iOS Development Interview Questions | iOS Development for Senior Developers

Summary

本次视频访谈的是David, 一个有6年开发经验的iOS开发人员。他谈到了WWDC会议上Apple公布的最新iOS 16功能,如锁屏小部件、实时活动更新和动态岛等。他还详细讨论了iOS开发中的并发、性能优化和测试的最佳实践。总的来说,这是一次对iOS开发及其最新趋势和技术的详尽而生动的概述。

Takeaways

• 🍏 WWDC是苹果的全球开发者大会，介绍iOS新功能，如SwiftUI的新导航API、锁屏小组件和实时活动。
• 🔑 Live Activities允许用户从锁屏实时更新应用信息，如共享出行应用状态或实时比分。
• 📱 David Zampier专注于iOS开发超过四年，参与了多个有趣的项目，如世界范围的行李追踪和流媒体应用。
• 💼 通过Touring工作，David得以与来自不同文化和国家的人交流，并为一家位于加州的公司工作。
• 🔄 Objective-C不再是新项目的首选，Swift和SwiftUI更受欢迎，但Objective-C代码仍可与Swift互操作。
• 📲 在苹果生态系统中，不同设备（如iPhone、Apple Watch、Apple TV）可以共享Swift代码，但需要不同的bundle ID。
• 🔗 Deep Link和Universal Link允许用户直接从网页或其他应用跳转到应用的特定页面。
• ⚙️ GCD（Grand Central Dispatch）和操作队列是iOS中实现并发的方式，允许后台执行多任务。
• 🧩 设计模式，如MVC和MVVM，对于构建易于理解和扩展的iOS应用至关重要。
• 🔍 TDD（测试驱动开发）是提高代码质量和结构的重要实践，通过先编写测试再编写功能代码来实现。
• ✨ 异步编程和最新的async/await关键字简化了iOS中并发任务的处理，提高了代码的可读性和维护性。

Q & A

WWDC是什么，今年有哪些新功能被介绍？

WWDC是苹果的全球开发者大会，今年介绍了新的SwiftUI导航API、锁屏的新小工具、以及实时活动等功能。

锁屏上的实时活动是什么，它怎么工作？

实时活动允许应用在锁屏上显示实时更新信息，如共享出行应用或实时比分等，也支持在iPhone 14 Pro和Pro Max的动态岛上显示。

如果我有自己的API，能在锁屏上显示数据吗？

可以，你的应用可以通过实时活动在锁屏上显示来自你自己API的数据。

Objective-C还在iOS开发中使用吗，还是已经完全转向Swift？

新项目和新功能主要使用Swift和SwiftUI，但因为Objective-C与Swift的良好互操作性，旧项目仍可能使用Objective-C。

iOS, watchOS, tvOS和macOS应用开发中有什么共同点？

这些平台都可以使用Swift进行开发，并且开发者可以在这些平台间共享代码。

什么是深度链接，它如何工作？

深度链接是指向你应用内特定页面的链接。使用通用链接，如果应用未安装，用户点击链接会被引导至App Store下载应用，安装后打开特定页面。

什么是GCD，它在iOS中用来解决什么问题？

GCD（Grand Central Dispatch）是一种低级API，用于在iOS应用中实现并发和并行任务处理，通过管理后台线程来执行多个任务。

iOS应用在后台运行时会发生什么？

当应用处于后台时，主线程被挂起，但后台线程可以继续执行某些操作，如使用用户位置或与服务器同步，但不能执行大量的处理任务。

App ID和Bundle ID有什么区别？

Bundle ID是应用在苹果生态系统中的唯一标识符，而App ID是由团队ID和Bundle ID组成的字符串，用于标识同一开发团队的一个或多个应用。

在iOS开发中如何提高应用性能或管理内存？

可以通过使用多线程、并发任务、懒加载属性等技术来提高性能和优化内存使用。

Outlines

00:00

😀 开场与iOS开发简介

视频以介绍主持人Jose和嘉宾David Zampier开始，David在iOS开发领域拥有超过六年的经验，专注于iOS开发近四到五年。讨论内容围绕David在iOS开发中的经验，特别是他参与的项目，如全球行李追踪、流媒体应用和社交网络应用。接着讨论了苹果的全球开发者大会（WWDC），David详细介绍了WWDC期间苹果发布的新iOS版本的新功能，如新的导航API、锁屏小工具、实时活动以及如何将这些新特性集成到自定义应用中。

