Introduction to Swift

Hi and welcome back! 0:00 Now that you have Xcode installed, it's time to start coding in Swift. 0:01 In this video, I'll introduce you to the fundamentals of Swift, including 0:06 how to write basic code, use variables, and work with common data types. 0:10 These building blocks will set you up for success as we move 0:15 towards creating your very first app by the end of this workshop. 0:18 Let's jump in! 0:23 To get started, let's open Xcode. 0:25 Instead of creating a full app project, we'll use a playground, 0:29 a space where you can quickly write and test Swift code. 0:33 To create one, go to the top left and click 0:37 File, New, Playground. 0:40 When prompted to choose a template, select macOS Blank. 0:43 This is the simplest option and perfect for practicing Swift. 0:48 Next, name your file whatever you'd . 0:52 I'll name mine Swift-Basics and save it in my Swift folder. 0:55 But you can save yours anywhere that's convenient. 1:00 Once your 1:04 playground is set up, you'll see a window with three panels. 1:04 The left panel is a navigator. 1:08 Since we won't be using it in this workshop, 1:10 you can hide it by clicking this icon. 1:13 The right panel is where we'll see the output of our code as it runs. 1:16 We'll explore this in action soon. 1:20 The center panel is where we'll be writing our Swift code. 1:23 This is where the magic happens. 1:27 When you open your Playground, Xcode provides some sample code to start with. 1:29 The first line imports the Cocoa framework, which includes 1:34 libraries and APIs for macOS app development. 1:38 Since we won't be using it in this workshop, we can safely delete that line. 1:42 Now let's focus on the second line. 1:47 var greeting equals hello Playground. 1:49 here's what's happening var is a keyword that creates a variable 1:52 which is a named storage for data that can change 1:57 greeting is the name of our variable 2:01 and it's set to the string hello comma playground 2:04 which is a sequence of text in close in quotation marks 2:08 variables are a fundamental part 2:12 of programming so let's explore that further in swift 2:15 you use var to declare variables and let to declare constants. 2:19 Here's an example. 2:24 I'll create a variable called name and set it equal to my name, Laura. 2:26 Then I'll create a constant named color and set it to red. 2:31 Now let run our code Click the play button next to the line number 2:36 and Xcode will execute everything up to that point 2:40 The first time you run it it may take a moment but once it finished 2:44 you see the values of our variable and constant displayed in the right panel 2:48 So what's the difference between var and let? 2:53 Variables declared with var can have their values changed later. 2:57 Constants declared with let cannot be changed once they're assigned a value. 3:02 Let me show you this in action. 3:08 I'll update the name variable's value 3:10 to Chris by writing name equals Chris. 3:13 Notice that I didn't use var again. 3:18 That's because you only use var or let 3:20 when declaring a variable or constant for the first time. 3:23 After that, you can simply update the value for variables. 3:27 Now let's run our code. 3:31 In the right panel, you'll see that the name variable's value 3:33 has updated to Chris. 3:37 But what happens if we try to change the value of a constant? 3:39 Let's test it out. 3:43 I'll attempt to change color to blue. 3:45 After a moment, we get an error. 3:48 Cannot assign to value. 3:50 Color is a let constant. 3:52 This means Swift won't let us reassign a new value to color 3:55 because it was declared as a constant using let. 3:59 Constants are useful when you want to ensure 4:03 a value remains unchanged throughout your program. 4:05 To fix this, let's delete the line that tries to change color 4:09 and the error will disappear. 4:13 Swift is a type 4:16 safe language, which means that once a variable has been assigned a type, 4:17 it cannot change to another type. 4:22 Let's test this by trying to assign a number to our name variable. 4:25 I'll attempt to set name to 42. 4:30 Right away, we get an error. 4:34 Cannot assign value of type int, 4:36 which stands for integer, to type string. 4:39 This tells us that name was originally declared as a string, 4:43 so it can only store text, not numbers. 4:47 In Swift, once a variable has a type, 4:50 it must always hold values of that same type. 4:53 Let's delete this line to remove the error. 