Speaker 1: Welcome back to the deep dive. Today, we're really jumping in,
Speaker 1: launching straight into the well, the bedrock of the Apple ecosystem.
Speaker 1: Our goal isn't just to skim the surface. We want
Speaker 1: to pull out those foundational pillars, the architecture, the tools,
Speaker 1: and really the philosophy behind Swift.
Speaker 2: Yeah, the core ideas exactly the.
Speaker 1: Stuff any aspiring iOS dev needs to get. This is
Speaker 1: about understanding the why behind the code.
Speaker 2: You write, right, And I think for anyone starting out,
Speaker 2: the key takeaway is that Swift isn't just another language
Speaker 2: thrown out there. It was built very deliberately with specific goals.
Speaker 2: Specific goals safety, clarity, and performance that shapes everything, how
Speaker 2: you declare variable, how memory works, all of it.
Speaker 1: Okay, so let's unpack that starting big picture. Yeah, an
Speaker 1: iOS app. Yeah, it's like its own little world, right,
Speaker 1: what's at its core?
Speaker 2: Fundamentally, you can think of any app as having let's
Speaker 2: say three main parts the screen what the user interacts with, Okay,
Speaker 2: the code, the logic, the instructions, and the data the
Speaker 2: information it holds onto screen code data simple enough, and
Speaker 2: the whole thing operates in what we call an event
Speaker 2: driven paradigm.
Speaker 1: Right, Event driven. That's important. It's not just running top
Speaker 1: to bottom like a script, not at all.
Speaker 2: The phone or iPad is basically just sitting there waiting,
Speaker 2: waiting for an event like a button tap, a button tap,
Speaker 2: a notification, maybe a timer firing. Something happens. The operating
Speaker 2: system catches that event, figures out which bit of your
Speaker 2: code needs to handle it, and runs that.
Speaker 1: Code, and that code changes something always.
Speaker 2: It leads to a change in state, maybe updating what's
Speaker 2: on the screen, maybe changing the stored data. This constant
Speaker 2: loop weight respond update. That's the pulse of an iOS app.
Speaker 1: Got it, and the place we orchestrate all this code
Speaker 1: UI configuration, that's xcode. Can you walk us through the
Speaker 1: essential parts of that environment. It can look a bit
Speaker 1: intimidating at first.
Speaker 2: Sure xcode is your main hub, your ide. Think of
Speaker 2: it in like four main zones you'll use constantly. On
Speaker 2: the left, the navigation pain. That's for finding things, your files,
Speaker 2: your classes, images.
Speaker 1: All that, your project structure exactly.
Speaker 2: Then the big area in the middle that's the editor
Speaker 2: pain where you actually write the code. Sense Down at
Speaker 2: the bottom, you've got the debug pain super important. That's
Speaker 2: where you see print messages, check variable values. When the
Speaker 2: app is running, find.
Speaker 1: Crashes, your troubleshooting area yep.
Speaker 2: And then on the right the inspector pain. This one's
Speaker 2: context sensitive. If you're looking at code, it might show documentation.
Speaker 2: If you're designing UI, it shows all the settings and
Speaker 2: attributes for buttons, labels, whatever.
Speaker 1: So navigator, editor, debug, inspector get comfortable with those four.
Speaker 2: That's pretty much your core workflow.
Speaker 1: Yeah, okay, one quick but crucial thing before we dive
Speaker 1: into Swift itself. The bundle identifier. What is that exactly?
Speaker 2: Ah? Yeah, the bundle ID. It's basically the app's unique
Speaker 2: social security number. You could say, okay, it has to
Speaker 2: be globally unique. It's how the app store and the
Speaker 2: device itself identifies your specific app from all the millions
Speaker 2: of others.
Speaker 1: Like a web address for an app.
Speaker 2: That's a great analogy, and it usually follows that reverse
Speaker 2: domain name style like calm dot your company dot your
Speaker 2: rap name. Super important to get right right.
Speaker 1: Okay, Now into Swift itself. This is where as you said,
Speaker 1: the philosophy really shows this focus on safety and clarity,
Speaker 1: sometimes even prioritized over maybe raw speed in some micro benchmark.
Speaker 1: How does that show up right away? Just in declaring
Speaker 1: basic values.
Speaker 2: It shows up immediately with let versus var immutability, constants
Speaker 2: and variables right VARs for variables values that can change later.
