- Swift_集合 let inde = arr.firstInd
- Swift_集合 let inde = arr.firstInd
- Swift_集合 let inde = numbers.part
- Swift_集合 let shuffledArr = numbe
- 8.集合类型(CollectionType)
- Swift_集合 let arrSub = arr.prefix
- Swift_集合 ` let arrSub = arr.pref
- Swift_集合 let element = arr.`remo
- Swift_集合 let arrSub = arr.`dro
- Swift_集合 ` let arrSub = arr.suff
let inde = arr.firstIndex(of element: Element)
-> Int?
let streets = ["Adams", "Bryant", "Channing", "Douglas", "Evarts"]
let inde = streets.firstIndex(of: "Evarts") // 4
let streetsSlice = streets[2...]
// ["Channing", "Douglas", "Evarts"]
let inde0 = streetsSlice.firstIndex(of: "Evarts") // 4
let inde1 = streetsSlice.firstIndex(of: "aa") // nil
print(inde0 as Any)
print(inde1 as Any)
// Log inde0 == 4
// Log inde1 == nil
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