Array

概念

• 数组是有序数据的集。
• 集合是无序、无重复数据的集。
• 字典是无序的键值对的集。

Array

• 初始化固定长度数组

  let b = Array(repeating: 0, count: 10000);
  print(b); // [0, 0, ...]
  

• 初始化特定类型的空数组

  let b: [String] = [];
  print(b); // []
  

拼接

• 必须要同类型才能拼接

let a: [Double] = [1, 2, 3, 4, 5, 6, 7]

let b = [8.0, 9.0];
print(a + b); // [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0]

count

let a: [Double] = [1, 2, 3, 4, 5, 6, 7]
print(a.count); // 7

相等

• 可以用==或elementsEqual判断两个数组的元素和顺序相等

var a = [1, 2, 3, 4, 5, 6, 7]
var b = [1, 2, 3, 4, 5, 6, 7]

print(a == b) // true
print(a.elementsEqual(b)) // true

增删改查

contains

• 单值包含

  var a = [1, 2, 3, 4, 5, 6, 7]
  
  let b = a.contains(3)
  print(b); // true
  

• 复杂条件包含

  var a = [1, 2, 3, 4, 5, 6, 7]
  
  let b = a.contains(where: {$0 > 8})
  print(b); // false
  

starts

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.starts(with: [1, 2, 3])

print(b); // true

first

• 第一个符合计算函数的值

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.first(where: {$0 > 2}) ?? -1
print(b); // 3

last

• 最后一个符合计算函数的值

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.last(where: {$0 < 5}) ?? -1
print(b); // 4

lastIndex

• 最后一个匹配下标

var a = [1, 2, 3, 4, 5, 6, 3]

let b = a.lastIndex(of: 3) ?? -1
print(b); // 6

firstIndex

• 第一个匹配下标

var a = [1, 2, 3, 4, 5, 6, 3]

let b = a.firstIndex(of: 3) ?? -1
print(b); // 2

append

var a: [Double] = [1, 2, 3, 4, 5, 6, 7]
a.append(8)
print(a); // [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0]

同

var a: [Double] = [1, 2, 3, 4, 5, 6, 7]
a += [8]
print(a); // [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0]

区间替换

• 单个字符替换

  var a = [1, 2, 3, 4, 5, 6, 7]
  a[3] = 10
  print(a); // [1, 2, 3, 10, 5, 6, 7]
  

• 区间替换(相当于JS的splice)，删除指定位数并插入数组

  var a = [1, 2, 3, 4, 5, 6, 7]
  a[3...4] = [10, 11, 199]
  print(a); // [1, 2, 3, 10, 11, 199, 6, 7]
  

replaceSubrange

• 写法没有区间替换写法简洁

var a = [1, 2, 3, 4, 5, 6, 7]

a.replaceSubrange(0...2, with: [0, 0])
print(a); // [0, 0, 4, 5, 6, 7]

swapAt

• 两个元素换位置

var a = [1, 2, 3, 4, 5, 6, 7]

a.swapAt(2, 3)

print(a); // [1, 2, 4, 3, 5, 6, 7]

partition

• 查询不满足给定条件的数量

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.partition(by: {$0 > 1})

print(b); // 1

insert

• 单个字符插入

  var a = [1, 2, 3, 4, 5, 6, 7]
  a.insert(100, at: 3)
  print(a); // [1, 2, 3, 100, 4, 5, 6, 7]
  

• 多个字符插入

  var a = [1, 2, 3, 4, 5, 6, 7]
  a.insert(contentsOf: [100, 101], at: 3)
  print(a); // [1, 2, 3, 100, 101, 4, 5, 6, 7]
  

• 头部插入

  var a = [1, 2, 3, 4, 5, 6, 7]
  a.insert(0, at: 0)
  print(a); // [0, 1, 2, 3, 4, 5, 6, 7]
  

remove

• 移除指定下标项

var a = [1, 2, 3, 4, 5, 6, 7]
a.remove(at: 3)
print(a); // [1, 2, 3, 5, 6, 7]

removeSubrange

• 移除下标区间

var a = [1, 2, 3, 4, 5, 6, 7]
a.removeSubrange(1...3)
print(a); // [1, 5, 6, 7]

removeAll

var a = [1, 2, 3, 4, 5, 6, 7]
a.removeAll(where: {$0 < 3})
print(a); // [3, 4, 5, 6, 7]

removeLast

• 移除最后一个

var a = [1, 2, 3, 4, 5, 6, 7]
a.removeLast()
print(a); // [1, 2, 3, 4, 5, 6]

removeFirst

• 移除第一个

var a = [1, 2, 3, 4, 5, 6, 7]
a.removeFirst()
print(a); // [2, 3, 4, 5, 6, 7]

suffix

• 获取末尾固定位数的新数组

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.suffix(3)

print(b); // [5, 6, 7]

遍历

for-in

var a = [1, 2, 3, 4, 5, 6, 7]

for i in a {
  print(i); // 1234567
}

enumerated

• 转化成区间[(idx, val)...]

var a = [1, 2, 3]

for (idx, val) in a.enumerated() {
  print("index是\(idx), value 是\(val)")
}

//index是0, value 是1
//index是1, value 是2
//index是2, value 是3

indices

var a = [1, 2, 3, 4, 5, 6, 7]

for idx in a.indices {
    print(idx); // 0123456
}

forEach

var a = [1, 2, 3, 4, 5, 6, 7]

a.forEach({print($0)}) // 1234567

反向遍历

var a = [1, 2, 3, 4, 5, 6, 7]
a.reversed().forEach({print($0)}); // 7654321

var a = [1, 2, 3, 4, 5, 6, 7]

for i in a.reversed() {
    print(i); // 7654321
}

其他操作

sort

• 传入函数返回值确定 $0是否在前面
• 不改变原数组

var a = [1, 6, 3, 4, 2, 5]

let b = Array(a.sorted(by: {$0 < $1}))
print(b); // [1, 2, 3, 4, 5, 6]

filter

• 不改变原数组

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.filter({$0 % 2 != 0})
print(b); // [1, 3, 5, 7]

map

• 不改变原数组

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.map({$0 % 2 == 0 ? "偶" : "奇"})
print(b); // ["奇", "偶", "奇", "偶", "奇", "偶", "奇"]

reduce

• 不改变原数组
• 参数与js相反，$0初始值，$1计算函数

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.reduce(100, {$0 + $1})
print(b); // 128

compactMap

• 与map用法相同，但是返回的一定是非空项，否则就剔除掉

var a = [1, 2, 3, 4, 5, 6, 3]

let b = a.compactMap({$0 > 3 ? $0 : nil})
print(b); // [4, 5, 6]

compactMap

• map + flat功能

var a = [1, 2, 3, 4, 5, 6]

let b = a.flatMap({Array(repeating: $0, count: $0)})
print(b); // [1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6]

reversed

• 逆转后只是用的原数组引用，如果要生成新数组要用Array

var a = [1, 2, 3, 4, 5, 6]

let b = Array(a.reversed())
print(b); // [6, 5, 4, 3, 2, 1]

max

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.max()!
print(b); // 7

min

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.min()!
print(b); // 1

prefix

• 相当于获取区间，得到subSequence

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.prefix(3)
let c = a[0...2]

print(b); // [1, 2, 3]
print(c); // [1, 2, 3]

randomElement

• 随机获取数组的一个元素

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.randomElement()!

print(b); // 1

shuffled

• 洗牌函数

var a = [1, 2, 3, 4, 5, 6, 7]

let b = a.shuffled()

print(b); // [5, 3, 2, 4, 6, 7, 1]