Tips on ZK Punk

Interval picker in SwiftUI

Sun, 05 Feb 2023 12:03:15 +0530

Last run on Xcode 14.2, iOS 16.2, and Swift 5.7.2

Picker View for Time Durations Link to heading

In my Timer app, I needed a Picker View for taking the timer interval from the user. Sadly, at this moment SwiftUI does not come with a built in View that I needed for my use case. However, SwiftUI does provide the building blocks to create such a view.

Change Back Button Icon in Navigation Bar

Tue, 31 Jan 2023 07:27:15 +0530

Last Run on XCODE 14.2 / iOS 16.2 / Swift 5.7.2

Change the Back Button’s Icon Link to heading

If you have used the default Settings App that comes with iOS, you are most likely to be familar with the back button with the “less than” symbol “< Back” on the top left of your iOS devices screen (in the navigation bar). It’s something we have gotten very used to, thanks to it being implemented in not only the first party apps by Apple, but also the innumerous 3rd party apps that use the NavigationStack and related API’s.

Dynamic Buttons to handle different app behvaior in SwiftUI

Sat, 21 Jan 2023 12:42:15 +0530

Last Run on XCODE 14.2 / iOS 16.2 / Swift 5.7.2

Making a Dynamic Button Link to heading

If you have noticed, the play button on most media players changes to pause once the media starts playing and vice versa. This is a behavior, I also needed in one of my apps that I was building.

It’s a functionality pretty staright forward to achieive in SwiftUI.

Making a Progress View Ring

Tue, 17 Jan 2023 13:48:35 +0530

Last Run on XCODE 14.2 / iOS 16.2 / Swift 5.7.2

Progress View Ring Link to heading

I was building a Timer app and needed a visual indicator to display the the amount of time left while the countdown was running. A circular progress bar similar to the fitness/activity rings of Apple Watch made the most sense. Sadly, Apple currently doesn’t provide a good API to use such a view in your own apps. However, building such a View in SwiftUI is pretty simple.

Getting Component Information From Date

Tue, 04 Aug 2020 20:59:37 -0700

Last Run on XCODE 11.6 / Swift 5.2 Last Run on XCODE 12.0 beta 4 / Swift 5.3

Definition Link to heading

Calendar - A definition of the relationships between calendar units (such as eras, years, and weekdays) and absolute points in time, providing features for calculation and comparison of dates.

The Calendar is a value type (struct) that provides with functions that can assist us in decoupling the component information from a given date like the year, month, day of week etc.

Usage of CaseIterable in Swift Enum

Tue, 21 Jul 2020 22:04:00 -0700

Last Run on XCODE 11.6 / Swift 5.2

Definition Link to heading

CaseIterable is a protocol in Swift, that typically lets an enumeration to provide all of its cases as a collection.

Lets look at a simple example from my RoadRage car game. This is an enum type called TrafficType listing the cases of traffic/obstacle Sprites generated in my RoadRage car game.

enum TrafficType: UInt32 {
    case Police
    case Ambulance
    case FireTruck
    case Van
    case SportsCar
    case Taxi
}

In my game I would like to find out the total count of the TrafficType entities. I would also like the ability to randomly pick a traffic object from the list to keep generating obstacles during the game loop. And to achive that is as simple as conforming to the CaseIterable protocol in the enum.

Injecting custom behavior during editmode on a TextField in SwiftUI

Fri, 17 Jul 2020 08:30:06 -0700

Last Run on XCODE 11.6 / Swift 5.2

Definitions Link to heading

‘TextField’ is a View provided in SwiftUI for handling user entered input into an app. As per the documentaion, Apple defines it as

“TextField - A control that displays an editable text interface.”

struct TextFieldEditMode: View {
    @State private var someData = ""
    var body: some View {
        TextField("Type something", text: $someData)
            .font(.largeTitle)
    }
}

Initializers Link to heading

The ‘TextField’ has four initializers, and the one we will be using in this post is the one listed below, that provides us with two additional parameters “onEditingChanged” and “onCommit”.

