Add example for calling an Ethereum smart contract from Motoko (#3885)

* Add example for calling an Ethereum smart contract from Motoko * Apply suggestions from code review Co-authored-by: Jessie Mongeon <[email protected]> --------- Co-authored-by: Jessie Mongeon <[email protected]>
dfinity · Dec 13, 2024 · 734eac6 · 734eac6
1 parent 81d0ccf
commit 734eac6
Showing 1 changed file with 59 additions and 1 deletion.
diff --git a/docs/developer-docs/multi-chain/ethereum/evm-rpc/evm-rpc-canister.mdx b/docs/developer-docs/multi-chain/ethereum/evm-rpc/evm-rpc-canister.mdx
@@ -417,7 +417,65 @@ dfx canister call evm_rpc eth_getTransactionReceipt "(variant {$RPC_SOURCE}, $RP
 <AdornedTabs groupId="languages">
 <TabItem value="motoko" label="Motoko" default>
 
-Calling an Ethereum smart contract from Motoko is possible but not yet officially supported.
+```motoko no-repl
+import EvmRpc "canister:evm_rpc";
+
+import Cycles "mo:base/ExperimentalCycles";
+import Debug "mo:base/Debug";
+
+actor {
+  public func call() : async ?Text {
+
+    // Configure RPC request
+    let services = #EthMainnet(null);
+    let config = null;
+
+    // Add cycles to next call
+    Cycles.add<system>(2000000000);
+
+    // Call an Ethereum smart contract. The smart contract's information in this example is hard coded.
+    let result = await EvmRpc.eth_call(services, config, {
+      block = null;
+      transaction = {
+        to = ?"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
+        input = ?"0x70a08231000000000000000000000000b25eA1D493B49a1DeD42aC5B1208cC618f9A9B80"; // ABI-encoded
+        accessList = null;
+        blobVersionedHashes = null;
+        blobs = null;
+        chainId = null;
+        from = null;
+        gas = null;
+        gasPrice = null;
+        maxFeePerBlobGas = null;
+        maxFeePerGas = null;
+        maxPriorityFeePerGas = null;
+        nonce = null;
+        type_ = null;
+        value = null
+      };
+    });
+
+    // Process results
+    switch result {
+      // Prints the response if each RPC provider returns a consistent, successful result
+      case (#Consistent(#Ok response)) {
+        Debug.print("Success: " # debug_show response);
+        ?response // ABI-encoded
+      };
+      // Trap is an RPC provider returns an error message consistent with the response of the other providers
+      case (#Consistent(#Err error)) {
+        Debug.trap("Error: " # debug_show error);
+        null
+      };
+      // Trap if an RPC provider returns a response inconsistent with the other providers
+      case (#Inconsistent(_results)) {
+        Debug.trap("Inconsistent results");
+        null
+      };
+    };
+  };
+};
+```
 
 </TabItem>
 <TabItem value="rust" label="Rust">