NEW: Start my new Ultimate Portfolio App course with a free Hacking with Swift+ trial! >>

How to use reflection to inspect type data

Swift version: 5.2

Paul Hudson    @twostraws   

Swift has a built-in Mirror struct that lets us query any kind of data in our code. It’s most commonly used to read through the list of properties that are available, but it’s also used in playgrounds to print out user-readable values inside types.

To get started, first create a custom type then an instance of that type:

struct Person {
    var name = "Taylor Swift"
    var age = 26
}

var taylor = Person()

You can now instantiate a Mirror object from taylor, like this:

var mirror = Mirror(reflecting: taylor)

That mirror isn’t a copy of taylor, a reflection of it – something you can inspect. For example, you can loop over all the properties inside taylor and print out their names and values like this:

for case let (label?, value) in mirror.children {
    print (label, value)
}
Hacking with Swift is sponsored by Fernando Olivares

SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps.

Try the book!

Sponsor Hacking with Swift and reach the world's largest Swift community!

Available from iOS 8.0

Similar solutions…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 5.0/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.