【Swift 60秒】09 - Arrays

0x00 Lesson

Arrays are collections of values that are stored as a single value. For example, John, Paul, George, and Ringo are names, but arrays let you group them in a single value called The Beatles.
In code, we write this:

let john = "John Lennon"
let paul = "Paul McCartney"
let george =  "George Harrison"
let ringo = "Ringo Starr"
let beatles = [john, paul, george, ringo]
1
2
3
4
5

That last line makes the array: it starts and ends with brackets, with each item in the array separated by a comma.

You can read values from an array by writing a number inside brackets. Array positions count from 0, so if you want to read “Paul McCartney” you would write this:

beatles[1]
1

Be careful:
Swift crashes if you read an item that doesn’t exist. For example, trying to read beatles[9] is a bad idea.

Note:
If vou’re using type annotations, arrays are written in brackets: [String], [Int], [Double] and [Bool]

---

0x01 Tips

If your array is empty, even reading array[0] will cause your app to crash. Be careful!

---

0x02 Test

Which of these lines create arrays?

01

let status = false, true, true, false
1

02

let characters: [Int] = ["Doctor Who"]
1

03

let playlistSizes = (100, 200, 300)
1

04

let height = "14.0"
1

05

let age = 26
1

06

let breeds = {"Labrador", "Chihuahua"}
1

07

var scores: [Int] = [12,23,24]
1

Answer:
01 - false: Arrays start and end with square brackets.
02 - false: This attempts to place a string array into an integer array, which is invalid in Swift.
03 - false: Arrays start and end with square brackets, [ and ], rather than parentheses.
04 - false: This creates s string.
05 - false: This creates an integer.
06 - false: Arrays start and end with square brackets, [ and ], rather than braces.
07 - true: This creates an array of three integers.

---

0x03 我的小作品

欢迎体验我的作品之一：小五笔 86 版
五笔学习好帮手
App Store 搜索即可~

---