What is the difference between a “set” and an “array” in Swift?

In Swift, an array and a set are both collection types used to store multiple values of the same type. However, there are several important differences between them:


  • A set can only contain unique values, while an array can contain duplicate values.
  • So to say, set elements cannot be repeated.


  • A set does not maintain any specific order of its elements, while an array does.
  • This means that elements in a set can be accessed randomly, while elements in an array can be accessed sequentially by index.


  • Sets are generally faster than arrays when it comes to checking whether a specific item is contained within them due to their use of hash values.
  • In cases where you only need to check whether an element is contained, sets can be much more efficient.

When to use arrays?

You should use an array when you need to maintain the order of elements and you want to be able to access them by index quickly. Additionally, when your data needs to hold duplicate items.

When to use sets?

You should use a set when you want to ensure that elements are unique and order is not important. Additionally, when you need to quickly check if an element is already in the set.

Overall, the choice between using an array and a set depends on the specific use case of your program. If order and duplicates matter, use an array. If you need to ensure uniqueness or prioritize faster access, use a set.

How to create empty or populated sets in Swift

To create an empty set in Swift, you can use the following syntax:

var mySet = Set<Int>()
  • This creates an empty set of integer type.
  • You can replace “Int” with any other type.

To create a populated set in Swift, you can use the following syntax:

var mySet: Set<String> = ["apple", "banana", "orange"]
  • This creates a set of string type with the values “apple”, “banana”, and “orange”.
  • Note that the type of the set elements has to be specified in angled brackets after the word “Set”.

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