Module 3 of 3 in Your First iOS App: An App From Scratch

Your First iOS App: Coding in Swift

Jul 28 2026, Swift 6.3, iOS 26, Xcode 26
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Learn core Swift language features while building and testing Bull’s Eye app logic. You will use the Swift Standard Library, write unit tests, practice test-driven development, control program flow with if/else statements, and work with variables, constants, and type inference. By Catie Catterwaul.

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EXPERIENCE
Beginner level
EST TIME TO COMPLETE
39 mins
CONTENT
8 lessons
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Module outcomes

  • Use Swift Standard Library functionality while building app logic.
  • Validate Swift code with unit tests and test-driven development.
  • Control program flow and model values with if/else statements, variables, constants, and type inference.

Covered concepts

  • Swift Standard Library
  • Unit testing
  • Test-driven development
  • If/else statements
  • Variables, constants & type inference

Module content

1
The Swift Standard Library Lesson (5 mins)

Learn about the pre-built data types and functions you can use in your apps to solve a variety of common tasks.

 Start
Introduction • Start Video · 1 min
The Swift Standard Library Video · 5 mins
2
Intro to Unit Testing Lesson (8 mins)

Learn how you can add unit tests to your app to automatically verify your app works the way you expect.

 Start
Intro to Unit Testing • Start Video · 8 mins
3
Intro to Test-Driven Development Lesson (4 mins)

Learn how you can use test-driven development to write tests for your code before you write the code itself and why this can be beneficial to you.

 Start
Intro to Test-Driven Development • Start Video · 4 mins
4
Challenge: How to Calculate the Difference Lesson (3 mins)

See if you can figure out an algorithm to calculate the positive difference between the target value and the slider value.

 Start
Challenge: How to Calculate the Difference • Start Video · 3 mins
5
If Else Statements Lesson (4 mins)

Learn how to write if/else statements in Swift and how you can use them to implement the algorithm.

 Start
If Else Statements • Start Video · 4 mins
6
Challenge: Calculate the Difference Lesson (2 mins)

Try improving the algorithm to calculate the difference so it is written in fewer lines of code.

 Start
Challenge: Calculate the Difference • Start Video · 2 mins
7
Variables & Constants Lesson (5 mins)

Finalize the difference algorithm and score calculation, and learn about an important Swift concept: the difference between variables and constants.

 Start
Variables & Constants • Start Video · 5 mins
8
Type Inference Lesson (8 mins)

Learn how Swift infers types from context and when explicit types are useful.

 Start
Type Inference • Start Video · 5 mins
Conclusion Reading · 3 mins
Quiz: Coding in Swift 6 questions