Chapter 05: Let’s Learn Swift Programming Language – Dictionary in Swift

What is Dictionary?

 
Dictionary is unordered List which can be quickly access by key

 
Here is how you can declare Empty Dictionary

var emptyDictionary = [String : Int]()

 
Dictionary with Predefined Key Pairs

var apps = ["Productivity" : "Keynote", "Social" : "Facebook", "Music" : "iTunes"]

 
Accessing First Key Element of Dictionary

var optionalApp = apps["Productivity"] // Keynote

if var actualApp = optionalApp {
    print(actualApp) // this will get printed as there is key pair with productivity app inside apps dictionary
} else {
    print("Data Unavailable!")
}

 
If you want to access some key that doesn’t exist in dictionary

var optionalDeveloper = apps["Developer"]

if var actualDeveloper = optionalDeveloper {
    print(actualDeveloper)
} else {
    print("Data Unavailable!") // This will get printed as developer value doesn’t exist in appStore
}

 
Here is how you can add Key Pair Value to existing Dictionary

apps["Developer"] = "Xcode"

 
Here is how you can deleting Key Pair Value from existing Dictionary

apps["Social"] = nil

 
I hope this blog post will clear your doubt about Dictionary in Swift Programming Language,

 
Thanks & Regards
Mandar Apte