This repo provides common roadmap for characterless iOS developers climbing to a higher level.
Feel free to add PR or issues.
Basic tools
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Languages
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Business related
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Linter
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Test related
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Profile tools (Performance related)
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Building related
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CI/CD related
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Render
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Debug related
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Hotpatch / HotReload
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Crash related
| Safety related
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System domain (XNU)
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Functional programming
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As this repo is written in English, English part is ignored.
This section recommends several useful google search tips with little effort to learn.
Check them out in:
I strongly recommend using "", -, *, ~, site:, filetype: etc.
Git will be your best friend in your whole career. pls learn it staidly in this official site.
Be sure you can explain following commands:
- git add
- git add -i
- git add -p
- diff between git add -u & git add -A & git add .
- pull
- git pull -r
- git pull -squash
- diff between git pull and git pull --commit
- git pull --edit
- git pull --autostash
- push
- git push -f
- git push --prune
- rebase
- git rebase --ignore-whitespace
- git rebase --signoff
- worktree
- git worktree add / remove
- git worktree list
- git worktree lock
- git worktree move
- cherry-pick
- revert
- gc
- stash
- git stash pop
- git stash save
- prune
- blame
- restore
- diff
- cogfigurations in .git/config
Charles satisfy most need in daily development, but if your app uses a stronger network framework than http1.1 or http2 like QUIC, you should switch to wireshark.
Best relacement of terminal and bash for now.
VScode now doesn't support for ObjC or Swift well, especially bad support for ObjC. But LinkedIn has been transfered to swift for a long time, I found there are more and more plugins supporting for writing swift code in vscode and even there is an official swift plugin in progress. And the most important reason for me to use vscode rather than xcode is that xcode's indexing system is getting slower and slower. I can't tolerate such a stupid IDE and switch to embrace open-source tools.
There are too many vscode's tutorials, I only list an iOS related customization of vscode by nshipster.
Actually, as most of large iOS project contains many ruby, groovy, python scripts, using vscode and armed with useful plugins are basic requirement of an efficient iOS developer now.
Wait for someone or myself to introduce THIS F S.
So many people said Vim is useless nowadays but I'm still used to vim when git commit -m. Being familiar with common vim commands will help you in some corner cases you don't expect at all.
Choose a good music app, if any chance, don't choose netease music.
Figma is a good tool used by so many companies like bytedance, linkedin... Being familiar with this tool will improve the efficiency you get info from some design.
And Figma is an absolutely useful tool when you are demostrating your arch of some module in your project. Put some illustrations in RFC will also help reviewers understand what you are doing like the workflow, the layer arch or something else.
- ObjC
- objc message forwading, selectors, method swizzle
- objc class layout / ivars (fragile ivar, ivar encoding) / protocols / isa pointer / method list (class method and instance method)
- +load, +initialize, Category
- associated property
- stack block, escaping block, variable captured by block
- KVC and KVO
- tagged pointer
- ARC mechanism
- MRC and ARC
- autoreleasing
- weak and strong
- copy
- Swift
- frozen enum
- diff between NSArray and Array
- Any, AnyObject
- ?, !
- swift class layout
- struct
- protocol
- extension
- concurrency, async, await, actor model
- open, public, private, internal, fileprivate
- codeable
- property wrapper
- string solution
- POWERFUL generics
- C/C++
- Basic C programming
- C++
- Object model
- virtual methods
- virtual base classes
- EBO (empty base optimization)
- RAII
- exception-safe types
- Value categories
- lvalue
- rvalue & move semantic
- Smart pointer
std::shared_ptr&std::make_sharedstd::unique_ptr
- Template programming
- variadic template
- template template
- CRTP
- type erasing
std::function(application)
- Common optimizations
- SBO (small buffer object)
- RVO & NRVO
- Object model
- STL
- container types
- traits
- algorithms
- C++20
- modules
- coroutine
- concept
- Ruby
- Java/groovy
- Python/Shell
ObjC and Swift are most commonly used in daily development, as no language is simple, we should master in these 2 tools to cover wired issue you may meet in daily development. The language detail is also the foundation of dealing with complex problems like improving building time, improving debugging efficience, etc...
