Transforming With map, where, and toList
Reshape lists with iterable methods.
Transforming With map, where, and toList is a free Dart Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Dart Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Reshaping Lists
Instead of looping by hand, Dart lets you transform lists with tidy iterable methods. You describe the result and Dart builds it. ✨
map Transforms Items
The map method runs a function on every item and produces a new sequence of the results, leaving the original untouched.
var nums = [1, 2, 3];
var doubled = nums.map((n) => n * 2);map Returns an Iterable
Notice map gives back an Iterable, not a List. It is lazy, so nothing computes until you actually read the values.
toList Makes It Concrete
Turn any iterable into a real list with toList. This forces the work to run and gives you a list you can index.
var result = nums.map((n) => n * 2).toList();where Filters Items
The where method keeps only items that pass your test, dropping the rest. It is your go-to filter.
var evens = nums.where((n) => n.isEven);Chain map and where
Combine steps fluently. First where filters, then map transforms, reading like a clear sentence about your data.
var out = nums.where((n) => n > 1).map((n) => n * 10);Always Finish With toList
After chaining, call toList to lock in the result. Forget it and you keep a lazy iterable that recomputes each time.
var finalList = out.toList();Originals Stay Safe
These methods never change the source list; they return fresh data. Your original nums is exactly as it started.
print(nums); // [1, 2, 3]Change the Type
map can switch types entirely. Here a list of numbers becomes a list of String labels in one clean step.
var labels = nums.map((n) => 'item $n').toList();expand to Flatten
Use expand when each item turns into several. It maps then flattens the pieces into one smooth sequence.
var pairs = nums.expand((n) => [n, n]).toList();Quick Conversions
Other handy finishers include join to glue items into one string, perfect for showing a list to a user.
print(nums.join(', ')); // 1, 2, 3Quick Check
You chain map over a list but never call toList. What do you get?
Recap
You transformed lists like a pro: map to change items, where to filter, and toList to finalize. Pipelines beat manual loops every time. 🚀
Frequently asked questions
Is the “Transforming With map, where, and toList” lesson free?
Yes — the full text of “Transforming With map, where, and toList” is free to read here on the web, and the Dart Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Dart Academy course, upgrade to CoddyKit PRO.
What will I learn in “Transforming With map, where, and toList”?
Reshape lists with iterable methods. You practise Dart Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Dart Academy?
No prior experience is required. Dart Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Transforming With map, where, and toList” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Dart Academy lesson?
Yes. Every Dart Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Creating Lists and Indexing
- Adding, Removing, and Updating Items
- Searching and Sorting Lists
- Transforming With map, where, and toList