SheldonWangRJT

This notes is written by Sheldon. You can find me with #iOSBySheldon in Github, Youtube, Facebook, etc.

Need

Convert .mov/.MP4 to .gif

Reason

As a developer, I feel better to upload a short video when I create the pull request to show other viewers what I did in this PR. I tried .mov format directly got after finishing recording screen using Quicktime, however, gif offers preview in most web pages, and has smaller file size.

This is not limited to developer, anyone has this need can use this method to convert the files.

SheldonWangRJT

iOS Create a Carthage Supported Framework

#iOSBySheldon
A little bit Background of Carthage:
- Carthage works like Cocoapods, but a little bit simpler. 
	* When creating a Cocoapods supported framework need a .podspec file to do some config, which is not required by Carthage.
	* When using a Cocoapods supported framework, a workspace file will be automatically created, the umbrella header will be setup in a pod project inside workspace. It feels simple, but the whole process creates a lot files including a "giant" workspace.
	* When using a Carthage supported framework, it will just download the framework, and its dependencies if any, to a folder. All we need to do is to drag and drop it to the binary linking section in the project build setting tab, for the first time. It sounds complicated but it makes the project clean.
- Carthage is written in Swift. 
- Carthage internally uses `-xcodebuild` to build dependency.

SheldonWangRJT

In WWDC23 https://developer.apple.com/videos/play/wwdc2023/10226/, the new debugging was released.

import OSLog

let logger = Logger(subsystem: "You system", category: "Account")

func doSomething() {

 logger.info("start")

SheldonWangRJT

#iOSBySheldon #objective-c #swift #unitTest #uiTest #sleep

This notes is written by Sheldon. You can find me with #iOSBySheldon in Github, Youtube, Facebook, etc.

The only reason that I wrote this short quick note is that, the answers on the internet is somewhat misleading.

If we are running sleep() usleep() or [NSThread sleepForTimeInterval:] in your main app, there should not be any difference. Because the first two functions are just functions that from c and the third one is from objective-c.

However,

• You probably should NOT call them in your main app, because for delay operations you should more use (in Swift)

SheldonWangRJT

iOS Dynamic vs. Static Library / Framework

Find me on Github, Facebook, Youtube, etc by #iOSBySheldon.

Concept

Library and Framework are not same but close. Frameworks are just libraries with linking (binding). In other words, frameworks are just libraries that are bundled into targets. Therefore, their file extensions are different.

File Format

• Static Library - xxxx.a
• Dynamic Library - xxxx.dylib

SheldonWangRJT

iOS Device Types, Names, Resolutions (points)

DEVICE TYPE	PRODUCT NAME	RESOLUTION (PIXEL)	UIKIT SIZE (POINT)	ASPECT RATIO (H:W)	UIKIT SCALE	PIXEL PER INCH (PPI)
iPhone1,1	iPhone	320 x 480	320 x 480	1.5	1.0	163
iPhone1,2	iPhone 3G	320 x 480	320 x 480	1.5	1.0	163
iPhone2,1	iPhone 3GS	320 x 480	320 x 480	1.5	1.0	163
iPhone3,1	iPhone 4 (GSM)	320 x 480	640 x 960	1.5	2.0	326
iPhone3,3	iPhone 4 (CDMA)	320 x 480	640 x 960	1.5	2.0	326
iPhone4,1	iPhone 4S	320 x 480	640 x 960	2.0	1.5	326

SheldonWangRJT

Git - Rebase and Squashing

#iOSBySheldon
It is pretty often that you notice your feature branch has way too many commits right be fore you merge to the Master branch.

If you see your git history of your branch, it might be like:

History:
Commit xxxx1 "modified 2 more tests"
Commit xxxx2 "updated first test"

SheldonWangRJT

iOS CPU and GPU basics

#iOSBySheldon #CPU #GPU #60FPS #CADisplayLink

Apple always encourage us as iOS developers to try to maintain our apps running with a 60 frames per second rate (60 FPS) to make sure the best user experience. Most of the time, this comes for free because the hardwares are getting better and better.

But in some cases you may need to dig deeper if your app as a significant frame drops to fix it for the users, which leads to my post today - the basic of CPU and GPU in iOS. Whenever I encounter this kind of question, I always want to find the answer directly from Apple’s official document. I was able to find this article here. I mean this article is written mainly for #Metal and iOS game developers but I found all the info that we need. As always, I will try to summarize the best part of the article.

SheldonWangRJT

High Order Functions in iOS Swift

Written by Sheldon, please find me with #iOSBySheldon in Github, Youtube, Facebook, etc.

It is exaggerating to say we don't need to use for loop or while loop any more but we can take advantage of the Swift language built in functions to do loops. If I give you a question now. Q: Assuming we have an optional nested array, please calculate the production of the values that are less than 5. let numbers: [[Int]?] = [[1, 3], nil, [2], [5, 10], nil, [4]], what is your best approach to do it?

And you know the solution that I am talking about is following Swift functions:

1. Map
2. FlatMap / CompactMap

SheldonWangRJT

iOS Swift - Cancellable Task with GCD

#iOSBySheldon

I think most of you guys know GCD pretty well. Basically, GCD is a high level API to handle multi-threading operations. We use GCD almost on daily basis to switch thread and execute codes like:

DispatchQueue.main.async { //execute some codes here } 
//switch to main queue and execute codes asynchronously

DispatchQueue.main.sync { //execute some codes here } 
//switch to main queue and execute codes synchronously