05:02

🔄 iOS开发进阶话题

在这一部分，David讨论了iOS开发的更高级话题，包括Objective-C与Swift的使用情况、重要性和转变，以及开始iOS开发的最佳路径。他还详细解释了为不同苹果平台（如Apple Watch、Mac和Apple TV）开发应用时代码共享的概念。此外，他提到了深度链接（Deep Link）和大中心调度（GCD）在iOS中的应用，以及如何实现并发性和应用性能优化的技术。

10:04

🔍 iOS并发编程与性能优化

第三段深入探讨了iOS中的并发编程和性能优化策略。David解释了不同的并发技术，如调度队列、线程和操作队列，以及它们如何帮助提高应用性能。他讨论了将应用置于后台时的行为，包括何时使用用户位置和API同步，以及应用在后台的存活时间。David还区分了应用ID和包ID的概念，并提供了关于如何在不同的Apple平台上设置和识别应用的建议。

15:06

🛠️ iOS开发技巧与最佳实践

在这部分，David分享了有关iOS开发的技巧和最佳实践，包括如何使用懒加载属性来优化性能和内存使用，设计模式的重要性，特别是MVC和MVVM在iOS中的应用。他强调了测试驱动开发（TDD）的价值，并讨论了如何使用异步编程和完成处理器来处理iOS应用中的并发任务。David还提到了Swift中的async/await关键词，以及如何利用它们简化异步编程。

20:07

📲 iOS开发资源与学习路径

最后一段讨论了成为iOS开发者的资源和学习路径。David鼓励观众利用互联网上的资源，如Apple的官方文档和开发社区，来学习iOS开发。此外，他提出了动态派发和同步与异步任务的概念，并解释了它们在iOS应用开发中的区别和应用。视频以鼓励观众订阅频道并关注社交媒体账号结束，同时强调Touring平台上远程工作的机会。

25:08

🎉 结语与呼吁关注

在视频的结尾，Jose感谢David的精彩对话，并邀请观众订阅频道、点赞视频，并关注Touring在LinkedIn、Instagram、Facebook、Twitter、Clubhouse和YouTube上的社交媒体账号。强调了Touring提供的远程工作机会，鼓励有志于iOS开发的观众利用这个平台寻找合适的工作。

