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Destructuring Feature in Dart 3

Posted on:June 11, 2023 at 04:00 AM


Dart is a modern, object-oriented programming language developed by Google. Originally designed as a replacement for JavaScript in web development, Dart has evolved to become a versatile language used for mobile, desktop, and server-side applications. One of the latest features added to Dart 3 is destructuring, a powerful syntax that allows developers to extract values from collections such as lists, maps and records concisely and readably. In this article, we will explore this feature in Dart and how it can simplify your code by reducing the amount of boilerplate required for common operations. We will also discuss how destructuring can be used to improve the readability of your code and provide examples of how to use it in different contexts.

What This Feature Solves And How it Can Be Beneficial For Me as a Developer

In order to answer this question let’s take the following code declaration snippet:

final keyPair = <String>["public key example", "private key example"]

as you propably already know, This key pair of a public and a private key combined as elements of a list, this is just an example and could be anything for specific use-cases such as email/password, and latitude/longitude…

Previously with Dart, in order to decouple and extract specific elements from this list we needed to do it the manual way by declaring variables and accessing items by their index in the list:

final publicKey = keyPair[0]; 
final privateKey = keyPair[1];

And so on, this code can grow to be a huge boilerplate as the list grows itself, sice we will need then to declare and access each item separately, right? which is a time-consuming and not efficient way to do it.

in the following section, we will discover what is destructuring and how it can fix this issue to provide a very helpful and developer-friendly way to get things done quickly.

What is Destructuring in Dart 3?

The destructuring feature is not a new thing across other programming languages, it is already contained in other languages such as Kotlin, Javascript… and the concept behind this feature is to extract fields from a collection or a record directly to declared variables. Now by taking the previous example, with Dart 3, in order to extract the first and second items in the keyPair variable, we can simply do:

final [publicKey, privateKey] = keyPair;

see, as simple as that. we can then expect that the publicKey will hold the first item value and the privateKey will hold the second one, here we will try to print them in the console:

print(publicKey);  // public key example
print(privateKey); // private key example

You can do the same for a Map as example

final exampleMap = {"first": 1, "second": 2};
final {"first": first, "second": second} = exampleMap;

print("$first, $second"); // 1, 2

This gives you more flexibility in your code, decreasing the required time to code, refactor, and fix. In addition that makes your code more readable and clear to analyze.

As Dart 3 came with also another new feature which called records, you can think of a record as a holder for multiple arguments that you can use directly without the need of declaring a seprated class for your fields, here is a record example:

final myRecordExample = (field1, field2, field3); 

well, working with them, you can apply the concept of destructuring a record fields directly in the same way you can do for a list as example:

var  (first, second) = exampleRecord();
print("$first, $second"); // 1, 2

// This returns a record.
(int, int) exampleRecord() {
    return (1, 2);

This feature can be even more handy with records, for example, when having an existent record, we can simply rotate/flip its field like this:

var (a, b) = (1, 2);
print("$a, $b"); // 1, 2

(b, a) = (a, b);
print("$a, $b"); // 2, 1


Dart 3 came with many interesting new features that will take your coding process to the next level, especially when you work with the Flutter framework. The destructuring feature is only one of them and It is recommended that to check other new features as well.