndLogStreamerIfExists.unsubscribeFromOnLogRemoved(this._onLogRemovedSubscriptionToken as string);
-        intervalUtils.clearAsyncExcludingInterval(this._blockAndLogStreamInterval);
+        intervalUtils.clearAsyncExcludingInterval(this._blockAndLogStreamIntervalIfExists as NodeJS.Timer);
         delete this._blockAndLogStreamerIfExists;
     }
     private async _reconcileBlockAsync(): Promise<void> {
diff --git a/packages/0x.js/src/contract_wrappers/ether_token_wrapper.ts b/packages/0x.js/src/contract_wrappers/ether_token_wrapper.ts
index cbafcfe94..32c9ae6a9 100644
--- a/packages/0x.js/src/contract_wrappers/ether_token_wrapper.ts
+++ b/packages/0x.js/src/contract_wrappers/ether_token_wrapper.ts
@@ -162,6 +162,19 @@ export class EtherTokenWrapper extends ContractWrapper {
     public _unsubscribeAll(): void {
         super._unsubscribeAll();
     }
+    /**
+     * Retrieves the Ethereum address of the EtherToken contract deployed on the network
+     * that the user-passed web3 provider is connected to. If it's not Kovan, Ropsten, Rinkeby, Mainnet or TestRPC
+     * (networkId: 50), it will return undefined (e.g a private network).
+     * @returns The Ethereum address of the EtherToken contract or undefined.
+     */
+    public getContractAddressIfExists(): string | undefined {
+        const networkSpecificArtifact = artifacts.EtherTokenArtifact.networks[this._networkId];
+        const contractAddressIfExists = _.isUndefined(networkSpecificArtifact)
+            ? undefined
+            : networkSpecificArtifact.address;
+        return contractAddressIfExists;
+    }
     private _invalidateContractInstance(): void {
         this._unsubscribeAll();
         this._etherTokenContractsByAddress = {};