Keywords

💡iOS

iOS是苹果公司的手机操作系统,用于iPhone、iPad等苹果产品。视频里讨论了iOS开发的相关技术与实践。

💡Swift

Swift是苹果公司推出的用于iOS和MacOS应用开发的新编程语言,取代了过去的Objective C语言。视频中提到现在iOS开发主要使用Swift语言。

💡WWDC

WWDC是苹果举办的全球开发者大会,每年6月举行。苹果会在会上发布iOS等系统的新版本与新特性。

💡动态调度

动态调度是指程序在运行时决定调用哪个方法的实现的机制。当子类重写父类的方法时,动态调度允许根据运行时条件选择调用子类还是父类的实现。

💡异步

异步是指程序中多个任务可以同时执行,一个任务不需要等待另一个任务结束后再开始。视频中提到iOS中的异步编程可以提高效率。

💡gcd

GCD是Grand Central Dispatch的缩写,是iOS中的并发框架,可以更好地管理线程与任务,实现并发编程。

💡设计模式

设计模式是可重用的解决常见问题的编码设计。视频中提到MVC、MVVM等模式在iOS开发中的应用。使用设计模式可以提高代码质量。

💡测试驱动开发

测试驱动开发把测试放在首位,通过先写测试来驱动整个开发流程。视频中建议iOS开发要使用测试驱动开发。

💡内存管理

优化内存管理对提高iOS应用性能非常重要。视频中提到了一些实用技巧,比如延迟初始化属性等。

💡深度链接

深度链接可以直接在应用内打开指定页面。视频中解释了iOS中的通用链接实现深度链接的功能。

Highlights

苹果每年在WWDC大会上发布iOS最新版本和特性

iOS 16增加了锁屏小组件功能,开发者可以为用户自定义锁屏

iOS 16还增加了实时动态信息更新功能,可以在锁屏显示比赛分数或者共享汽车等实时信息

WWDC大会上,开发者可以与苹果工程师交流,学习新特性和新文档

目前iOS开发都使用Swift语言,尽管Objective C仍然支持与Swift的互操作

SwiftUI可以编写跨多平台代码,比如iOS, watchOS和tvOS

深度链接可以直接打开App中的某个界面

GCD是底层API,可以同时执行并发任务

后台任务会被挂起,但是可以继续执行某些操作,比如位置跟踪

iOS有调度队列、线程和Operation Queues三种实现并发的方式

延时属性可以根据需要延迟初始化,提高性能

MVC设计模式还是常用的iOS架构模式

测试驱动开发可以提高代码质量

动态调度是在运行时决定调用哪个方法实现的

同步任务会顺序执行,异步任务同时开始

Transcripts

[Music]

