Dart Comments

Types of Comments

// This is a comment

/* This is a
   multi-line comment */

/// This documents a function

// print('This won't run');

🔹 Single-line Comments

Use // to create single-line comments:

void main() {
  // This is a single-line comment
  print('Hello World');
  
  // You can add comments above code
  var name = 'John'; // Or at the end of lines
  
  // Comments can explain what the code does
  var age = 25; // Store the user's age
  
  print('Name: $name, Age: $age');
}

🔹 Multi-line Comments

Use /* */ to create comments that span multiple lines:

void main() {
  /*
   * This is a multi-line comment
   * It can span several lines
   * Useful for longer explanations
   */
  
  print('Multi-line comments are useful');
  
  /* 
  You can also write them like this
  without the asterisks
  */
  
  var result = 10 * 5; /* Inline multi-line comment */
  print('Result: $result');
}

🔹 Documentation Comments

Use /// to create documentation comments for functions and classes:

/// This function calculates the area of a rectangle
/// [width] - The width of the rectangle
/// [height] - The height of the rectangle
/// Returns the area as a double
double calculateArea(double width, double height) {
  return width * height;
}

void main() {
  /// Calculate area for a room
  var roomArea = calculateArea(10.0, 12.0);
  print('Room area: $roomArea square meters');
}

🔹 Commenting Best Practices

Follow these guidelines for effective commenting:

void main() {
  // Good: Explains the business rule
  var discountRate = 0.1; // 10% discount for new customers
  
  // Bad: States the obvious
  // var age = 25; // Set age to 25
  
  // Good: Explains complex calculation
  var tax = price * 0.08; // State sales tax rate
  
  // Good: Explains why we do something
  if (age < 18) {
    // Minors need parental consent for account creation
    requireParentalConsent();
  }
}

🔹 Commenting Out Code

Use comments to temporarily disable code during development:

void main() {
  print('This code runs');
  
  // Temporarily disabled for testing
  // print('This code is commented out');
  // var unused = 'This variable is disabled';
  
  /*
  You can also comment out multiple lines
  print('Line 1');
  print('Line 2');
  print('Line 3');
  */
  
  print('This code runs too');
}

🔹 Practical Example

A well-commented Dart program:

/// Simple calculator program
/// Demonstrates proper commenting techniques
void main() {
  // Input values for calculation
  var num1 = 15;
  var num2 = 4;
  
  /* 
   * Perform basic arithmetic operations
   * and display the results
   */
  
  // Addition
  var sum = num1 + num2;
  print('$num1 + $num2 = $sum');
  
  // Division with decimal result
  var division = num1 / num2; // Use / for decimal division
  print('$num1 ÷ $num2 = $division');
  
  // TODO: Add more operations later
  // print('More operations coming soon!');
}