Expanding the Swift Knowledge Base
If you’re looking for Swift tips and tricks, the best is getting better.
I've just added 270 articles to my Swift Knowledge Base, taking it up to 576 tips, techniques, and answers for Swift developers – all updated for the latest version of Xcode and Swift. Click here to browse the knowledge base by category or search for something specific.
Many people have never heard of my work on this knowledge base, mostly because I'm terrible at marketing. If you find something useful here, please help pass on the word by telling others!
I've included a full list of all 270 new articles below, but here are my top twelve you should check out:
- How to send notifications asynchronously using NotificationQueue
- How to use an image for your background color with UIColor(patternImage:)
- How to add a custom initializer to a struct without losing its memberwise initializer
- How to lock Interface Builder controls to stop accidental changes
- How to generate shaped random numbers using GKGaussianDistribution
- How to find an aspect fit image’s size inside an image view
- How to group arrays using dictionaries
- How to read the battery level of an iPhone or iPad
- How to check whether a date is inside a date range
- How to display different strings based on available space using variantFittingPresentationWidth()
- How to preview files using Quick Look and QLPreviewController
- How to do conditional test tear down using addTeardownBlock()
If you were curious, the one that took the most time to write was "What is a monad?" – I wrote that in just a few minutes, then rewrote it, rewrote it again, then again, then again and again, until my brain was starting to switch off. It's one thing to understand something, but quite another to be able to explain it in terms that everyone can understand.
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The full list of new articles…
- How to send notifications asynchronously using NotificationQueue
- How to make optional protocol methods
- What’s the difference between frame and bounds?
- What’s the difference between init?() and init()?
- What’s the difference between == and ===?
- How to use an image for your background color with UIColor(patternImage:)
- What is a segue?
- How to stop your UISearchController bar hiding when you scroll
- How to add a custom initializer to a struct without losing its memberwise initializer
- How to restrict a protocol to classes
- How to compare dates
- How to check whether a date is inside a date range
- How to check whether users have enabled the reduced motion setting
- What is the @objc attribute?
- What is the @objcMembers attribute?
- What is a singleton?
- How to use view controller containment
- How to convert speech to text using SFSpeechRecognizer
- How to lock Interface Builder controls to stop accidental changes
- How to search your app’s Spotlight index
- How to animate a blur effect using UIVisualEffectView
- How to convert a String to Data
- How to convert Data to a String
- How to count element frequencies in an array
- What’s the difference between a static variable and a class variable?
- How to use local variable observers
- What is MVC?
- How to use reflection to inspect type data
- How to detect when the user takes a screenshot
- How to force a UIView to redraw: setNeedsDisplay()
- How to throw errors using strings
- How to make a background image run under the safe area
- How to read names in a string using NSLinguisticTagger
- How to control a UIProgressView’s animation
- How to position a view using Auto Layout anchors
- How to resize a custom font using UIFontMetrics
- What are breakpoints?
- How to render an NSAttributedString to a PDF
- How to make a UIView fade out
- How to change a view’s anchor point without moving it
- How to scan NFC tags using Core NFC
- What are watchpoints?
- How to add drag and drop to your app
- How to display PDFs using PDFView
- How to find the first matching element in an array
- How to sum an array of numbers using reduce()
- How to check whether a string contains any words from an array
- How to extract text from a PDF using PDFKit
- What is MVVM?
- How to watermark PDFs inside a PDFView
- What is a protocol associated type?
- How to use map() to transform an array
- How to use flatMap() to transform an array
- How to remove items from an array using filter()
- How to use reduce() to condense an array into a single value
- How to use map() with an optional value
- How to use flatMap() with an optional value
- What are sets?
- When to use a set rather than an array
- How to force a crash using fatalError()
- How to append one array to another array
- How to calculate the ROT13 of a string
- How to loop over non-nil items in an array
- How to find the path to a file in your bundle
- How to make a sprite follow a path
- How to generate fair random numbers using GKShuffledDistribution
- How to generate shaped random numbers using GKGaussianDistribution
- What are generics?
- What is a nested class or nested struct?
- How to reverse sort an array
- What is function composition?
- How to create a custom debug description
- How to remove the first or last item from an array
- How to use the forEach method to loop over an array
- How to make a custom sequence
- How to find the highest value in an array
- How to swap two items in an array using swapAt()
- How to use the rethrows keyword
- What is a throwing function?