Speaker 2: Let is for constant values you set once and they
Speaker 2: never change after that.
Speaker 1: And the swift way is the swift way.
Speaker 2: The strong recommendation is always use let unless you absolutely
Speaker 2: know you need to change the value later, default to immutability.
Speaker 1: Why is such a strong push for let, I mean,
Speaker 1: besides just preventing accidental changes, are there technical benefits?
Speaker 2: Oh? Definitely. Predictability is huge obviously, but also performance. When
Speaker 2: the Swift compiler sees let, it knows that piece of
Speaker 2: memory is fixed.
Speaker 1: Ah, so it can optimize.
Speaker 2: Exactly, It can store it more efficiently, maybe inline, It
Speaker 2: skip checks it might need for a variable. And for
Speaker 2: other developers reading your code, let me as a clear
Speaker 2: signal this value is stable. Don't worry about it changing unexpectedly.
Speaker 2: It's safer coding.
Speaker 1: Fundamentally, That safety focus carries right over to types, doesn't it.
Speaker 1: Swift is called statically strongly typed. Sounds kind of strict.
Speaker 1: What does that actually mean when you're coding?
Speaker 2: It means two key things. Statically typed means the compiler
Speaker 2: must know the exact type of every variable and constant.
Speaker 2: Is it an integer, a string, a custom object for
Speaker 2: the app even runs at compile time?
Speaker 1: Okay, checks happen early, right.
Speaker 2: And strongly typed means you can't play fast and loose
Speaker 2: with those types. If you declare something as a string,
Speaker 2: you can't suddenly decide to put a number and int
Speaker 2: into it.
Speaker 1: Later The compiler will just say nope.
Speaker 2: Exactly compile time error. Swift wants to catch those kinds
Speaker 2: of mistakes before they can cause crashes when a user
Speaker 2: is running the app. But hang on, if it's static,
Speaker 2: why don't I always have to write like let name
Speaker 2: string alice. Sometimes I can just write let name alice
Speaker 2: and it works. How does it know?
Speaker 1: Ah? That's the magic of type inference. Swift is clever
Speaker 1: enough in many cases to look at the value you're
Speaker 1: assigning initially and infer or deduce.
Speaker 2: The type It guess is the type.
Speaker 1: It makes an educated guess based on the value. If
Speaker 1: you write alice, it knows that's a string. If you
Speaker 1: write ten, it knows that's an int. You get the conciseness,
Speaker 1: But the key thing is the type is still figured
Speaker 1: out and locked in at compile time, it's still static
Speaker 1: and strong.
Speaker 2: Okay, that makes sense. So Swift is strict about types.
Speaker 2: That brings up a huge historical problem in programming. What
Speaker 2: about missing values, null pointers, undefined the billion dollar mistake? Right?
Speaker 2: How does Swift handle needing to represent nothing?
Speaker 1: This is one of Swift's absolute killer features. Optionals indicated
Speaker 1: by that question mark after.
Speaker 2: A type like string or int exactly.
Speaker 1: And optional is like a little box. It might contain
Speaker 1: a value of the specified type, like a string, or
Speaker 1: it might contain nil, which is Swift's way of saying
Speaker 1: no value here. And the crucial difference.
Speaker 2: Is the crucial difference is that the type system knows
Speaker 2: about the possibility of nil. A regular string cannot be nil.
Speaker 2: A string can be nil. It forces you, the developer,
Speaker 2: to explicitly deal with the possibility that the value might
Speaker 2: be missing.
Speaker 1: You can't just use it directly assuming it's there.
Speaker 2: Nope, you have to unwrap it, check if the box
Speaker 2: has something inside before you try to use it. Now
Speaker 2: you can force unwrap with an exclamation mark.
Speaker 1: Which everyone says is dangerous.
Speaker 2: It is. It's like saying, I swear this isn't nil.
Speaker 2: Trust me if you're wrong, your app crashes instantly, So yeah,
Speaker 2: avoid it unless you are absolutely positively certain.
Speaker 1: So what are the safe ways to unwrap?
Speaker 2: The main safe ways are if let and guardlet Okay,
Speaker 2: difference with if let you basically say, if this optional
Speaker 2: contains a value, let's assign it to a temporary constant
Speaker 2: and then run this block of code. That unwrapped constant
Speaker 2: is only usable inside the fin if blocks curly braces.