C/C++ are commonly regarded as having low overhead than swift and objc. And they all have good compatibility in different platform, widely used to create cross-platform frameworks like video, audio, networking, etc... Master in C++ will bring you capbilities to read complex computer science solutions like rendering or editing videos or playing audios.
Ruby is used by cocoapods which is the famous package manager nowadays. Podfile is something every iOS developer need to know in every large iOS project. Learning ruby and writing podfile or cocoapods hooks will help you understand iOS development easier.
Java and groovy are used by gradle and jenkins.
Python and shell are used to accelerate some specific problems like posting local crash logs.
Actually, most iOS developer call themselves UIKit caller. Just kidding.. But it does reflect the relationship between UIKit and development of iOS. UIKit builds every app's entire world. Each app has a UIWindow as the key window. Then we have to set up a root UIViewController of this key window. Then commonly we put a UITableView or UICollectionView in the root viewcontroler. Each row of the tableview or collectionview has some UIImageView and UIButton and UILabel and UITextView. Some of imageviews are set up with UIGestureRecognizers, then they can interact with users to respond to specific gestures. A simple but complete app is built done.
I don't want to discuss each classes in UIKit because there are too many. I only talk about following classes:
- UICollectionView and UITableView
- UINavigationController and UIViewController's presenting method
- UILabel and UITextView
Use UICollectionView for Horizental & Vertical scrolling. Use UITableView for Vertical scrolling. So if you want to implement an horizental scrolling UI element, you can only use UICollectionView.
The key improvement in efficiency in TableView or CollectionView is to reuse a UITableView/UICollectionViewCell without creating and destroying it. But it also brings us some "problems" in daily development, like forgetting to reset some UI related properties in prepareForReuse.
No matter UICollectionView and UITableView, under UIKit's MVC arch, we provide a datasource and a delegate for these 2 UI classes. Data source for data spec. Delegate for scrolling, sizing, configuring...
You can see delegate method is completely a ball of mud. IGListKit comes up to help you out.
The key concept of IGListKit is to seperate sections into several sectionproviders to release the pressure of controller. In raw UIKit, Controller takes all the responsibilities to run UICollectionView. Now with IGListKit, we have a manager called Adapter to manage all the resources UICollectionView needed. Resources are seperated into several parts, which is exactly sectionproviders. So our controller is clean now.
In addition to releasing pressure of controller, IGListKit also provides more coherence in one section. Most logics are put into ONE sectionProvider, the logics get bundled more tightly.
But in contrast to IGListKit's official guidance, I don't think section providers are easily to reuse. Actually, NO CONTROLLER CAN BE REUSED. The only thing we can reuse is the relationsip between view and model. Even the configuration can not be reused.
LinkedIn recently worked out a new UI framework which focuses on the relationship between UI and model, give up thinking of reuse of section controller or provider, the only thing designed to be reused is the relationship between model and view. And of course, the configuration can be reused optionally.
Another advantage of IGListKit is the high performance it provides with diff algorithm. No more reloadData. Only perform change from one snapshot to another.
But IGListKit doesn't fix the problem that we can call several times in one loop. But LinkedIn's one fixes this issue by a delayed update in one loop.
The interfaces of IGListKit still need to improve.
In addition, UICollectionView and UITableView's shared parent class, UIScrollView, also provides abilities to zoom content allowing your application to support the standard pinch gestures to zoom in and out. You should check this guidance before the actual feature implmentation.
Then is navigation and presenting. Transition between different pages are common need in mobile app, Apple designed UINavigaitonController to horizentally transfer from one to another, and presenting to verically transfer form one to another. The difference is that, navigation to next must cover current page. But presenting one doesn't require that. So we have modal presenting. I don't know how Android implements in transition between pages, but for me UINavigationController and the presenting behaviro are both not easy to use especially when you want to customize.
