does swift 4 need a main class to run or not ? and when should i use a class to run my code?

Question

import Foundation

func diagonalDifference(arr: [[Int]]) -> Int {



}

let stdout = ProcessInfo.processInfo.environment["OUTPUT_PATH"]!
FileManager.default.createFile(atPath: stdout, contents: nil, attributes: nil)
let fileHandle = FileHandle(forWritingAtPath: stdout)!

guard let n = Int((readLine()?.trimmingCharacters(in: .whitespacesAndNewlines))!)
else { fatalError("Bad input") }

let arr: [[Int]] = AnyIterator{ readLine() }.prefix(n).map {
    let arrRow: [Int] = $0.split(separator: " ").map {
        if let arrItem = Int($0.trimmingCharacters(in: .whitespacesAndNewlines)) {
            return arrItem
        } else { fatalError("Bad input") }
    }

    guard arrRow.count == n else { fatalError("Bad input") }

    return arrRow
}

guard arr.count == n else { fatalError("Bad input") }

let result = diagonalDifference(arr: arr)

fileHandle.write(String(result).data(using: .utf8)!)
fileHandle.write("\n".data(using: .utf8)!)

I just want to know ,is there any main function in swift like java which run first? and How should i scan a line or int in swift through console?

to scan input from console you can use `readLine` https://developer.apple.com/documentation/swift/1641199-readline — G. Veronika, Sep 03 '18 at 05:51
If your code is working, then clearly a main class is not needed. If it's not working, what problems do you experience? — Cristik, Sep 03 '18 at 06:01
Maybe [this](https://www.raywenderlich.com/511-command-line-programs-on-macos-tutorial) article could be useful — Joakim Danielson, Sep 03 '18 at 06:04

score 1 · Accepted Answer · answered Sep 03 '18 at 05:54

1

Example of readLine usage to scan console input (the function from the Swift Standard Library)

let userInput = readLine()

It returns an optional value (String?)

answered Sep 03 '18 at 05:54

G. Veronika

232
2
11

does swift 4 need a main class to run or not ? and when should i use a class to run my code?

1 Answers1