hello everyone we are back with another

round of touring Dev talks and today I'm

so excited because today talks is about

iOS development and I will be talking

with David zampier about iOS okay and uh

to give you a little bit of context

about David has over six years of

experience but for the past four to five

years he's focused on iOS development so

without further Ado hi David D how are

you doing and how is your day doing so

far

hey Jose thank you for having me I'm

really excited to be here today talking

to you about the iOS development so yeah

this is uh I'm doing great thank you and

let's talk about it nice so could you

please uh introduce yourself and talk a

little bit about your experience with

iOS what kind of project have you been

doing

so yeah I've worked for a lot of uh

interesting projects like uh worldwide

baggage tracking like for lost baggages

in airports also for streaming apps

um and social networks so yeah

so cool project a lot of cool projects

nice nice all right so and the first

question that I have to you today is

what is WWDC and what happened there

oh yeah so wwc is the worldwide

developer conference it's a conference

that Apple uh where Apple shows all the

new features for the new iOS version it

happens on June it's a whole week of

stockings and we can talk with uh

airport Engineers we can

study the new documentations we have

some uh working sessions and

where Apple introduces the new features

for us developers so this year we had

like the new Apple announced the newer

navigation API for Swift UI so we can

like build the navigation for our apps

in Swift UI more easily so we have the

new widgets for lock screen so if you

are using the new iOS 16 you can you

probably have seen it and you can like

uh build

um custom widgets for the lock screen uh

us as developers so also we have the

live activities and like screen lock

screen as well and all of these features

were introduced by Apple in www.dc this

year and and they like

um touch taught us how to build them for

our custom apps nice nice and what is

live activities on lock screen what kind

of features we have there

okay so a lot of activities uh Apple

introduced this year so basically we can

you can see uh real-time updates from

your app from your locked screen so like

for Rideshare apps or

um some you can see the score of a live

game in your lock screen so it's really

interesting and also it worked in the

dynamic Island introduced by Apple in

the new iPhone 14 pro and 14 pro Max

and so if I have my own API can I I see

data in my lock screen from my own API

sure for sure yeah you can do it in your

app all right so that is amazing so

could you please tell our audience uh

how you're working at touring has been

so far

oh it's it has been amazing like I've

known people from many cultures from

many countries and this is great because

I have opportunity to connect to people

from all the world

and uh I've been working for a company

based in California and they are amazing

they have like great Engineers there and

I had opportunity to be there a couple

of weeks ago to know the the the company

uh headquarters and to connect to my

teammates and it was awesome did you

travel to us last last week also yeah

yeah all right that's amazing yeah

that's that's so nice all right so in

talking about iOS okay the first

question that I have for you is so I use

iOS I used to develop for iOS long uh

years ago long time ago and I use

Objective C okay and is objective c is

still using nowadays or they are using

only Swift

yeah so for new features and new

projects we are only using Swift and

sf2i maybe but because uh objectivity C

has a great interoperability with swift

so if you have like a code reading like

a few years ago you can like it

communicates with Swift in a great way

so we're not using objectives anymore

just for like old projects but we are

still migrating from your objectivity to

serve because it's way better in my

opinion nice and yeah and do you think

that it's important for developers to

know objective see if they want to start

in this world or they they must start

with Swift and then go on

I think they can start with swift

nowadays because as I said they're like

the new projects and the new features

that we're current building like they

are all in Swift but there are some

projects that still use this objectivity

so maybe at some point they will need to

like study a little bit about

objectivity but for starters I think

it's probably the best way to start with

swift just to understand a little bit

right

yeah all right all right all right so

um could you please

um explain me okay what what are the

main difference between uh you create

one application for Apple watch for Max

and for Apple TV and for iOS and so on

for example

yeah so uh basically we can use apple

uses Swift for all of its platforms like

uh iOS that it's the the OS for the

iPhones for watch OS for app watch the

TV OS that it is for Apple TV so

basically we can like for iOS we can

build an app for iOS and it can run

share the code with the Apple watch or

the iPads or even with the Mac OS so we

have great uh things

um a great ways to like share the code

between all the platforms from Apple

nice really nice all right and what

could you tell me about uh deep link uh

in iOS what's deep link

well so deep links uh there are links

that are used to send users like direct

to a point of your apps for screen or

something like that so

um

Apple introduced us the universal links

that's a new approach to connect your

web page

so we are uh to our app under the same

link so if you click to a universal link

and your app was set up with this new

this new Universal link API so instead

of if you don't have that installed on

your iPhone you'll be redirected to your

like the App Store so you can download

the app and open the app right on the

page that you are looking for that's

nice so let's suppose I am on touring

webpage website and then to the says uh

download our app and then when I click

in this link it will try to it will

check if I have this uh app installed in

my device if not it will redirect to uh

Apple Store in the app page when I click

and download it will download and open

the the app is that

yeah yeah basically that it's amazing

nice all right next question I have for

you okay uh what is gcd uh gcd and iOS

in general

okay so DCd stands for Grand Central

