This content originally appeared on flaviocopes.com and was authored by flaviocopes.com
This tutorial belongs to the Swift series
We use dictionaries to create a collection of key-value pairs.
Here is how to create a dictionary with 1 key-value pairs, where the key is a String and the value is an Int:
var dict = ["Roger": 8, "Syd": 7]In this case the type is inferred. You can also explicitly set the type at declaration time:
var dict: [String: Int] = ["Roger": 8, "Syd": 7]In this example we create an empty dictionary of Int keys and String values:
var dict = [String: Int]()
//or
var dict: [String: Int] = [:]You can access the value assigned to a key using this syntax:
var dict = ["Roger": 8, "Syd": 7]
dict["Roger"] //8
dict["Syd"] //7You can change the value assigned to a key in this way:
dict["Roger"] = 9A dictionary must be declared as
varto be modified. If it’s declared withlet, you cannot modify it by adding or removing elements.
Use the same syntax to add a new key/value pair:
dict["Tina"] = 4To remove a key/value paid, assign the value to nil:
dict["Tina"] = nilOr call the removeValue(forKey:) method:
dict.removeValue(forKey: "Tina")To get the number of items in the dictionary, use the count property:
var dict = ["Roger": 8, "Syd": 7]
dict.count //2If a dictionary is empty, its isEmpty property is true.
var dict = [String: Int]()
dict.isEmpty //trueThere are a lot of methods related to dictionaries, but those are the basic ones.
Dictionaries are passed by value, which means if you pass an array to a function, or return it from a function, the dictionary is copied.
Dictionaries are collections, and they can be iterated over in loops.
This content originally appeared on flaviocopes.com and was authored by flaviocopes.com
flaviocopes.com | Sciencx (2021-06-05T05:00:00+00:00) Swift Dictionaries. Retrieved from https://www.scien.cx/2021/06/05/swift-dictionaries/
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