Difference between Array, Set and Dictionary in Swift

Question

I am new to Swift Lang, have seen lots of tutorials, but it's not clear – my question is what's the main difference between the Array, Set and Dictionary collection type?

Answer 1

Here are the practical differences between the different types:

Arrays are effectively ordered lists and are used to store lists of information in cases where order is important.

For example, posts in a social network app being displayed in a tableView may be stored in an array.

Sets are different in the sense that order does not matter and these will be used in cases where order does not matter.

Sets are especially useful when you need to ensure that an item only appears once in the set.

Dictionaries are used to store key, value pairs and are used when you want to easily find a value using a key, just like in a dictionary.

For example, you could store a list of items and links to more information about these items in a dictionary.

Hope this helps :)

(For more information and to find Apple's own definitions, check out Apple's guides at https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html)

Answer 2

Detailed documentation can be found here on Apple's guide. Below are some quick definations extracted from there:

Array

An array stores values of the same type in an ordered list. The same value can appear in an array multiple times at different positions.

Set

A set stores distinct values of the same type in a collection with no defined ordering. You can use a set instead of an array when the order of items is not important, or when you need to ensure that an item only appears once.

Dictionary

A dictionary stores associations between keys of the same type and values of the same type in a collection with no defined ordering. Each value is associated with a unique key, which acts as an identifier for that value within the dictionary. Unlike items in an array, items in a dictionary do not have a specified order. You use a dictionary when you need to look up values based on their identifier, in much the same way that a real-world dictionary is used to look up the definition for a particular word.