**Course Title:** Mastering Dart: From Fundamentals to Flutter Development **Section Title:** Working with Collections and Generics **Topic:** Introduction to the Iterable class and collection methods **Introduction** In the previous topics, we explored the basics of working with collections in Dart, including lists, sets, and maps. We also learned about generics and how they can help us create type-safe collections. In this topic, we'll dive deeper into the world of collections and explore the Iterable class and its various methods. **What is the Iterable class?** The Iterable class is a fundamental class in the Dart standard library that represents a collection of objects that can be iterated over. It provides a common interface for various collections, including lists, sets, and maps. The Iterable class is the base class for all collections in Dart, and it provides a set of methods that can be used to iterate over the elements of a collection. **Iterable Methods** The Iterable class provides a range of methods that can be used to iterate over the elements of a collection. Some of the most commonly used methods include: * `iterator`: Returns an iterator that can be used to iterate over the elements of the collection. * `forEach`: Calls a callback function for each element in the collection. * `map`: Returns a new iterable that contains the results of applying a transformation function to each element in the collection. * `where`: Returns a new iterable that contains only the elements that match a given predicate. * `any`: Returns true if any element in the collection matches a given predicate. * `every`: Returns true if all elements in the collection match a given predicate. * `reduce`: Reduces the elements of the collection to a single value by applying a reduction function. **Example Code** ```dart void main() { // Create a list of integers List<int> numbers = [1, 2, 3, 4, 5]; // Use the forEach method to print each number numbers.forEach((number) { print(number); }); // Use the map method to double each number List<int> doubleNumbers = numbers.map((number) => number * 2).toList(); print(doubleNumbers); // [2, 4, 6, 8, 10] // Use the where method to filter out even numbers List<int> oddNumbers = numbers.where((number) => number % 2 == 1).toList(); print(oddNumbers); // [1, 3, 5] // Use the any method to check if any number is greater than 3 bool hasLargeNumber = numbers.any((number) => number > 3); print(hasLargeNumber); // true // Use the every method to check if all numbers are greater than 0 bool allPositive = numbers.every((number) => number > 0); print(allPositive); // true // Use the reduce method to sum up all numbers int sum = numbers.reduce((a, b) => a + b); print(sum); // 15 } ``` **Key Concepts** * The Iterable class is the base class for all collections in Dart. * The Iterable class provides a set of methods that can be used to iterate over the elements of a collection. * The forEach method calls a callback function for each element in the collection. * The map method returns a new iterable that contains the results of applying a transformation function to each element in the collection. * The where method returns a new iterable that contains only the elements that match a given predicate. **Practical Takeaways** * Use the Iterable class to iterate over the elements of a collection. * Use the forEach method to perform an action on each element in a collection. * Use the map method to transform the elements of a collection. * Use the where method to filter out elements of a collection based on a predicate. **External Resources** * [Iterable class documentation](https://api.dart.dev/stable/2.18.2/dart-core/Iterable-class.html) * [Dart collections tutorial](https://dart.dev/guides/libraries/library-tour#collections) **Leave a comment or ask for help** If you have any questions or need further clarification on any of the concepts covered in this topic, please leave a comment below.