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Now, before we talk about and NSCoder and how we can start saving our custom objects to file,
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we first have to understand a concept known as sandboxing.
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Now, here's a scenario. Say, if I have two apps which are running on the same phone and one of my apps, say, inside Clima,
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I have some malicious software. And I try to infect the other apps on the same phone and maybe
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my code's intention is to mess up the other apps, or maybe I'm trying to get secure data from the other
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apps.
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And if you're weather apps start stealing data from your banking apps on the same phone, then you have
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a huge problem.
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And so in iOS, this problem is solved by something known as sandboxing.
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So imagine that all of your apps on your phone live inside their own sandboxes. And a sandbox is nothing
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more than just a sheltered environment,
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or maybe you can consider it as a little mini prison for your app.
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So each of the apps has their own folders to store files and documents that are associated with the
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app.
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And so when your to do list app needs to save or retrieve data, it can do so by reading and writing to
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that Documents folder, but it can't get access to another apps document folder.
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Instead, what happens is that every time your phone syncs with iCloud or when you plug it into your laptop
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and you sync it with iTunes, then all of these document folders gets backed up, either online or locally
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to your laptop.
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So, say, if you go out and buy a brand-new phone, any data that your app has saved to that Documents folder
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doesn't get deleted.
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Instead, it will constantly sync with iCloud or with iTunes
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and it will remain available for you to be able to read and write to it and grab the data that's been
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stored in it throughout the lifetime of the app.
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So in other words, because you have this backed up permanent storage solution, it doesn't matter if you
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change phones, if you update your operating system,
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if you download new versions of the app, you still have your personal data safely stored somewhere where
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the app can get access to.
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Now, sandboxing doesn't just apply to individual apps.
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It also means that apps themselves can affect the operating system's code.
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So you can't write a malicious app to grab the secure data from the operating system.
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For example, the user's fingerprints or their contacts.
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And this is also one of the reasons why the iPhone is considered to be far safer and more secure when
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compared to other phones and other operating systems.
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But it also means that, sadly, you can't make cool apps that changes the operating system settings.
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So, for example, one of the apps that I really wanted to make is an app where when I turn my phone to
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be face down onto the table, i.e., when the proximity sensors detect that it's occluded, then I want my
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app to automatically switch my phone into to "Do not disturb" mode because it usually means that I'm either
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having a conversation or I'm having dinner or I'm trying to work on something, and that would be really
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awesome.
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But without jailbreaking the iPhone, which is really not recommended,
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there's no way of implementing this on iOS.
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So there's benefits to sandboxing and there's also a cost to sandboxing.
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But this is something that we have to work with as an iOS developer. And in the next lesson, I'm going
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to show you how to get access to your Documents folder inside your apps and how to start saving your
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custom objects to that directory.
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So for all of that and more on the next lesson.