Control Flow in Solidity

This example demonstrates if/else conditions, ternary operators, and loops in Solidity.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract ControlFlow {
    // State variables
    uint256[] public numbers;

    // If/else example with ternary operator
    function checkValue(uint256 _value) public pure returns (string memory) {
        // Traditional if/else
        if (_value > 100) {
            return "Greater than 100";
        } else if (_value == 100) {
            return "Equal to 100";
        } else {
            return "Less than 100";
        }
    }

    // Ternary operator example
    function isEven(uint256 _number) public pure returns (string memory) {
        // Ternary operator: condition ? value if true : value if false
        return _number % 2 == 0 ? "Even" : "Odd";
    }

    // For loop example
    function sumArray() public view returns (uint256) {
        uint256 sum = 0;

        for(uint256 i = 0; i < numbers.length; i++) {
            sum += numbers[i];
        }

        return sum;
    }

    // While loop example (with break and continue)
    function findFirstMultipleOf(uint256 _number) public view returns (uint256) {
        uint256 i = 0;

        while(i < numbers.length) {
            // Skip if number is 0
            if(numbers[i] == 0) {
                i++;
                continue;
            }

            // Found a multiple
            if(numbers[i] % _number == 0) {
                break;
            }

            i++;
        }

        return i < numbers.length ? numbers[i] : 0;
    }

    // Function to add numbers for testing
    function addNumber(uint256 _number) public {
        numbers.push(_number);
    }
}

Key Concepts

1. If/Else Conditions

   • Traditional if/else blocks
   • Multiple conditions with else if
   • Nested conditions possible

2. Ternary Operator

   • Shorthand for simple if/else
   • Format: condition ? value if true : value if false
   • More gas efficient for simple conditions

3. Loops

   • For loops with standard syntax
   • While loops for conditional iteration
   • Break and continue statements
   • Gas considerations with loops

Best Practices

1. Use ternary operators for simple conditions
2. Be careful with loops over unbounded arrays
3. Consider gas costs when using loops
4. Use break and continue appropriately
5. Always consider edge cases in conditions