Custom View Modifiers in SwiftUI

Wed, 15 Jul 2020 21:32:39 -0700

Last Run on XCODE 11.6 / Swift 5.2

In SwiftUI View(s) are the building blocks of the UI. All changes to the Views are done by calling special functions called modfiers that wrap up the original View with the needful changes and return a View back.

In the example below, we apply a few modifiers to a Text view to create the impression of a highlighted text.

Text("I ♥️ SwiftUI")
    .font(.largeTitle)
    .foregroundColor(.black)
    .background(Color.yellow)

User Input in Swift commandline

Sun, 03 May 2020 22:18:51 -0700

Last Run on XCODE 11.4 / Swift 5.2

If you are writing a command line tool and need user input, the readLine() function can be used for it. It returns an optional

let input = readLine()

And, if you dont want the ending new line character, you can set the strippingNewline parameter to true.

let input = readLine(strippingNewline: true)

Checking if a Swift String contains a certain text

Fri, 01 May 2020 12:11:26 -0700

Last Run on XCODE 11.4 / Swift 5.2

A simple way to check if a string contains a certain text is to use the method contains available to Strings.

In the code snippet below, we will check if a string contains a certain text.

let fruit1 = "apple"
let fruit2 = "banana"
let mySentence = "An apple a day keeps the doctor away."

mySentence.contains(fruit1) // result --> True
mySentence.contains(fruit2) // result --> False

If we need to check the string against multiple options, we will have to use a variation of the contains method that takes a closure. Checkout the code snippet below.

Matching Swift Strings by Prefix or Suffix

Tue, 28 Apr 2020 21:56:43 -0700

Last Run on XCODE 11.4 / Swift 5.2

A simple way to check if a string starts or ends with a certain pattern is to use the method hasSuffix and hasPrefix available to Strings.

In the code snippet below, we will check if a string begins or ends with a specific text pattern.

let fileName1 = "InstagramCover.jpg"
let fileName2 = "SnapchatCover.doc"

fileName1.hasSuffix("jpg") // result --> True
fileName2.hasSuffix("jpg") // result --> False

fileName1.hasPrefix("Instagram") // --> True
fileName2.hasPrefix("Facebook") // result --> False

If we need to check against multiple variations, we can’t just use hasSuffix. Instead, we will have to use it along with another method contains. Checkout the code snippet below.

Access Swift String by Index

Tue, 21 Apr 2020 22:23:31 -0700

Last Run on XCODE 11.4 / Swift 5.2

The swift string class does not provide the ability to get a character at a specific index because of its native support for UTF characters.

In the code snippets below, we will walk through code to access elements of a string at speific positions.

Getting the first Character Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the first Character
mySwiftString.first

let firstIndex = mySwiftString.startIndex
mySwiftString[firstIndex]

Getting the last Character Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the last Character
mySwiftString.last

let lastIndex = mySwiftString.index(before: mySwiftString.endIndex)
mySwiftString[lastIndex]

Getting the 2nd Character Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the 2nd Character
let secondIndex_Ver1 = mySwiftString.index(after: firstIndex)
mySwiftString[secondIndex_Ver1]

let secondIndex_Ver2 = mySwiftString.index(firstIndex, offsetBy: 1)
mySwiftString[secondIndex_Ver2]

Getting the Nth Character from start ( Say 3rd) Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the Nth Character from start ( Say 3rd )
let thirdIndex = mySwiftString.index(firstIndex, offsetBy: 2)
mySwiftString[thirdIndex]

Getting the Nth Character from end ( Say 3rd last ) Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the Nth Character from end ( Say 3rd last )
let thirdLastIndex = mySwiftString.index(lastIndex, offsetBy: -2)
mySwiftString[thirdLastIndex]

How to enumerate nodes in Spritekit?

Fri, 10 Apr 2020 09:00:05 -0700

Last Run on XCODE 11.4 / Swift 5.2

Spritekit has a method enumerateChildNodes that searches the children of the receiving node to perform processing for nodes that share a name.

In the code snippet below, we are are iterating through all the nodes with the name “trafficCar” in the parent node (or SKScene) and performing some action on it.

func moveTraffic() {
    enumerateChildNodes(withName: "trafficCar") { 
        (trafficCar, stop) in
        let car = trafficCar as! SKSpriteNode
        car.position.y -= 10
        }
    }