Basic usage of Swift (one of Swift development)

Last night, Apple released the next-generation programming language Swift, which provides an iBook instruction document. You can refer to it if you need it. Https://itunes.apple.com/cn/book/swift-programming-language/id881256329? Mt = 11


Next, let me talk about some basic things. Everyone is just reading them, so I will inevitably encounter errors in understanding them. Welcome to note. Of course, you can also directly read the official documentation.


I. Basic Types of let and var

Let: constant. values cannot be assigned twice. You do not need to specify the type when assigning values. The Compiler automatically determines Based on the assignment. You can also manually specify the type.
Var: Variable

Let a = 12 // declare a as constant 12, type Intlet B: Double = 12 // declare a as constant 12, manually specify the type Double

Ii. String

1. the plus sign can be directly spliced into strings, and Other types cannot be directly spliced into strings.
 

let str = "Hello, playground. "let name = "Tom "let count = 10let say = str + name + String(count)  // "Hello, playground. Tom 10"

2. Directly introduce code into strings

let a = 1let b = 2let say = "the number is \(a + b)"  // "the number is 3"

3. arrays and dictionaries can be directly declared using []

1. Array

Var arr = ["catfish", "water", "tulips ", "blue paint"] arr [1] = "bottle of water" // modify the second arr // ["catfish", "bottle of water", "tulips ", "blue paint"]

2. Dictionary

Var man = ["like": "apple", "name": "Tom",] man ["iphone"] = "5s" // Add the man ["like"] = "mac" // modify the man field // ["iphone ": "5 s", "like": "mac", "name": "Tom"]

Iv. control statements

1. if cannot directly use a variable or constant as a condition. It must be a judgment statement.

let a = 12if a > 0 {    // do something} else {   // do something}

If you write it as if a {}, an error is returned. You cannot directly use variables or constants to determine bool.


2.

For I in 0 .. 3 {/I = 0, 1, 2} for var I = 0; I <3; ++ I {/I = 0, 1, 2} // array let scores = [1, 2, 3, 4, 5] for score in scores {// score} // dictionary let numsDic = ["": [2, 3, 5, 7, 11, 13], "B": [1, 1, 2, 3, 5, 8], "c": [1, 4, 9, 16, 25],] for (key, numbers) in numsDic {for number in numbers {// number }}

3. while

var n = 2while n < 100 {    n = n * 2}var m = 2do {    m = m * 2} while m < 100