Swift3.0基础知识笔记

五月 20, 2019

import UIKit

字典的读取和编辑

var message_me = ["11":"亦可","12":"小艾","13":"李可"]
print(message_me)
print(message_me["11"]!)//使用下标语法通过键获得相应的值
message_me["14"] = "亦可"//使用下标语法添加新元素
print(message_me)
message_me["12"] = "李毅"//使用下标语法修改对应元素值
print(message_me)
message_me.updateValue("舒儿", forKey: "15")//使用updateValue()方法，修改指定键的值
print(message_me)
message_me["12"] = nil //将某个键的值设为nil,删除对应的键值对
print(message_me)
message_me.removeValue(forKey: "11")//使用removeValue(forKey: "  ")方法删除指定的键值对
print(message_me)

字典的遍历

for key_a in message_me.keys //遍历键
    {

print(key_a)

}
for value_b in message_me.values//遍历值
{

print(value_b)

for (key,value) in message_me//遍历键值对

print(key+”:”+value)

}
let num=2
switch num {
case 1:

数组

数组遍历
var numbers = [1,1,12,3,4,56,78,45]

for index in 0..<numbers.count
 {

print(numbers[index])

}
for number in numbers
{
print(number)
}
numbers+=[23,45,56]//数组拼接用+号
numbers.append(100)//数组在末尾加一个数
numbers.insert(200, at: 3)//在指定位置插入一个数
numbers[1]=1000//改变数组的某个值

numbers.isEmpty//判断数组是否为空

numbers.count//计算数组的长度

numbers.contains(200)//判断是否存在200
numbers.sort()//数组排序，默认升序排列

numbers.sort(by:>)//降序排列

var userList = [(name:”Tom”,age:20),(name:”Alise”,age:19),(name:”Aike”,age:20)]

userList.sort(by:{$0.name>$1.name})//复杂元素进行排序

case 2:

复杂数组遍历

let scores = ["jerry":78,"Tom":89,"Aili":94]
for (name,score) in scores
{
print(name + "score is \(score)")
}

对维数组遍历

  let Scores = [[1,4,567,43],[35,67,89,34],[23,56,67,54]]
  for subScore in Scores
  {
  for Score in subScore
  {
      print(Score)

}
  }

对指定范围数组遍历使用定义range的方法实现
```
let number_r = [1,2,3,4,5,6]
  let range = 2..<number_r.count
 for (index_i,value) in zip(range, number_r[range])//zip()的作用是将两个序列的元素，一一对应合并生成一个新序列。
 {
 print("\(index_i):\(value)")
 }
```
default:
```
print("输入错误！")
```
}
//continue语句,跳过此次循环
let studentSex = [“man”,”woman”,”man”,”woman”,”man”,”woman”,”man”,”woman”]
var boysAcount = 0
for sex in studentSex
{
```
if(sex=="woman")//注意等号（==）与赋值号（=）
{
continue
}
```
boysAcount+=1
}
print(boysAcount)

//fallthrough语句，继续下一个case分支，swift默认只执行选择的case分支
let time = 6
var message = “It’s now”
switch time {
case 2,3,4,5,6,7,9,10,16:
```
message+=" \(time) o'clock"
fallthrough
```
default:
```
message+=" ."
```
}
switch语句：把一个值与若干值匹配，执行匹配到的语句

let Time = 12
switch Time {
case 7:
```
print("It's Time get up!")
```
case 8,12,18:
```
print("It's Time for eating!")
```
case let x where x>18 && x<=24:
```
print("It's Time for happy!")
```
case 1…6:
print(“It’s Time for rest!”)
default:
```
print("Keep busy!")
```
}
if条件判断语句：
let IDcard = “530381199705202956”
let count = IDcard.lengthOfBytes(using: String.Encoding.utf8)
if count == 18
{
```
print("准确的身份证号")
```
}
else if count == 15
{
```
print("准确的身份证号")
```
}
else
{
```
print("不准确的身份证号")
```
}
repeat-while语句：与传统的do-whilet语句一样：先执行语句块在，判断，至少执行一次
var Index = 0
repeat
{
```
Index += 1
print("你好，love！")
```
}while Index < 5
while循环语句
var index = 0
while index < 5 {
```
index += 1
print("你好，like!")
```
}

for循环：

重复一条语句达到特定的条件

for _ in 0..<3//（..<)表示0~3，但不包含3,(_)表示一个占位符
{
    print("黑凤梨！")
}

for _ in 0...3//（...）表示0~3，包含3
{
print("Love you!")
}

字符串的比较

let passwordFromUser = "w2956m"
  let passwordFromDb = "w2956m"
  if passwordFromUser == passwordFromDb
  {
    print("你可以登录系统！")

}

字符串的大小写转换

let hello = "Hello WangMeng!"
  print(hello.uppercased())//转换为大写
  print(hello.lowercased())//转换为小写
  print(hello.capitalized)//转换为首字母大写

字符串的截取和替换

var hello_s = "遇见未知的自己！"
  hello_s.replacingOccurrences(of: "遇见", with: "找寻")
  hello_s.remove(at: hello_s.index(hello_s.startIndex, offsetBy: 3))

浮点数据的实用函数

let number_f = -9.8
  number_f.advanced(by: 20) //加上20
  number_f.distance(to: 23.3)//获得两个数据的差值
  number_f.isFinite//判断数据是否有限
  number_f.isInfinite//判断数据是否无限
  number_f.isZero//判断数据是否为零
  number_f.isLess(than: -9.0)//判断数据是否小于-9.0
  number_f.isNaN//判断数据是否为空
  number_f.isEqual(to: -9.80)//判断数据是否等于-9.80
  number_f.isNormal //判断数据是否正常

三元条件运算符question ？answer1 ：answer2

let score = 66
  let result=(score>60) ? "通过考试":"未通过考试" //注意（？）号前后都有一个空格

元组值得访问

let http404Error = (statusCOde:404,description:"not found!")
  print("访问此页面时出现\(http404Error.statusCOde),页面\(http404Error.description)")

1. 字典的读取和编辑
2. 数组
3. for循环：