Swift Learning Swift Programming Tour---collection type dictionaries (eight)

A dictionary is a memory that stores multiple data of the same type. Each value is associated with a unique key (key), which is used as the identifier for the value data in the dictionary. The data items in the dictionary are not in a specific order, unlike the data items in the array.

Dictionary writing Dictionary<key, value>. You can also write [Key:value]

Create an empty Dictionary

var namesofintegers = [int:string] ()//  namesofintegers is an empty [int:string] Dictiona Ry

Type inference writing [:]

namesofintegers["sixteen"//  namesofintegers now contains 1 Key-value pairnamesofintegers = [:]//  namesofintegers is once again an empty dictionary of Typ e [int:string]

Create dictionary literals

[Key 1:value 1, key 2:value 2, key 3:value 3]

var airports: [string:string] = ["YYZ" "Toronto Pearson"  "DUB" "Dublin"]

Type inference Writing

var airports = ["YYZ"""Toronto Pearson"" DUB " " Dublin "]

Access and modification

Count returns the key value logarithm of the dictionary

IsEmpty to determine if the dictionary is empty

　　

airports["LHR""London Heathrow

if let OldValue = Airports.updatevalue ("Dublin Airport""DUB " {    print ("Theoldvalue for DUB is \ (oldValue). ") " )}//  Prints "The old value for DUB is Dublin.

Removevalueforkey (_:) Delete key-value pairs

if let Removedvalue = Airports.removevalueforkey ("DUB") {    print ( " The removed airport ' s name is \ (removedvalue). "  Else  {    print ("Theairports Dictionary does not contain a value For DUB. " )}//  Prints "The removed airport ' s name is Dublin airport.

Traverse

 for inch Airports {    print ("\ (airportcode): \ (airportname)")}//  yyz:toronto Pearson//  Lhr:london Heathrow

 forAirportcodeinchAirports.keys {print ("Airport code: \ (Airportcode)")}//Airport Code:yyz//Airport CODE:LHR  forAirportnameinchairports.values {print ("Airport name: \ (airportname)")}//Airport Name:toronto Pearson//Airport Name:london Heathrow

Swift Learning Swift Programming Tour---collection type dictionaries (eight)