Speaker 1: So it's very contained, like a little safe zone exactly.
Speaker 2: Now. Guard let is often preferred, especially inside functions. It
Speaker 2: works kind of like a bouncer at a club. You
Speaker 2: use guardlet to check preconditions. At the start of a function,
Speaker 2: guard that we have a value here. If we don't.
Speaker 2: If it's nil, then we must exit immediately. The else
Speaker 2: block of a guard statement has to exit the current scope,
Speaker 2: usually with return or.
Speaker 1: Throw, So it's for checking requirements early on.
Speaker 2: Precisely, and the big advantages. If the guardlet check passes,
Speaker 2: meaning the optional did have a value, the unwrapped constant
Speaker 2: is available for use throughout the entire rest of the function,
Speaker 2: not just in a nested.
Speaker 1: Block that avoids nesting. If it's deeper and deeper, the
Speaker 1: pyramid of doom. Exactly guard let keeps your code flatter,
Speaker 1: clear and enforces that fail fast mentality. If inputs aren't valid,
Speaker 1: it's generally considered cleaner for handling requires options.
Speaker 2: That's a really clear explanation. It forces you to be
Speaker 2: honest about missing data. Okay, Moving up a level from
Speaker 2: individual values, how do we organize code into bigger chunks.
Speaker 2: We have struct and class. Big difference there, right, value
Speaker 2: versus reference types.
Speaker 1: Huge difference, probably one of the most fundamental distinctions in Swift.
Speaker 1: Let's start with structures. Struct Yeah, there are value types.
Speaker 2: Meaning when you pass a struct around, assign it to
Speaker 2: a new variable, pass it into a function, you are
Speaker 2: always working with a copy of the data. Think of
Speaker 2: it like making a photocopy.
Speaker 1: Changing the copy doesn't affect the original.
Speaker 2: Not at all. They are completely independent. Plus, structs get
Speaker 2: a handy default initializer called the member wise initializer for free,
Speaker 2: which is nice.
Speaker 1: Okay, So structs are copies. What about classes? Class?
Speaker 2: Classes are reference types. Think of this like sharing a
Speaker 2: link to a Google doc instead of emailing a word file.
Speaker 2: If you have a variable holding a class instance and
Speaker 2: you assign that to another variable, both variables now point
Speaker 2: to the exact same object in.
Speaker 1: Memory, so if one variable changes.
Speaker 2: Something, the other one sees the change immediately because they're
Speaker 2: both looking at the same underlying instance. Classes also support inheritance,
Speaker 2: which structs don't. But this shared nature brings complexity, especially
Speaker 2: with memory management, which we'll get to right.
Speaker 1: I often hear the advice prefers structs over classes that
Speaker 1: generally sound.
Speaker 2: It's a very common and generally good rule of thumb
Speaker 2: in swift development. Because value types strucks are copied, they
Speaker 2: are inherently simpler and safer. You don't have to worry
Speaker 2: about side effects some other part of your code unexpectedly
Speaker 2: changing the data out from under You use structs unless
Speaker 2: you specifically need. The shared reference behavior of classes or
Speaker 2: inheritance makes sense.
Speaker 1: Safety first again. Okay, let's shift to the visual side
Speaker 1: the UI building interfaces for iPhones iPads, the screen sizes
Speaker 1: are all over the place. You can't just say put
Speaker 1: this button a pixel X pixel y right. That old
Speaker 1: frame based layout seems impossible.
Speaker 2: Now autoly impossible. It would break immediately on a different
Speaker 2: device size or orientation. Apple solution is.
Speaker 1: Auto layout, which uses constraints exactly.
Speaker 2: Instead of giving fixed coordinates, you define rules relationships constraints
Speaker 2: between UI elements, like.
Speaker 1: This label should be eight points below that image.
Speaker 2: View precisely, or this button should be centered horizontally in
Speaker 2: its container, or these two text fields should have the
Speaker 2: same width. You define the layout using these relationships, so.
Speaker 1: You tell the system the rules, not the exact positions.
Speaker 2: You got it, and then when the screen size changes
Speaker 2: or the device rotates, the auto layout engine recalculates all
Speaker 2: the frames based on the constraints you provided. It makes
Speaker 2: adaptive layout possible. UIs that adapt gracefully to different environments.
