When the user taps an on App icon, iOS creates an instance of UIApplication which runs on the main thread. This main thread processes all UI events such as touch, location updates etc.
After app launched successfully, it becomes available for the user to do interactions with it and every single interaction which known as an event is processed in a FIFO manner.
Now while events are being processed there may come some UI update requests which aren’t get fulfilled immediately. Instead, the system waits until the existing process finishes and the next redraw cycle comes. There is a periodic interval between the event processing and UI layout handling. The setLayoutNeeded() and layoutIfNeeded are two UIView’s methods here to ask the system for updating the view with new changes.
The setNeedsLayout() tells the system that you want the view and all it’s subviews to be redrawn in the update cycle.
Here is What Apple’s doc says on this, “Call this method on your application main thread when you want to adjust the layout of a view’s subviews. Note that it returns immediately (Async call) because it does not force an update, it waits for the next update cycle”.
Whereas layoutIfNeeded() is an async call which tells the system that you want the view and it’s subviews to be redrawn immediately without waiting for the next update cycle.
UIView have one more method named layoutSubviews() which you can use for your own implementation to set the frame of your view directly by overriding it. And since it’s default implementation uses the constraints you have given to determine it’s size and positions to get the frame, you should override it unless autoresizing and constraint behavior is not working for you as expected.
In short use setNeedsLayout(), if you are okay with the system to update it in the next upcoming update cycle and use layoutIfNeeded() if you want it to be updated immediately.
Thanks for reading.
Announced in 2014, the Swift programming language has quickly become one of the fastest growing languages in history. Swift makes it easy to write software that is incredibly fast and safe by design.
Blog for developers to highlight, top 10 trending open source to learn.
- MessageViewController A SlackViewController replacement written in Swift, compatible with iPhone X, iOS12. Created by Ryan Nystrom
- Swift interpreter for Pascal language (Inspired from Ruslan’s Blog). Created by Igor Kulman
- CollectionViewSlantedLayout subclass of the UICollectionViewLayout allowing the display of slanted cells in a UICollectionView.Created by Yassir Barchi
- Mint Package manager that installs and runs Swift command line tools, created by Yonas Kolb
- CryptoSwift Collection of standard and secure cryptographic algorithms implemented in Swift. Created by Marcin Krzyzanowski
- CocoaDebug Debugger tools for iOS supports Swift and Objective C, created by CocoaDebug
- iOS-Depth-Sampler Examples of Depth APIs in iOS, created by Shuichi Tsutsumi
- Universal Link Testing It fetches and parses apple-app-site-association file for you to quickly check whether Universal Links are working. created by Ethan Huang
- Swift Syntax Set of Swift bindings for the libSyntax library. It allows for Swift tools to parse, inspect, generate, and transform Swift source code. Created by Apple
- WhatsNewKit Showcase your awesome new app features, Created by Sven Tiigi
Thanks for reading!
The table of two values, Behaviour and Structure!
Is it more important for the software system to work or is it more important to be easy to change? If you ask the business managers they will say work is more important, some developers also go along with this attitude but that’s the wrong attitude.
Why the wrong attitude?
- If you give me a program that works perfectly but impossible to change, it means it won’t work when the requirements change.
- If you give me a program that does not work but easy to change, it means I can make the change to make it work.
If you’re a programmer with the attitude (1.) then one day your system will reach to the point where the change will be impractical (cost of change will be unaffordably high).
Eisenhower said, I have two kinds of problems, the urgent and the important, where the urgent are not important and the important is never urgent.
when it comes to software, The first value of software is behavior, is urgent but not always important. The second value is architecture, is important but never urgent. Of course, some things are not urgent and not important.
- Urgent and important
- Not urgent and important
- Urgent and not important
- Not urgent and not important.
Mistakes that business managers and developer make is to elevate items in position 3 to 1. It means they always fail to separate those features that are urgent but not important from those features that are really urgent and important and this failure leads to ignoring the important architecture of the system in favor of the unimportant features of the system.
So if you are a software developer, you are hired to maintain the quality and structure of the system and only you know the importance of the architecture.
