Swift笔记（一）

发布时间：2020-12-14 01:29:20 所属栏目：百科来源：网络整理

导读：我的主力博客：半亩方塘 1、In Swift,you can optionally use underscores to make larger numbers more human-readable. The quantity and placement of the underscores is up to you. var variableNumber: Int = 1_000_000 2、 var integer: Int = 100var

我的主力博客：半亩方塘

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

var variableNumber: Int = 1_000_000

2、

var integer: Int = 100
var decimal: Double = 12.5
integer = decimal  // wrong
integer = Int(decimal)   // right

3、Here is how to access the data inside the tuple:

let coordinates: (Int,Int) = (2,3)  
let x: Int = coordinates.0  
let y: Int = coordinates.1

You can reference each item in the tuple by its position in the tuple,starting with zero. Swift allows you to name the individual parts of a tuple,so you to be explicit about what each part represents. For example:

let coordinatesNamed: (x: Int,y: Int) = (2,3)  
let x: Int = coordinatesNamed.x
let y: Int = coordinatesNamed.y

If you want to access multiple parts of the tuple at the same time,you can also use a shorthand syntax to make it easier:

let coordinates3D: (x: Int,y: Int,z: Int) = (2,3,1)
let (x,y,z) = coordinates3D

The code is equivalent to the following:

let coordinates3D: (x: Int,1)
let x = coordinates3D.x
let y = coordinates3D.y
let z = coordinates3D.z

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

let (x,_) = coordinates3D

This line of code only declaresxandy. The_is special and simply means you are ignoring this part for now. You'll find that you can use the underscore throughout Swift to ignore a value.

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

（编辑：李大同）

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