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 from GJZ on Stack OverflowDifference between Array, Set and Dictionary in Swift - Stack Overflow
Swift 1.2 : What's the difference between Set and Array ?
Sets only allow unique elements in the collection.
More on reddit.comPushing values into arrays in Firestore
Array of photos - best way of accessing?
You could of course have an array of your own data structure like so:
struct Photo{
let name: String
var comments: String?
lazy var image: UIImage? = {
return UIImage(named: self.name)
}()
init(name: String){
self.name = name
}
}then you may want to initialize them more easily using an operator:
postfix operator >>{}
postfix func >> (name: String) -> Photo{
return Photo(name: name)
}then you could create a simple array out of them:
let photos = ["Photo1.png">>, "Photo2.png">>]
and then move around in the array by keeping an index into the array. If the user swipes to the left, then you increase your index and go to the end of the array and if you have already reached the end, then you can actually go to the first one if you want it to infinitely scroll.
More on reddit.comHere 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)
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.
Sets only allow unique elements in the collection.
To add to item uniqueness, let's not forget the access time. To access an element in the array, worst case scenario, when searching for an element, it takes O(n) operations (where n is size of an array), while accessing elements in set is always constant regardless of set's size - O(1).