See this framework to learn more: CoreNavigation
For rendering text in iOS, I strongly recommend YYText to discover the principles behind UILabel with CoreText API. YYLabel provides strong feature and is easy to debug with transparent code. In one word, either YYLabel or UILabel are just wrapper for CoreText. CoreText doesn't provide the canvas, we need a UIView to provide the concrete canvas, so thats YYLabel or UILabel. With exploring of the implementation of YYLabel, you will learn Font, glyph, CTRun, paragraph, baseline and other concepts. As computers now still transfer infomation by rendering words, don't miss these exciting part!
Then let's talk about rendering images. Basically, UIImageView is the only one responsible for rendering images in iOS world. But it doesn't support SVG, WebP at all. You need a third party decoder to process such types data like SDWebImage/Webp.
SVG or PDF are designed to provide an interactive zoom-in/out experience with high-fidelity based on vector graphics. SVG is based on XML which means a big SVG still can be compressed smaller in binary format. And you can search, edit the content with raw text editor or drawing software. I won't describe the advantages and disadvantages of vector based format compared to bitmap based format, try to search and learn by yourself.
In addition, on a whim of investigating the implementation of SDWebImageSVGDecoder, I found SDWebImage tries a shortcut instead of implementing a concrete decoder on iOS platform. It uses CoreSVG framework which is still in beta and protected by Apple. It reverses the CoreSVG framework, gets the interface of the key functions, and uses dlsym to open these functions at runtime. To implement SVG decoder and renderer in iOS platorm, we can use libXML to parse the SVG file's data, use CoreGraphics to render all the bezier path defined by the data. SwiftSVG provides a traditional way to achieve.
For PDF files, use UIGraphicsPDFRender to render a PDF file.
Sometime we need to render some AE-based visual effect, like a piece of animation. We can complete this taks by UIKit. Lottie and PAG say hello. Generally, Our designer works on AE, Lottie and PAG are responsible for render designed work from AE to iOS platform. Lottie is developed by Airbnb, stable enough, but also with many problems. PAG is rencently released by Tencent, freshman, but decalres sovling problems in Lottie, like high memory pressure, lack support for new AE features, etc.
Lottie is based on CoreAnimation. It creates many CALayers to immitate the effect in AE's definition. Complex effect consumes much cpu and memory, especially for scenes with more than one complex Lottie animations. You need to take care of each animation's resource management, cut the cpu consumption peak due to decompress so many images used by animations. In addition, lottie in objc was stopped to maintain for many years, many features are not supported in objc version but in swift version like resource provider which is extremely useful when rendering complex aniamtions or doing some customizations on animations.
As we refered CoreAnimation, let's talk about rendering in iOS. Rendering can be divided into 2 parts in iOS platform, CPU based and GPU based. Strictly speaking, CoreAnimation has little relationship with manipulating on GPU. Because CoreAnimation performs more like an broker between App and system concrete rendering service. App -> UIKit -> CoreAnimation -> system render service (backboard or springboard). The actual rednering behavior is done in system render process. The render process manipulates on GPU. But CoreGraphics works as a slave, when we call it to render something, it does actually render in App's process, like creating a buffer, and filling it with colors.
CoreAnimation provides CALayer which represent a minimum unit to render. Try regarding a layer as a part of screen. Layers can overlap. CoreAnimation also provides so many subclasses inherit from CALayer to achieve different visual effect or provide back support for UIKit's related classes. Frequently used classes are:
- CALayer
- CATextLayer: rendering text without UILabel. UILabel uses _UILabelLayer inherites from CALayer directly.
- CAGradientLayer: designed to achieve gradient color effect.
- CATiledLayer: commonly used in optimizing big picture rendering like
微博长图.
