數組（Arrays）是有序數據的集,元素可重復；
遵守Array<Element>類型，Element是這個數組中唯一允許存在的數據類型;
也可以用簡單的形式表示:[Element]

1.定義

//空數組
var tempArr = Array<String>() //也可以
var arr = [String]()
//字面量賦值
var arr1 : [String] = ["a","b","c"]
var arr2 = ["a","b","c","d"]

var arr3 = Array(repeating: "0", count: 5)

2.數組是否為空

/*
var arr = [String]()
if arr.isEmpty {
    print("arr is empty")
}
//arr is empty
*/

3.數組的長度：count

4.數組的訪問：下標法

var arr2 = ["a","b","c","d"]
print(arr2[2])  //c

5.增

var arr2 = ["a","b","c","d"]
var arr3 = arr2
//增加單個元素
arr2.append("f")
//增加數組
arr2 += ["1","2"]
print(arr2) // ["a", "b", "c", "d", "f", "1", "2"]

arr3.insert("_", at: 0)
print(arr3) // ["_", "a", "b", "c", "d"]

6.刪

//tempArr.removeAll() //清空全部數組
//tempArr.removeLast() //刪除第一個元素
//tempArr.removeFirst()//刪除第一個元素
//tempArr.removeFirst(n: Int) param:n: Int代表第幾個元素；n = 1，表示刪除tempArr[0]

 var arr2 = ["a","b","c","d"]
 arr2.remove(at: 1)
 print(a)   // ["a", "c", "d"]

7.改

var arr2 = ["a","b","c","d"]
//當個元素
arr2[0] = "1"
print(arr2) //["1", "b", "c", "d"]
//多個元素
arr2[1...2] = ["2","3"]
print(arr2) //["1", "2", "3", "d"]

8.數組的遍歷

//forin 遍歷 :獲取元素
    var arr2 = ["a","b","c","d"]
    for item in arr2 {
        print(item)
    }
//a
//b
//c
//d

//enumerated()遍歷，獲取每個數據項的值和索引值
    var arr2 = ["a","b","c","d"]
    for (index,value) in arr2.enumerated() {
        print("Item \(String(index)): \(value)")
    }
//Item 0: a
//Item 1: b
//Item 2: c
//Item 3: d