Dispatch it's a low level API that

enables users to run concurrent tasks

like a current

simultaneously by managed tradings

threatens in the background so today we

have uh lots of complex apps that needs

to run simultaneous tasks so the the gcd

it's a apple solution to build the

concurrency and parallelism into iOS

applications and so you can run multiple

tasks in background simultaneously and

this will not affect like the main

thread or your main app so you can still

using like your features while other

things are currently are happening in

the background

all right okay got that but

um so how we can achieve uh concurrence

in iOS so is that the only way to do

that or there's or is there any other

possibility

okay so basically we have three ways to

achieve the concurrency so one of them

are the dispatch queues so they are used

to manage uh tasks like my fifth order

first in First South where they can

basic execute it sequentially or

concurrently this is an easy way to

handle a secret a synchronous tasks in

your application you know so the second

way we can use threads so we can start a

thread and like uh run a code in this

separated thread and it will run uh

concurrently with the main traged that

of that or your app can have like many

threads

and having a threat is special it's

useful uh when you need to perform uh

some tests that it will take a long time

to to run you know

and we have also the operation skills

the operation queues they are high level

abstractions they were built on top of

the gcd that we talked before and it is

possible to

execute tasks like concurrently just

like this the gcd but in object-oriented

manner

all right so then I have two dummy

questions for you okay I hope you don't

kill me about this question but yeah so

first question

um what happened when you put our app in

background for example if I'm using 2D

app and then I just uh swiped up and

then go to the main page what what what

happened and what what can I do there

okay so basically when you put your app

and background uh the main thread it's

like suspended and the background

threads can uh perform some actions that

you are explicitly say to perform so you

can uh continue using the user's

location for Rideshare apps uh in

instance so also you can have like some

kind of synchronization with your

um background back end or if you or with

your API but you cannot perform like

have your uh have tasks like that

demands among a lot of power or energy

or processing from your app from the iOS

you know yeah and how much time our web

can stay in the background

so it's defined by the iOS the iOS

defines how much time your app can stay

alive in background

it depends on your available memory the

processing the app that is currently in

the in the foreground like is running

uh active at the same at the time you

know so it's defined by the iOS all

right in my second question for you is

what's the difference between app ID and

bundle ID

okay so the bundle ID is uh it's the

unique identifier for applications in

the whole apples ecosystem so we have

the bundle identifier for your IOS app

the bundle identifier for your

uh watch OS app for your Apple TV app so

they are for the whole Apple system uh

they use it they are used to reckon just

to recognize your app and for updates

and this kind of stuff and the app ID

it's a string that uniquely identifies

one or more apps from the same

development team so we have uh

development teams for the Apple

developer and uh this string the app ID

has two components the team ID and your

bundle ID from your app

got you so so if you have one

application that runs in my my cell

phone and another one that runs my Apple

watch so how can I set up it and to

identify they are the same

yeah so we will need to set a different

bundle identity a different bundle

identifier for your iOS targets we call

it Target so we have the iOS Target and

the watch West Target so we you can set

them separately different they must have

differently okay bundle with two

different bundle ID and when it comes to

the app ID

two different two

yeah exactly because you get the bundle

ID and the team ID the team ID will be

the same but the bundle ID will be

different all right so in terms of

performance uh what techniques we can

apply in our app to improve the

performance or the user the the managing

memory and stuff like that in our

application

okay so well we can do a lot of things

while we are creating a new feature

developing our code so we can use like

uh multiple threads I start processing

different threads or background threads

so we can do uh some hard work uh in the

background or if you have to do lots of

API calls you can use uh

simultaneously using concurrency also

you can use uh lady prop lazy properties

and a lot of

stuff nice nice and speaking about lazy

property what's lazy property

okay so the latest properties are

properties who's the initial value isn't

computed until the first time they are

used so you just need to include a lady

a lazy a modifier to your Declaration of

your property and this lets uh this will

delay the initialization the

initialization of this property so this

is a a good thing to

save your memory or save energy because

if you have a property that needs to do

some kind of uh uh work hard work or you

can reduce this unnecessary work like

you know so it will be computed just

when you use it in your code your call

it your function or something like that

nice nice all right and when it comes to

design pattern okay do you think design

patterns are important nowadays if so

what design pattern are they using and

if not what should they do

okay so I think design patterns are

really important for most uh all the the

software development because it allows

us to uh make our code more

understandable and you can add more

features in an easy way

and specifically for iOS development you

can use a lot of different design

patterns

um so

when for the UI kids apps uh Apple

always like tried to use the MVC the

model of your controller uh it's where

we can like have mainly three components

like the view uh the controller and the

model

um the view is what the user sees uh the

controller it's everything that controls

this view or get information for it and

the model are your models for your app

and

we have the mvvm that's commonly used

for the new Swift UI where we have the

model view the model where the model is