CoreFoundation and Foundation perform as the foundation of the entrie iOS system. CF performs following roles:
- Data structures provider. It provides like CFArray, CFDictionary, CFTree if you are programming in C.
- Practical utils provider. It provides CFLocale, CFXMLParser, CFDate...
- IPC Wrapper. Use CFMessagePort or CFMachPort to communicate with other processes.
- Low-level Network provider. You can use CFSocket to do socket level networking requests.
- Runloop provider. CFRunloop is the key role in any applications in XNU.
Check CoreFoundation's headers if you wish.
CoreFoundation is wholely open-sourced by apple. See it here
There are 2 classes I want to explain here:
- CFMachPort
- CFRunloop which are considered the most special classes provided by XNU.
CFMachPort is used to communicate with other process. One process sends a message to another process. Message is sended and received by 2 mach ports, one in the sender process, another in receiver process. Almost every system framework relies on IPC to work with others. Even our app relies on IPC to achieve goals like rendering something, handling user interaction, handling networking notifications and so on. But almost all these IPC behaviors are covered by system framework. You can see nothing in the opaque UIKit about IPC or NSURLSession in Foundation.
Check more details in these links: hurdextras A demo of register disk mount/unmount notification from system by mach port Some investigation of system notification in Chinese Communication between our server and client Implmentation of registering local and remote port when communication
If you checked the last but the most important one, you will find bootstrap_look_up2 and bootstrap_register2 and task_get_bootstrap_port which will bring you to the concrete XNU's implementation which differs a lot from unix.
Then is runloop. Runloop is something highly investigated by now. If you are still strange with it, check this official doc and source code of __CFRunLoopRun
- GCD/NSOperationQueue GCD provides:
- Parallel task execution and synchronization (Queues and Tasks)
- Thread Scheduling (QOS)
- System Event Monitoring and Time
The first 2 abilities are well known by most apple developers. dispatch_async and dispatch_sync are widely used in every application in Apple ecosystem.
The concepts of queue and tasks have been well explained by Apple's archived docs – Concurrency Programming Guide
You must become familiar with queue, async, sync, barrier, group and semaphore before any real development in iOS.
But for the third one, System Event Monitoring and Time, are rarely used, but very powerful when you are fixing specific problems like:
- Timer
- Unix signal
- File/Socket descriptor
- Process related events, Mach related events
- Customized event
Find details in Dispatch Source
If you feel a little bit hard to understand these APIs without examples, you can check an apportableFoundation who implements Foundation.framework's API with CoreFoundation and GCD. And CoreFoundation uses GCD too. For example, if you are looking for dispatch_io related examples, check NSFileManager's implmentation in this repo; if you are looking for dispatch_source mach port related examples, check CFMessagePort/CFMachPort's impl. Also, GCD actually works tightly with CFRunloop to perform runloop-based behaviors like dipatch task to main queue which is also the main runloop.
AFNetworking
AFNetworking saves our time to write template codes like requesting an image for a UIImageView, UIButton, or binding UIActivityIndicatorView, UIProgressView and UIRefreshControl with some specific network request. It also provides abilities to:
- customize your strategy about server trust certificates.
- reuqest:
- simply map random string to be a legal query param (
AFPercentEscapedStringFromStringused by AFQueryStringPair) - automatically set
User-AgentandAccept-Language - simply create multipart request with automatically set
Content-TypeandContent-Length
- simply map random string to be a legal query param (
As for response, IMO AFNetworking doesn't work as well as we wish. First weakness is lacking of response modeling, AFNetworking just returns a raw NSDictionary if you are using JSONSerializer. AF does not provide a default modeling way to make the most convinience for users. Besides, AF doesn't support protobuf originally, but pb is almostly used by every application nowadays.
WCDB/FMDB(SQLite)/MMKV
CoreData
Keychain
NSFileManager/NSStream
JSONModel/Swift Codable/YYJSON
Protobuf
Remodel
ConsistencyManager
Regex
Deeplink/Router (no specific framework)
RxSwift/RAC
...