Chapter 2: Variables and Constants

*In Swift, you can optionally use underscored to make larger numbers more human-readable. The quantity and placement of the underscores is up to you.

*Swift is very strict about the types it uses and won't let you assign a value of one type to a variable of another type. Instead of simply assigning, you need to explicitly say that you want to convert the type.

var integer: Int = 100

var decimal: Double = 12.5

integer = Int(decimal)

 

*A tuple is a type that represents data composed of more than one value of any type.

If you want to ignore a certain element of the tuple, you can replace the corresponding part of the declaration with an underscore. 

let (x2, y2, _) = coordinates3D

*Sometimes it's useful to check the inferred type of a variable or constant. You can do this in a playground by holding down the Option key and clicking on the variable or constant's name.

*Type inference allows you to omit the type when Swift already knows it.