Let’s say you have the following method in objective-c When you import this in Swift, you will be importing the code as follows As you can see from the above code, you are actually importing as implicitly unwrapped optionals. This can be a problem, if you are trying to unwrap a null object. You can
One of the most common use cases when building an app is to fetch data from a server and then display it. This can achieved by multiple means. For this blog post, we would like to query three URLs and display the data, only when all the three URLs have returned in order. Callbacks are
Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input. Example 1: Input: intervals = [[1,3],[2,6],[8,10],[15,18]] Output: [[1,6],[8,10],[15,18]] Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6]. Example 2: Input: intervals = [[1,4],[4,5]] Output: [[1,5]] Explanation: Intervals [1,4]
I came across this question on stackoverflow. https://stackoverflow.com/questions/32346456/accessing-non-static-constant-in-static-function-of-swift-class Basically it asked, how we can access instance members from static functions. The answer would be no, we can’t access instance variables from static method. But this is possible using a singleton design pattern. The actual code is shown below This is how I can alter it.
Let’s consider you are trying to download a json. You have a completion handler as shown below If you look at the method declaration, you can see that it has a completion handler to it. You can use the completion handler as shown below when using the Download method. This type of code design is
When running UX tests, we are often interrupted by alerts as shown below. Whats a good way to handle this ? There are two ways you can handle these alerts. You can either use addUIInterruptionMonitor or waitForExistence APIs to handle the alerts. You can use the below diagram to determine what you should be using.
In this tutorial, I will be explaining how we can go pass data between SwiftUI and UIKit. It’s pretty straightforward to use observable and state objects when passing data between SwiftUI views. When it comes to UIKit, you cannot directly pass these objects. There is a lot more you need to do. To visualize, my
You will commonly need to iterate through similar views and display them in SwiftUI. For e.g. similar to the image shown below. Normally we would use ForEach to iterate and display them. ForEach is a structure that computes views on demand from an underlying collection of identified data. In order to make it work, you
Problem description: You are given a number. You can swap two adjacent digits, if they are both odd or even. For e.g. given (3,8), you can’t swap them. But you can swap (5,9) since they are both odd. They have the same parity. A similar problem is explained here https://www.youtube.com/watch?v=qEIGhVtZ-sg Function description: swapDigitsAndGetLargestNumber(number: String) Returns:
The explanation is here https://www.youtube.com/watch?v=3QJzHqNAEXs We use a stack here to store the values. If the previous number is greater than the current number, we will remove the previous number. Else store the number in the stack.
Notifications are a very helpful tool, when you need to send messages between two modules which are very loosely coupled. In this blog post, I will implement my own NSNotificationCenter in Swift. Let’s start with the basic data structure needed to hold a Notification. I am using a Dictionary, which contains an array to hold
You are given the root of a binary tree. A ZigZag path for a binary tree is defined as follow: Choose any node in the binary tree and a direction (right or left). If the current direction is right, move to the right child of the current node; otherwise, move to the left child. Change the direction from right
https://leetcode.com/problems/word-ladder/ This post contains the implementation for the leetcode problem shown in the link above. A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> … -> sk such that: Every adjacent pair of words differs by a single letter. Every si for 1 <= i <= k is in wordList. Note that beginWord does not need to be in wordList.
Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order. Example 1: Input: nums = [1,2,3] Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] Example 2: Input: nums = [0,1] Output: [[0,1],[1,0]] Example 3: Input: nums = [1] Output: [[1]] Constraints: 1 <= nums.length <= 6 -10 <= nums[i] <= 10 All the integers of nums are unique.
Magical Candy BagsYou have N bags of candy. The ith bag contains arr[i] pieces of candy, and each of the bags is magical!It takes you 1 minute to eat all of the pieces of candy in a bag (irrespective of how many pieces of candy are inside), and as soon as you finish, the bag
Explaining weak and strong variables is better with an example. Let’s start with two classes Driver and Car. Don’t use Playgrounds to test this code. deinit doesn’t get called in playgrounds Run the code, you should see the class getting initialized, but never getting de-initialized. Let’s dig into why this is not happening. In ViewDidLoad,
UIScrollView is a view that allows the scrolling and zooming of its contained views. UIScrollView is the superclass of several UIKit classes including UITableView and UITextView. The central notion of a UIScrollView object (or, simply, a scroll view) is that it is a view whose origin is adjustable over the content view. It clips the content to its frame, which generally
My goal in this tutorial is to create views using constraints. I will try to use it in such a way that, anyone can use these constraints to build a more complex layout. The view I would like to create is similar to a UITableViewCell. Create a view and place it at the top of
Consider you are developing a movie app which is supposed to be released in all over the world. You get a poster image from your marketing team, and you will need to display text on it as shown below. The below image is for left to right language. The text is on the right side.
Set the property as read only Add a setter to the property. Make a note of newValue. This is a predefined swift variable which holds the new value you just passed in. DidSet and WillSet. This is self explanatory Make a note of the keywords oldValue and newValue. These are predefined values in Swift to
It’s pretty easy to accomplish this animation using the ObservableObject. Let me show you how. Use the below class to display all your views one by one. Display your views DaySwiftUIView using a for loop. Let’s write the actual class which does this animation. The single line of code which animates the view is .animation(Animation
If you look at structs and classes in Swift, they seem similar, but the most fundamental difference between them is how they handle values passed to them. In general Struct is pass by value, whereas Class is pass by reference. I will explain the difference by showing an example. In the above code, I have
Method Swizzling is the ability that Objective-C Runtime gives us, to switch the implementation of an existing selector at runtime. I came across an article in NSHipster which does method swizzling. The link to the article is here https://nshipster.com/swift-objc-runtime/ For convenience or to work around a bug in a framework, or because there’s just no
The below diagram shows the pattern I have been following to make my integration easy between the various parts of my code. Dependencies: iOS 13 is the deployment target Let’s start with an Xcode Objective-C project. Let’s name the project Interoperability. Please pay careful attention to your project name. You would be using the name
In swift you could also use var arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] arr.shuffle() Both will give you similar performance when you measure it using XCTest. Here is a chart to prove it.
Let’s try writing the data structure to support the animation as shown below. Basically you need to have multiple views be able to move back and forth. I went with circular linked list since, it maintains a pointer to the next and previous nodes. I wrote the data structure using Generics, this way we are
It has to do the following: Ability to stop and start the timers on individual rows. Store the values of the rows when it goes out of display.
All of a class’s stored properties—including any properties the class inherits from its superclass—must be assigned an initial value during initialization. Swift defines two kinds of initializers for class types to help ensure all stored properties receive an initial value. These are known as designated initializers and convenience initializers. Normally you would have a single
Lets consider you have a sample JSON as shown belowhttps://gist.github.com/kmdarshan/cfa6a940268f7091faf886ed63b3b559 You can make use of Codable Library (https://developer.apple.com/documentation/swift/codable) in Swift to read and write data from a JSON. Firstly you need to map your data from the JSON onto a Struct as shown below. Once you have done that, its easy to read it using
View the code on Gist.
View the code on Gist.
The median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value and the median is the mean of the two middle values. For example, for arr = [2,3,4], the median is 3. For example, for arr = [2,3], the median is (2 + 3) / 2 = 2.5.
Largest Triple Products You’re given a list of n integers arr[0..(n-1)]. You must compute a list output[0..(n-1)] such that, for each index i (between 0 and n-1, inclusive), output[i] is equal to the product of the three largest elements out of arr[0..i] (or equal to -1 if i < 2, as arr[0..i] then includes fewer
View the code on Gist.