- How to filter a loop using a where clause
- What is a lazy sequence?
- What is destructuring?
- How to break out of multiple loop levels using labeled statements
- How to add Markdown comments to your code
- How to create an array by repeating an item
- How to add associated values to enums
- How to add raw values to enums
- How to transform a dictionary using mapValues()
- How to read a single character from a string
- What is the Never return type?
- How to read the interface orientation: portrait or landscape?
- How to check whether an iPhone or iPad is upside down or face up
- How to use vector images in your asset catalog
- When is it safe to force unwrap optionals?
- Measuring execution speed using CFAbsoluteTimeGetCurrent()
- How to group arrays using dictionaries
- How to specify default values for dictionary keys
- How to use typealias to make it easier to use complex types
- What does the open keyword do?
- How to detect when the system is under pressure and you should reduce your work
- Why is immutability important?
- How to make a variadic function
- How to use operator overloading
- What are protocol extensions?
- What is the autoclosure attribute?
- What are static methods and variables?
- How to count matching items in an array
- Remove all instances of an object from an array
- What are designated initializers?
- What are convenience initializers?
- How to run code when an object is destroyed
- Check whether all items in an array match a condition
- Showing dictionary definitions using UIReferenceLibraryViewController
- How to make custom types from strings using ExpressibleByStringLiteral
- How to get the lines in a string as an array
- How to remove a prefix from a string
- What’s the difference between Any and AnyObject?
- How to read the red, green, blue, and alpha color components from a UIColor
- How to control which screen edges trigger system gestures using preferredScreenEdgesDeferringSystemGestures
- How to read your app’s version from your Info.plist file
- How to make the device vibrate
- How to identify your Auto Layout constraints
- How to detect when your size class changes
- What are class and subtype existentials?
- How to conform to the Equatable protocol
- How to find the view controller responsible for a view
- How to find an aspect fit image’s size inside an image view
- How to add conditions to a breakpoint
- What is key-value observing?
- How to find the index of the first matching array element
- How to find the longest initial sequence in an array
- How to check your program state using precondition()
- How to add markers to the jump bar
- How to use one-sided ranges
- How to make UIViewPropertyAnimator scrub with a custom curve: scrubsLinearly
- How to multiply an int and a double
- How to convert a string to a safe format for URL slugs and filenames
- How to simulate gravity in a SpriteKit scene
- How to debug physics in a SpriteKit scene using showsPhysics
- How to made an SKSpriteNode render faster using blendMode
- How to convert radians to degrees
- How to convert degrees to radians
- How to pass the Fizz Buzz test
- How to create a custom OptionSet
- What are keypaths?
- How to add a button to a navigation bar using storyboards
- How to add peek and pop to a UITableView
- How to use the zip() function to join two arrays
- How to use ISO-8601 dates with JSONDecoder and Codable
- How to format JSON using Codable and pretty printing
- How to sort the keys of your JSON using Codable
- How to advance time in an SKEmitterNode using advanceSimulationTime()
- How to make Xcode play sounds while debugging
- How to read the battery level of an iPhone or iPad
- What are Swift error breakpoints?
- How to specify your own date format with Codable and JSONEncoder
- How to loop audio using AVAudioPlayer and numberOfLoops
- How to hide your navigation bar when the keyboard shows: hidesBarsWhenKeyboardAppears
- How to add a number over your app icon using applicationIconBadgeNumber
- How to add a badge to your UITabBarItem
- How to run a case-insensitive search for one string inside another
- How to create keyframe animations using animateKeyframes()
- How to add a toolbar above the keyboard using inputAccessoryView
- What is the UIAppearance proxy?
- How to create a marching ants effect using lineDashPhase
- How to make a shape draw itself using strokeEnd
- How to detect long presses using UILongPressGestureRecognizer
- How to move to the next UITextField when the user presses return
- How to read the user’s location while your app is in the background
- How to download files with URLSession and downloadTask()
- How to change a sprite’s texture using SKTexture
- How to warp a sprite using SKWarpGeometryGrid
- How to crop a sprite using SKCropNode
- How to make a number positive using abs()
- How to create a project using Swift Package Manager
- What are implicitly unwrapped optionals?
- Optional vs implicitly unwrapped optional: what’s the difference?
- Self vs self – what’s the difference?
