Lesson 3: Outline

Lesson 3 introduction and outline.

Lesson 3: Functions and Modifiers in Solidity

Objective: To understand how to write and use functions in Solidity, and to learn about function modifiers for enforcing certain conditions and managing access control in smart contracts.

Part 1: Functions in Solidity

• Function Declaration and Types:

  • Understand the syntax for declaring functions.

  • Different types of functions: public, private, internal, and external.

• Return Values and Visibility:

  • How to define return values for functions.

  • Understand the implications of function visibility.

• Function Modifiers:

  • Usage of view, pure, and state-changing functions.

• Function Parameters:

  • Passing parameters to functions.

  • Using memory and storage keywords for complex data types.

• Example: Creating a Function

  pragma solidity ^0.8.0;
  
  contract MyContract {
      uint public count = 0;
  
      function increment() public {
          count += 1;
      }
  
      function getCount() public view returns (uint) {
          return count;
      }
  }

Part 2: Modifiers in Solidity

• Understanding Modifiers:

  • Purpose of modifiers in Solidity.

  • Writing custom modifiers to enforce conditions.

• Common Use Cases:

  • Restricting access to certain functions.

  • Validating inputs or conditions before executing function logic.

• Example: Using a Modifier

  pragma solidity ^0.8.0;
  
  contract MyContract {
      address public owner;
  
      constructor() {
          owner = msg.sender;
      }
  
      modifier onlyOwner() {
          require(msg.sender == owner, "Not the owner");
          _;
      }
  
      function changeOwner(address newOwner) public onlyOwner {
          owner = newOwner;
      }
  }