are the models from your app the view is

what your user sees and the view model

is what connects your view

to your model that's why it's called

view model but for iOS we can use lots

of other design patterns like Singleton

uh Builder and many others got you and

when it comes to testing okay what are

the best practice in terms of testing

your application

is DDD bdd any of this design pattern or

these techniques use it or is there

another one that you recommend

oh yeah so tdd is really important to

use I think in my opinion because it

allows us to plan the features and build

the features already with your tests so

basically we will we start developing

your feature by the test so you create

your tests let them fail because you

don't have your classes yet so and then

you implement your code and you run the

test and if your test passes you can

improve your code and this is amazing

because uh we can gain sites into both

quality of the implementation if it is

work and the quality of design if it's

well structured and it's a good a good

code that you have reading you know all

right yeah I totally agree with you so

tdd is really important not only to

debits as much as you test your

application you will avoid further

problems believe me yeah all right and

and the next thing that come to my mind

is to talk about complexion handle okay

uh what's completion Handler

well uh completion hinders uh are

basically just functions passed as

parameters to other functions so they're

using to dealing with response of a

synchronous task since we we do not know

like when it will end so we use a

completion Handler to perform uh an

actual after your asynchronous code was

uh uh was run and but now we have the

new synchronous uh the swiftest

synchronous API that we they introduced

the async uh await keywords where you

can like uh using them you don't need to

use the completion handles anymore nice

yeah it's pretty uh pretty similar what

they are doing with uh c-sharp and

JavaScript as well so you can just think

a way to introduce that in JavaScript

and that's pretty great all right and

before we go to our next question I

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clicking in the bottom below and come

back to you David what do you understand

okay what could we tell us about Dynamic

dispatch

okay so in simple terms Dynamic dispatch

means that the program designs decides

at the runtime

which implementation of a particular

method or function it needs to invoke in

the case where a subclass overrides a

methods or if it's upper class Dynamic

dispatch there means determines whether

to invoke the subclass implementation

of the method are the parents it takes

more time like it it makes your code a

little bit slower using the dynamic

dispatch okay so previously we talked

about async await right which were a

great addition in iOS developing the iOS

world and so but I think I wait is for

uh can I say for asynchronous operations

or asynchronous tasks right but uh if

they are starting with iOS from now okay

from this video what do you understand

about the difference between synchronous

and asynchronous tasks in iOS how can we

explain it to our audience

okay uh so for synchronous tests uh they

are performed one at a time therefore uh

other tests must wait until the previous

task is completed before continue

for a synchronous tasks there runs

simultaneously in the background so if

the if background texts are completed

you'll be notified and a synchronous

programming allow us to process mood

proquests at the same time so you can

accomplish more tests in a shorter

amount of time you know okay let me see

if I get that so uh synchronous tasks

means it will be executing in the main

thread and then it go one by one let's

suppose you have a table uh with 10

lines and then you want to uh iterate

over this table it will be executing the

main thread and you go for line one and

then do whatever we need to do then line

two then line three line four and then

so on correct but asynchronous means

that it will be executed in a different

thread or the same thread as well

because this is I'm a bit confused so

different threads and then I can go for

uh execute that I can read the 10 lines

at the same times in different in in 10

different process and when it process

each process finish it will send me a

message is it like that

okay so the synchronous test not

necessarily will be

um uh run in the main thread I mean you

can start like a synchronous synchronous

tasks in a background thread so it is it

is possible and for the a synchronous

test they are start they start at the

same time I mean like one doesn't one

test don't need to wait to the other

test to finish so all of them start at

the same time in different queues and we

can like start for all of them to finish

to continue our code you know you can

get notified when all of them are

finished oh got you so then I have

follow-up questions so we wait we will

be notified when all of them uh finish

processing or one when each one so if

you want finish we will be notified and

then another one thing to be notified

you can have both behaviors it depends

on your implementation but you can get

that fire when all of them are completed

or when a specific one is completed nice

all right yeah you clarify my mind thank

you all right and as that said that was

my last question and then I just want to

ask you if you have anything to add okay

uh resource did that if they are

inspiring to be a iOS Developer like you

and work at tutoring where they can

learn uh what they could learn about iOS

what what's the best place to learn

about iOS well so we have a lot of uh

things on the internet so I mean we have

the Apple documentation we have a lot of

great uh blogs like uh talking about iOS

development so they are great resources

for us to understand and to learn about

iOS development in general in the

community community is really great you

know with this we come to the end thank

you Dave for this amazing talk okay that

was my pleasure to talk with you today

oh thank you Jose it was a pleasure uh

being here today talking to you thank

you for everything

cool I hope to see you again soon okay

and to everybody else so don't forget to

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thank you and hope to see you all again

take care foreign

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