Data types (uint, int, bool, address, string) in Blockchain / Solidity - Mini Project: Build & Apply

Understanding Basic Blockchain Data Types

📖 Scenario: You are creating a simple smart contract to store and display different types of data commonly used in blockchain development.

🎯 Goal: Build a smart contract that declares variables of types uint, int, bool, address, and string, assigns values to them, and then outputs these values.

📋 What You'll Learn

Declare a uint variable named myUint with value 100

Declare an int variable named myInt with value -50

Declare a bool variable named myBool with value true

Declare an address variable named myAddress with value 0x1234567890123456789012345678901234567890

Declare a string variable named myString with value "Hello Blockchain"

Create a function getData that returns all these variables

💡 Why This Matters

🌍 Real World

Smart contracts use these basic data types to store and manage blockchain data like balances, flags, addresses, and messages.

💼 Career

Understanding these data types is essential for blockchain developers to write secure and efficient smart contracts.

1

Declare basic data type variables

Declare a uint variable called myUint and set it to 100. Declare an int variable called myInt and set it to -50 inside a Solidity contract named DataTypesDemo.

Blockchain / Solidity

contract DataTypesDemo {
    // Declare myUint and myInt variables here
    
}

Need a hint?

Use uint for positive numbers and int for numbers that can be negative.

2

Add bool, address, and string variables

Inside the DataTypesDemo contract, declare a bool variable called myBool set to true, an address variable called myAddress set to 0x1234567890123456789012345678901234567890, and a string variable called myString set to "Hello Blockchain".

Blockchain / Solidity

contract DataTypesDemo {
    uint myUint = 100;
    int myInt = -50;
    // Declare myBool, myAddress, and myString variables here
}

Need a hint?

Remember to use double quotes for strings and the exact address format for address.

3

Create a function to return all variables

Add a public view function called getData inside DataTypesDemo that returns myUint, myInt, myBool, myAddress, and myString in that order.

Blockchain / Solidity

contract DataTypesDemo {
    uint myUint = 100;
    int myInt = -50;
    bool myBool = true;
    address myAddress = 0x1234567890123456789012345678901234567890;
    string myString = "Hello Blockchain";

    // Add getData function here
}

Need a hint?

Use public view and specify the return types in the function signature.

4

Output the stored data

Write a simple script or test code that calls the getData function and prints the returned values in the order: myUint, myInt, myBool, myAddress, myString. For this step, just write a console.log statement inside a JavaScript test function that logs the returned tuple.

Blockchain / Solidity

contract DataTypesDemo {
    uint myUint = 100;
    int myInt = -50;
    bool myBool = true;
    address myAddress = 0x1234567890123456789012345678901234567890;
    string myString = "Hello Blockchain";

    function getData() public view returns (uint, int, bool, address, string memory) {
        return (myUint, myInt, myBool, myAddress, myString);
    }
}

// JavaScript test code
async function test() {
    const dataTypesDemo = await DataTypesDemo.deployed();
    const data = await dataTypesDemo.getData();
    // Print the data below
    
}

Need a hint?

Use console.log and convert numbers to strings if needed before printing.