//배열

입력값                                                                                                    출력값

[1, 2, 3, 4]                                                                                                                [1, 2, 3, 4]

["가", "나", "다"]                                                                                                     ["가", "나", "다"]     

var intArray = [1, 2, 3, 4]                                                                                         [1, 2, 3, 4]

var stringArray = ["가", "나", "다"]                                                                           ["가", "나", "다"]

만일

var emptyArray = [ ] 라고 입력하면 어떻게 될까요?

오류가 납니다.

이유는 입력값의 자료가 무엇인지 알 수 없기 때문입니다.

이럴 경우

var emptyArrayA:[Int] =[ ]                                                                                     [ ]

var empytArrayB = [Int]( )                                                                                     [ ]

var emptyArrayC:[String] = [ ]                                                                               [ ]

var emptyArrayD = [String]( )                                                                                [ ]

var emptyArrayE:[Float] = [ ]                                                                                 [ ]

var emptyArrayF = [Float]( )                                                                                  [ ]

위의 6개의 출력값은 모두 동일합니다.

다시 처음으로 돌아가서

var intArray = [1, 2, 3, 4]                                                                                         [1, 2, 3, 4]

var stringArray = ["가", "나", "다"]                                                                        ["가", "나", "다"]

intArray[0]                                                                                                               1

intArray[1]                                                                                                               2

intArray[2]                                                                                                               3

intArray[3]                                                                                                               4

배열에서 시작은 0, 1, 2, 3 ....... 순으로 시작합니다.

이 0, 1, 2, 3 ......으로 시작하는 숫자를 index라고 합니다.

0부터 시작한다고 해서 제로인덱스(0 index)라고 합니다.

그럼 아래처럼

intArray[4]                                                                                                              error

를 입력하게되면, 출력값에 에러를 표기하게 됩니다.

(이때 생성되는 오류 이름이   Index out of range가 됩니다)

stringArray[0]                                                                                                      "가"

stringArray[1]                                                                                                      "나"

stringArray[2]                                                                                                      "다"

만일 element의 갯수를 알고 싶다면

intArray.count                                                                                                      4

stringArray.count                                                                                                 3

위처럼 써 주면 몇 개인지 보여줍니다.