sets

on Saturday, 25th of July, 2020

Dart supports many different types of collections, or data types that contain multiple values. The most common collections:

  • List (known as an array in some languages)
  • Set
  • Map

Sets

Sets are similar to lists, with two distinctions. While a List is ordered, a set is unordered. Also, the objects in a Set are unique. And that is a guarantee.

For example, if you have a Set of int objects, and you try to add 1 to the set twice, the second attempt simply won't work. It won't throw an error or fail in anyway. Instead, Dart will just realize that the 1 already exists in the set, and it'll move on.

In order to create a set, you use the set constructor function or a Set literal.

// with constructor
Set<int> specialNumbers = Set();

// set literal
Set<int> literalSpecialNumbers = {1, 4, 6};
Sets and maps have the the same syntax for their literal implementation. When you define a set literal, you must annotate the type of the variable. Otherwise, it will default to a `Map`.

Other than that, interacting with a set is similar to interacting with a List.

Set<int> specialNumbers = Set();

specialNumbers.add(3);
print(specialNumbers);

specialNumbers.add(6);
print(specialNumbers);

// won't get added!
specialNumbers.add(6);
print(specialNumbers);


// output
// => [3]
// => [3, 6]
// => [3, 6]


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