What you'll build
- A program to calculate the circumference of a circle.
What you'll learn
- How types are used to distinguish different kinds of values, and that every value used in a program has a type.
- How Swift makes sure types are used correctly.
- How Swift will try to infer the type of values.
Key vocabulary
Introduction
Everything around you is a type of something. People divide things into types, or classifications, based on commonly understood features and capabilities. You know what a pencil is, what you can do with it, and when you might want to use a pencil rather than a pen. In this lesson, you’ll learn that the values in your programs also fall into classifications that affect what they can do and what you might want to use them for.
Go Build
Open the Types.playground file in your course resources and follow the instructions.
Reflection Questions
Think of a single screen of an app you use. How many different types of information do you think are involved?
Can you think of other types beyond strings and numbers?
How would you write a program that deals with a music collection?
What types might you need?
Summary
Careful use of types will make your programs easier to understand and easier to write. Swift contains protections to notify you if you’re using types incorrectly.
You also added to your list of kinds of expressions. Now you know that expressions either can be literal values or can use a combination of mathematical operators.
You’ve now scratched the surface of the vast range of types available to you in the Swift standard library and the Foundation framework. As you progress through more lessons, you’ll get to know more types and you’ll also create your own.
