iOS Concurrency and Threading - iOS Interview Question - Swift

The next topic in my series on iOS Interview questions explains concurrency and threading in iOS and Swift. This iOS interview question was asked in quite a few interviews. In this concurrency and threading tutorial I explain what is going on at a high level to help you answer this interview question.

This is part of a series of videos about iOS interview questions in Swift. Check out the overview where I list and briefly discuss all the topics that are in this series:

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Book and learning recommendations that help out the channel if you decide to purchase (Affiliate Links):

Paul Hudson's Hacking With Swift:

Donny Wals - Combine:

Mark Moeyken’s SwiftUI Books:

Ray Wenderlich Books:

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[wensmusic]

Dude you are an amazing teacher. I really enjoy your teach style, you bring real life examples into code and that really helps with bringing things into perspective. Thank you for taking your time out to teach us all of this. I have an interview tomorrow and I feel so much better now that i've seen your series and I know that i'm hitting on the right topics and that I actually understand them. Thank you bro

[richardgmartinonline]

Hi Sean: Job well done. You obviously put quite a bit of time into this video. The explanation is very clear and understandable.

[adeadegoke]

I am upset that 2 people have disliked this tutorial. I can not understand why. Anyway another great tutorial Sean. Keep it up

[pawelpow]

The car highway analogy is the best one I’ve heard so far. You are awesome! You always provide the best explanations

[seanallen]

Concurrency and Threading can be a tricky topic. Happy to help answer any questions in the comments!

[hariharanjagan]

i have 8 years of experience in iOS and you videos are simple & great examples

[wanted]

I’m listening to this while I’m on my way to a technical interview after learning iOS Development for almost a year with zero coding background. Great stuff Sean!

[bibinjaimon]

I've seen this video 3 years ago. Now again came here to recollect things. Thanks for making this video🙂

[beastgenv]

That was pretty solid explanation once again, I have been learning iOS Development for the past 6 months now and watched almost all of you videos, great work. Every time I learn at least a thing I did not know before. Thank you.

[raousama]

you explained all this in a very simple manner...good job done

[atomueki]

A lot of developers don't have a strong basic knowledge now days and this kind of videos really helps, appreciate it, like your videos, thanks man and keep going!

[chillybean]

Wow this is awesome Sean. Nice use of animations and your explanation is very clear. Keep up the good work, Nice one here!!

[mrmillmill]

Great videos! I enjoy your paid courses as well! Very thorough and well executed Sean. Question: what are a list of tasks that happen on background threads vs a list of tasks that happen on main thread? My understanding is closures occur on a background thread and updating UI happen on main thread. Any other logic, tasks, methods etc that directly link to background thread or main thread? Basically, what are the dead giveaways in code that state, ”This is background thread or main thread?”
Also, what allows you to see what thread something is occurring on? Is there code that will reveal that? Like code for checking type(of:) for data types tells the data type…is there something similar to understand which thread is used for code?

[ambujpunn]

Great video Sean. I had a question: You mentioned that you don't manually put anything on the background queue as much...Why is that? I would say it is common practice to manually put API data fetching logic in the background queue. And the only reason one should have to call reloadData for the table view on the main queue is when something has already been put in the background queue (like a manual trigger to fetch data through some API)

[MarcosFelipejchrist]

Thanks for video .
Its the best video about GCD I've ever seen.
The video is excellent, audio is great and you can show with animations and codes.
You're doing the fantastic work. Congratulations for your work

[andreadavid]

Hey Sean, such an excellent explanation for me as a beginner developer. I wasn't expect that you use a lot of some kind of real-life example like the highway and the queue but you did, so that's nice and very much easy to understand compared to coding. Thank you very much and keep up the good works!

[karooki]

Hey Sean! Absolutely love your videos! Currently just went through a phone screen and 80% of the questions came from your videos so I'm really thankful! Just wondering, what you use to make your animations?

[filipsardjoski]

Excellent work! Animation and visual explanation helps a ton 😊

[batuhankrbb]

I just want to tell you that you are rock! I really love your courses, videos and contents. Keep going

[genebogdanovich]

Sean, thank you for making these videos! Keep it up!