4:57 Swift supports many data types, but in this introductory workshop, 5:01 we'll focus only on the ones we'll be using for our Dice Roller app. 5:06 The first type, 5:11 which we've been using from the start, is the string type. 5:12 Strings are used for text and are enclosed in quotation marks 5:16 Another data type we briefly saw is integers which represent 5:21 whole numbers Let create a variable that stores an integer 5:25 var myAge equals 30 5:30 Unlike strings you don need quotation marks when assigning an integer. 5:34 Now that we know how to store data in variables, what can we do with it? 5:38 One useful thing we can do is print values 5:43 to the console using the print function. 5:46 The print function allows us to send messages 5:49 to the console which appears at the bottom of the screen. 5:51 Let's try printing a message. 5:55 Inside of this print statement, let's write a string, my name is. 5:58 We can even print a variable. 6:03 Now let's run the file and check the console. 6:06 We see two messages, my name is and Laura. 6:10 The first message comes from the string we wrote inside the print function, 6:15 and the second message comes from our name variable. 6:20 Swift recognizes the variable, 6:24 retrieves its stored value, and prints it to the console. 6:26 Printing is a great way to check values 6:30 and debug your code as you write it. 6:32 Let's experiment by switching the order of our print statements. 6:36 I'll use Command X to cut the first print statement 6:40 and Command V to paste it below the second one. 6:43 Programming is all about experimenting 6:48 and seeing what happens, so don't be afraid to play around. 6:51 All great programmers do. 6:54 Now let's run the code. 6:56 As expected, the message appears in the new order. 6:58 That's because in Swift and most programming languages, 7:01 code runs from top to bottom, 7:05 executing each line in sequence. 7:08 The first print statement runs first, followed by the next, and so on. 7:11 What if 7:16 we wanted both messages to appear on the same line? 7:17 Instead of using two separate print statements, 7:20 we can combine them using string interpolation. 7:23 String interpolation allows us to insert variables inside 7:27 a string by using a backslash followed by parentheses. 7:31 Let's also have the message display our age. 7:37 And I am backslash open parentheses 7:40 my age years old. 7:43 Now if we delete the previous 7:47 print statement and run the code, we see 7:48 my name is Laura and I am 30 years old. 7:51 Everything is printed on a single line. 7:55 String interpolation makes code more dynamic 7:58 and readable For example if we update our variables 8:01 we can reassign the name variable to John 8:06 and set his age to 12 8:09 and run the code again Now we see 8:13 my name is John and I am 12 years old. 8:16 This shows how powerful variables are. 8:20 They allow us to write flexible, reusable code. 8:23 The last topic I want to cover 8:27 is a key feature for our Dice app, generating random numbers. 8:29 When you roll a standard die, you get a number between 1 8:34 and 6, and you never know what the number will come up. 8:37 It's random. 8:41 Similarly, in coding, when you need a random number, 8:42 you can tell Swift the range, for example 1 to 6, 8:45 and Swift will randomly select the number for you. 8:49 In Swift, this is done using the following code. 8:53 Let dice roll equals int dot random 8:57 in 1 dot dot dot 6. 9:01 Let's break it down. 9:05 Int specifies that we want a whole number, an integer. 9:06 Dot random in tells Swift, give me a random number. 9:10 1 dot dot dot 6 defines the range. 9:15 It tells Swift, choose a number between 1 9:19 and 6, including both 1 and 6. 9:22 Let dice roll 9:27 stores a random number in a constant, so we can use it later. 9:28 Without storing it, we wouldn't be able to reference it in our program. 9:32 Now let's say you're making a board game app and need to simulate rolling two dice. 9:37 You could write let first dice equal 9:42 int dot random in 1 dot dot dot 6. 9:46 Then copy it, paste it, 9:52 and we'll rename this one to second dice. 9:55 Then have a print statement that says you rolled 10:00 a backslash first dice 10:04 and a backslash second dice. 10:08 If we run the code, we see 10:12 you rolled a 5 and a 1. 10:15 If we run it again, we should see different results 10:19 each time, just rolling real dice. 10:22 Great work! 10:27 You've now learned 10:27 some key Swift fundamentals that we'll use when building our Dice Roller app. 10:28 You now know how to work with variables and constants, 10:33 use string interpolation, and generate random numbers. 10:37 In the next video, I'll give you a tour of SwiftUI. 10:41 I'll see you there. 10:44

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