Interacting with Smart Contracts - Using Truffle

Lesson Objectives

By the end of this lesson, you will be able to:

• Interact with deployd smart contracts using the Truffle IDE.
• Retrieve and store information to smart contracts using the Truffle IDE.

Overview

In the previous modules, we outlined how to write, compile, deploy, and unit test smart contracts using Truffle IDE. In this module we provide a detailed guide on how to interact with deployed smart contracts by different ways. The first way to interact with a deployed smart contract is by using Truffle IDE.

What is Truffle IDE

Truffle is one of the most popular development environment, testing framework and asset pipeline for blockchains using the Ethereum Virtual Machine (EVM).

Demo

This demo illustrates how to interact with a smart contract that is deployed on the BNB Smart Chain using the Truffle IDE. This is a hands-on guide and readers are encourged to perform these tasks along for a better understanding. Before starting off with the practical demo, it is necessary to make sure you have the following software requisites installed. Also, make sure you have completed Module 6.2 and 6.3.

Prerequisites

• Node v16.13.0
• npm v8.1.0
• Truffle v5.5.19 (core: 5.5.19)
• MetaMask Wallet (Latest Version)

Set up

Note that to complete this guide, make sure that you have successfully written, compiled, and deployed the Hello World smart contract provided in the previous modules.

Using Truffle for Interaction with Deployed Smart Contract

• The first step is to initiate truffle develop environment by running the command truffle develop --config=truffle-config-bsc.js
• We will now be using the local development setting of truffle for deploying and interacting with our smart contract.
• In order to deploy your smart contract locally, run the command, truffle migrate
• To interact with the deployed contract, we will have to create an instance of it. Run the command let instance = await HelloWorld.deployed() to create an instance. If you type instance and press enter, it will now return the ABI of the HelloWorld smart contract, as shown in the figure below.

• Now that we have an instance, we can use it to make function calls for getting message or setting name to greet.
• To call the getMessage() function which returns the greeting message there are two ways; wither store the result returned into a variable and then print the value of that variable or directly print the value returned by the function.
  • To store value returned by the function into a variable use the statement let message = await instance.getMessage(). To print the value of the variable message type message and press enter.

• To print value returned by the function directly use the statement await instance.getMessage()

• To use the setName function, you can either
  • Use a variable, say setName and issue the function call, this will store the transaction detail into the setName variable. You can also make a direct call to function, using await instance.setName("Maryam")

• To view the greeting message and confirm that the name is changed, issue the command instance.getMessage()