Speaker 1: And that ties into size classes, right that compact regular widthing.
Speaker 2: Yeah. Size classes are a higher level abstraction Apple provides.
Speaker 2: They group different device sizes and orientations into categories like
Speaker 2: compact with regular height. You can then use these size
Speaker 2: classes to provide different sets of constraints or even different
Speaker 2: y or arrangements for say an iPhone in portrait versus
Speaker 2: an iPad and landscape. It adds another layer to adaptivity.
Speaker 1: Okay, this feel like we're building up the layers. We
Speaker 1: have safe data types, ways to structure code ADAPTI VII.
Speaker 1: But underlying all this, especially with classes, is memory. Things
Speaker 1: get created, They take up space. How do they get
Speaker 1: cleaned up? What's the mechanism.
Speaker 2: The mechanism is automatic reference Counting or ARC.
Speaker 1: ARC, not garbage collection like in Java.
Speaker 2: No, it's different. ARC isn't a separate process that periodically
Speaker 2: scans memory. It's more of a compile time feature where
Speaker 2: swift automatically inserts memory management code, retain and release calls
Speaker 2: into your compiled program.
Speaker 1: And it only cares about certain types.
Speaker 2: Crucially, yes, ARC only manages memory for instances of classes
Speaker 2: reference types. It doesn't need to worry about structs or
Speaker 2: enoms value types because they are copied and their memory
Speaker 2: is handled automatically when they go out of scope. It's
Speaker 2: only the shared referenced class in instances that need explicit counting.
Speaker 1: Okay, so how does this counting work? How does ARC
Speaker 1: know when it's safe to get rid of a class instance.
Speaker 2: It keeps a reference count for each class instance. When
Speaker 2: you create an instance and assign it to a variable
Speaker 2: or constant, that creates a strong reference.
Speaker 1: By default strong reference, and.
Speaker 2: That increments the instance's reference count, usually from zero to one.
Speaker 2: If you assign that same instance to another variable, the
Speaker 2: count goes up again to two.
Speaker 1: So it counts how many variables are actively pointing to it.
Speaker 2: Basically, yes, how many owners it has? You could say,
Speaker 2: as long as that reference count is greater than zero.
Speaker 2: ARC knows the instance is still needed, so it keeps
Speaker 2: it in memory.
Speaker 1: And when does it get deallocated?
Speaker 2: When the last strong reference to it is removed? Maybe
Speaker 2: a variable goes out of scope, or you explicitly set
Speaker 2: it to nil, the reference count drops when it hits zero,
Speaker 2: ARC knows nothing is using the instance anymore and immediately
Speaker 2: deallocates it, freeing up the memory.
Speaker 1: Okay, seems straightforward enough, But there's a catch, right the
Speaker 1: infamous strong retained cycle.
Speaker 2: Ah yeah, yes, the classic memory leak scenario. In reference
Speaker 2: counted systems. This happens when two or more class instances
Speaker 2: hold strong references to.
Speaker 1: Each other, like a circular dependency.
Speaker 2: Exactly. Imagine a person class that has a property for
Speaker 2: their apartment and the apartment class has a property for
Speaker 2: its tenant, the person. If both those properties are default strong.
Speaker 1: References, they're holding on to each other.
Speaker 2: Precisely, the person keeps the apartment alive reference count one,
Speaker 2: and the apartment keeps the person alive reference count one,
Speaker 2: even if nothing else in your app points to either
Speaker 2: the person or the apartment anymore. Their mutual strong references
Speaker 2: keep their counts from ever reaching.
Speaker 1: Zero, so they just stay in memory forever leaking.
Speaker 2: Yep, memory leak. ARC can't clean them up because their
Speaker 2: counts never drop to zero.
Speaker 1: Okay, so how do we break these cycles? We need
Speaker 1: a reference that doesn't increase the count, right.
Speaker 2: We need to tell AARC, hey, this link exists, but
Speaker 2: don't count it towards keeping the object alive and swift
Speaker 2: gives us two ways to do this and unowned references
Speaker 2: week and unowned.
Speaker 1: What's the difference when do you use which?
Speaker 2: The choice depends entirely on whether the reference could legitimately
Speaker 2: become nil during its lifetime. You use weak, usually written
Speaker 2: weekvar when the other instance might be deallocated before the
Speaker 2: instance holding their reference.
Speaker 1: So the reference itself needs to be able to become nil.