Thanks for reading it, if you want to read in more detail, buy “Clean Architecture by Robert C. Martin”
What are the Design and Architecture?
The design is more often seems to when it comes to structures and low-level decisions whereas Architecture is often used in the context of something at the high level where we can see how components are connected with each other. But for starters, there is no different at all.
What is the GOAL of good software design?
The goal of software architecture is to minimize the Human Resources required to build and maintain the required system (By Uncle Bob Martin)
Basic fundamentals measure the design?
The measure of design quality is simply the measure of the effort required to meet the needs of the customer if the effort is low and stays same through the lifetime, System design is good else it’s bad.
The Signature of a system design mess?
- Developer point of view
The graph says developers started with nearly 100% of productivity but with each release, their productivity going down
- Executive point of view?
Release 1 was delivered with a few hundred thousand payrolls and by the time of 5 release, it’s going to touch $500,000.
What is going wrong?
The moral of the story says everything in one line: “Slow and steady wins the race”. Yes, it all because of overconfidence. Everyone wants to hit the market first or release the app asap with the statement “We can clean it up later” and they can’t go back for cleaning the things up because now we have the new feature, new release so maybe next time, next time and next time.
The only way to go fast is to go well.
To take the software architecture seriously we have to think and need to know what good software architecture is, compare the different architecture with the requirements.
Thanks for reading it, if you want to read in more detail, buy “Clean Architecture by Robert C. Martin”
image source (google.com)
Let’s say you work as a company secretary and your job is to take the phone calls, manage meetings etc. Every time the phone rings, you have to stop whatever you are doing. A property of a program that allows tasks to run in overlapping time periods.
- Parallelism, allows 2 or more tasks to run at the same time (Only if the machine has the multiprocessing capability). You asked your boss and he hired a clerk for taking the call. It looks very simple but concurrency introduces a few problems like the Race condition,
- Race Condition, Suppose you have $500 in your bank account, at the same time when you withdraw $200 someone transferred $300 or maybe in simple words same time 2 transaction happened for withdrawing $500.
- Mutual Exclusion (Mutex), Solution for the Race condition. Now, whenever some transaction starts it locks the account. if some transaction is going on with your account you cannot withdraw. But next problem is nobody wants to wait every time when there’s is something going on. Semaphore is the modified solution for Mutex.
- Semaphore (Improper use of Semaphore will give improper results)
- Binary Semaphore (Range is from 0 to 1), Idea is to give specific priority to different types of transaction. Withdraw request has a higher priority than bank transfer. So when you withdraw, another transaction for transfer will stop and it will resume once withdraw is completed. (As simple as that, 1 = ongoing transaction, 0 = waiting) Also known as integer semaphore.
- Counting Semaphore (Range is from -∞ to +∞), Allow more than one process running at the same time. Let’s suppose you’re a key room manager where you have 30 keys if lockers are full users have to wait in the queue. when someone has done they will hand over the key to the first person in the queue.
- Deadlock, Another common issue in concurrency modal. Let’s assume user a transferred amount to b and at the same time user b transfer the amount to the user a. both transactions are waiting to complete another one as they can’t access the locked account.
- Structs are the value type.
- Classes are the reference type.
- Properties of a constant instance of the struct are immutable because struct’s instance own the whole object and by declaring it as a constant means the whole object itself will be immutable.
- Properties of a constant instance of the class are mutable as class’s instance owns the object’s reference thus by declaring it as a constant only means that the further reference assignment can’t be done.
- Structs are blessed with default member-wise initializer but classes are not.
- Structs are preferable when they are small and copyable.
- With Structs, there is much less need to worry about memory leaks or multiple threads racing to access/modify a single instance of a variable.
- Since struct instances are allocated on the stack, and class instances are allocated on the heap, structs can sometimes be drastically faster (but it still depends on how many values you’re storing and the size/structure.)
- In a multi-threaded environment, for instance, with a database connection that’s opened in a different thread, structs are safer. They can be copied from one thread to another thread, without running the risk of a race condition or deadlock. Classes do not have this inherent safety unless they’re deliberately made thread-safe.
Thanks a lot for reading it.