【Swift】配列の要素を検索してインデックスを取得する方法！first/firstIndex

array.first

let language = ["HTML","CSS","JavaScript","PHP","Swift"]

if let lang = language.first {
    print(lang) // HTML
}

Cannot call value of non-function type 'String?

let language = ["HTML","CSS","JavaScript","PHP","Swift"]
if let lang = language.first(where: { $0 == "HTML" }) {
    print(lang) // HTML
}

let numbers = [3, 5, -12, 43, -4, 10]
if let firstNum = numbers.first(where: { $0 > 4 }) {
    print(firstNum) // 5
}

let firstNum = numbers.first {
    $0 > 4
}
print(firstNum) // 5

let language = ["HTML","CSS","JavaScript","PHP","Swift"]
if let lang = language.first(where: { $0.contains("wif")}) {
    print(lang) // Swift
}

array.firstIndex(of:)

let language = ["HTML","CSS","JavaScript","PHP","Swift"]
if let index = language.firstIndex(of: "Swift") {
    print(index) // 4
}

let language = ["HTML","CSS","JavaScript","PHP","Swift"]
if let index = language.firstIndex(where: {$0.hasPrefix("S")}) {
    print(index) // 4
}

let language = ["HTML":5,"CSS":3,"JavaScript":1,"PHP":8,"Swift":5]
if let lang = language.first {
    print(lang.key) // Swift
    print(lang.value) // 5
}

// 2回目
// JavaScript
// 1

let array = ["A","B","C"]
print(array[3])

error: Execution was interrupted, reason: EXC_BREAKPOINT (code=1, subcode=0x18bcdc794).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.

print(array[safe: 3] ?? 0)