- How to make a UIView fill the screen using Auto Layout anchors
- How to mask one UIView using another UIView
- How to make your user interface in code
- How to subclass UIApplication using UIApplicationMain
- How to fix the error “protocol can only be used as a generic constraint because it has Self or associated type requirements”
- What is class inheritance?
- How to fix Auto Layout problems
- How to make one sprite draw in front of another using zPosition
- How to conform to the Comparable protocol
- How to conform to the Hashable protocol
- How to use UIPickerView
- How to write a closure that returns a value
- How to make your app open with a custom URL scheme
- How to show PDF thumbnails using PDFThumbnailView
- How to perform a segue programmatically using performSegue()
- How to make a UIView glow using shadowColor
- How to make gesture recognizers work together using require(toFail:)
- How to store NSCoding data using Codable
- What is a functor?
- What is a monad?
- What is a view’s intrinsic content size?
- How to fix the error “Expression was too complex to be solved in reasonable time”
- How to convert JSON into Swift objects using Codable
- How to take a photo using the camera and UIImagePickerController
- What is an enum?
- What is CloudKit?
- How to convert a Substring to a String
- How to remove duplicate items from an array
- How to use UIActivityIndicatorView to show a spinner when work is happening
- How to read the average color of a UIImage using CIAreaAverage
- What’s the difference between a function and a method?
- What is protocol-oriented programming?
- What is the safe area layout guide?
- How to use UISearchController to let users enter search words
- How to add scopes to a UISearchController
- How to pixellate a UIImage
- What’s the difference between a function and a closure?
- Private vs fileprivate: what’s the difference?
- How to add annotations to MKMapView using MKPointAnnotation and MKPinAnnotationView
- How to play videos using AVPlayerViewController
- How to calculate division remainder using modulo
- What is CALayer?
- How to control the sites a WKWebView can visit using WKNavigationDelegate
- How to control the user interface of a WKWebView using WKUIDelegate
- How to render PDFs using UIGraphicsPDFRenderer
- Adding places to MKMapView using MKPlacemark
- How to use UIStepper to let users change number values
- How to use multithreaded operations with OperationQueue
- How to support right-to-left languages
- How to capitalize the first letter of a string
- What is an IndexPath?
- What’s the difference between a protocol and a class?
- What is Automatic Reference Counting (ARC)?
- How to split an integer into an array of its digits
- What is a computed property?
- How to load HTTP content in WKWebView and UIWebView
- How to desaturate an image to make it black and white
- What is the first responder?
- How to load and save a struct in UserDefaults using Codable
- How to add multiple UIBarButtonItem to a navigation bar using rightBarButtonItems
- What is an escaping closure?
- How to customize a view controller’s back button on a navigation bar: backBarButtonItem
- How to round only specific corners using maskedCorners
- How to constrain a protocol associated type
- How to check whether your other apps are installed
- How to convert HTML to an NSAttributedString
- How to display different strings based on available space using variantFittingPresentationWidth()
- What is NSNumber?
- How to fix the error “View controller is unreachable because it has no entry points and no identifier for runtime access”
- What does the AppDelegate class do?
- How to concatenate strings to make one joined string
- What is typecasting?
- How to draw shapes using UIBezierPath
- How to center a view in its container
- What is the ternary operator?
- How to fix the error “Failed to instantiate the default view controller for UIMainStoryboardFile”
- What is optional chaining?
- How to check whether an integer lies inside a range
- How to split an array into chunks
- How to find the difference between two arrays
- What is an IBOutlet?
- How to preview files using Quick Look and QLPreviewController
- How to add a fragment shader to an SKSpriteNode using SKShader
- What is a UIViewController
- How to load a remote image URL into UIImageView
- How to hide the tab bar when a view controller is shown
- How to write performance tests using measure()
- How to set baselines for your performance tests
- How to test throwing functions
- How to test asynchronous functions using expectation()
- How to do one-time setup for your tests
- How to do conditional test tear down using addTeardownBlock()
SPONSORED In-app subscriptions are a pain to implement, hard to test, and full of edge cases. RevenueCat makes it straightforward and reliable so you can get back to building your app. Oh, and it's free if your app makes less than $10k/mo.
Sponsor Hacking with Swift and reach the world's largest Swift community!
About the author
Paul Hudson is the creator of Hacking with Swift, the most comprehensive series of Swift books in the world. He's also the editor of Swift Developer News, the maintainer of the Swift Knowledge Base, and a speaker at Swift events around the world. If you're curious you can learn more here.