Speaker 2: Exactly because the thing it points to might disappear. This
Speaker 2: means weak references must always be declared as optional types
Speaker 2: like weak var delegate my delegate. The class example is
Speaker 2: a delegate pattern. A child object shouldn't keep its parent
Speaker 2: controller alive, so the reference back to the delegate is
Speaker 2: often weak.
Speaker 1: Okay, Week means it can be nil, so it must
Speaker 1: be optional. What about unowned?
Speaker 2: You use unowned when you can guarantee, absolutely guarantee that
Speaker 2: the reference will never be nil during the time you're
Speaker 2: using it. The other instance will definitely outlive or live
Speaker 2: exactly as long as the instance holding the reference.
Speaker 1: But you're making a promise to the compiler.
Speaker 2: You are because unowned references are assumed to always point
Speaker 2: to something valid, they are not optionals. Think of our
Speaker 2: person apartment example. Maybe an apartment must always have a
Speaker 2: tenant while it exists in our system, the apartment's reference
Speaker 2: back to the person could potentially be unowned.
Speaker 1: What happens if you're wrong If you use unowned and
Speaker 1: the other instance does get deallocated crash.
Speaker 2: If you try to access an unowned reference after the
Speaker 2: instance it ports too has been deallocated, your app will crash.
Speaker 2: So you use unowned for that slight performance gain. No
Speaker 2: optional unwrapping only when the relationship guarantees non n illness.
Speaker 2: Weak is generally safer. If there's any.
Speaker 1: Doubt, well, okay, that's a deep dive into memory. So
Speaker 1: summarizing the pillars, we've got language levels, safety with let
Speaker 1: var and strong typing crash prevention with optionals and safe
Speaker 1: unwrapping like guardlet structure with value types, struct and reference types,
Speaker 1: class adaptive UI with auto layout and constraints, and finally
Speaker 1: managing class memory carefully with ARC using weak or unowned
Speaker 1: to prevent retained cycles.
Speaker 2: That really covers the foundational philosophy. Getting these concepts, especially
Speaker 2: optionals in ARC, is what separates developers who write robust,
Speaker 2: stable apps from those whose apps might be prone to
Speaker 2: crashes or unexpected behavior.
Speaker 1: So, with this foundation laid, where does this lead us?
Speaker 1: For years, iOS development mostly used imperative programming for UI,
Speaker 1: right like with UIKit and patterns like MVC. We were
Speaker 1: telling the system how to change the view step by
Speaker 1: step exactly.
Speaker 2: You'd get some data, and then you'd write code to
Speaker 2: find the label on the screen and manually update its
Speaker 2: text property, find the image view and set its image,
Speaker 2: and so on, very step by step instructions.
Speaker 1: But the wind is shifting, isn't it towards something more declarative?
Speaker 2: Massively shifting the new standard Swift UI flicks the model completely.
Speaker 2: It uses declarative programming, meaning instead of telling the system
Speaker 2: how to update the UI piece by piece, you simply
Speaker 2: declare what the UI should look like for any given
Speaker 2: state of your data.
Speaker 1: So you define the end result for each state precisely.
Speaker 2: You say, the data looks like this, the screen should
Speaker 2: look like that, and you do this for all possible states.
Speaker 2: Swift UI then figures out the most efficient way to
Speaker 2: transition between those states automatically when the data changes. You
Speaker 2: don't manage the individual updates anymore.
Speaker 1: That sounds like a fundamental paradigm shift less manual control.
Speaker 1: More describing the outcome.
Speaker 2: It absolutely is. And understanding the imperative world of UIKit
Speaker 2: and the principles we discussed today, especially type safety, value types,
Speaker 2: and immutability, actually provides the perfect grounding to appreciate why
Speaker 2: the declarative approach of swift UI is so powerful and efficient.
Speaker 2: It builds directly on those core swift philosophies.
Speaker 1: So a provocative thought for listeners. Yeah, master these fundamentals
Speaker 1: the imperative way things were done, because it prepares you
Speaker 1: perfectly for the declarative way things are going. Explore youikit,
Speaker 1: understand arc and then get ready for swift UI.
Speaker 2: Couldn't have sent it better myself. That's the journey.
Speaker 1: Excellent. A lot to digest there, but absolutely crucial knowledge
Speaker 1: that wraps up this deep dive