Make tokenRegistry contract instantiation lazy and clear it on provider update

1 files changed, 14 insertions, 4 deletions

diff --git a/src/contract_wrappers/token_registry_wrapper.ts b/src/contract_wrappers/token_registry_wrapper.ts
index 8dd79171e..69bad2bac 100644
--- a/src/contract_wrappers/token_registry_wrapper.ts
+++ b/src/contract_wrappers/token_registry_wrapper.ts
@@ -6,17 +6,20 @@ import {ContractWrapper} from './contract_wrapper';
 import * as TokenRegistryArtifacts from '../artifacts/TokenRegistry.json';
 
 export class TokenRegistryWrapper extends ContractWrapper {
+    private tokenRegistryContractIfExists: TokenRegistryContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
+    public invalidateContractInstance() {
+        delete this.tokenRegistryContractIfExists;
+    }
     public async getTokensAsync(): Promise<Token[]> {
-        const contractInstance = await this.instantiateContractIfExistsAsync((TokenRegistryArtifacts as any));
-        const tokenRegistryContract = contractInstance as TokenRegistryContract;
+        await this.instantiateTokenRegistryContractIfDoesntExistAsync();
 
-        const addresses = await tokenRegistryContract.getTokenAddresses.call();
+        const addresses = await this.tokenRegistryContractIfExists.getTokenAddresses.call();
         const tokenMetadataPromises: Array<Promise<TokenMetadata>> = _.map(
             addresses,
-            (address: string) => (tokenRegistryContract.getTokenMetaData.call(address)),
+            (address: string) => (this.tokenRegistryContractIfExists.getTokenMetaData.call(address)),
         );
         const tokensMetadata = await Promise.all(tokenMetadataPromises);
         const tokens = _.map(tokensMetadata, metadata => {
@@ -30,4 +33,11 @@ export class TokenRegistryWrapper extends ContractWrapper {
         });
         return tokens;
     }
+    private async instantiateTokenRegistryContractIfDoesntExistAsync() {
+        if (!_.isUndefined(this.tokenRegistryContractIfExists)) {
+            return;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((TokenRegistryArtifacts as any));
+        this.tokenRegistryContractIfExists = contractInstance as TokenRegistryContract;
+    }
 }