Very simple CSV reader in Swift; probably not suitable for very large files

CSVReader.swift

//
//  CSVReader.swift
//
//  Created by Michael Rockhold on 2/15/19.
//  Copyright © 2019 Michael Rockhold. All rights reserved.
//

import Foundation

struct CSVReader: Sequence  {
    
    func makeIterator() -> CSVReaderIterator {
        return CSVReaderIterator(self)
    }
    
    struct CSVReaderIterator: IteratorProtocol {
        var csvReader: CSVReader
        init(_ r:CSVReader) {
            csvReader = r
        }
        
        mutating func next() -> [String]? {
            repeat {
                if let row = csvReader.rowIterator.next() {
                    let tuple = row.split(separator: ",", maxSplits: 32, omittingEmptySubsequences: false).map { String($0) }
                    if !(tuple.count == 1 && tuple[0] == "") {
                        return tuple
                    }
                } else {
                    return nil
                }
            } while true
        }
    }
    
    let data: String
    var rowIterator: IndexingIterator<[String.SubSequence]>
    
    init?(filename:String) {
        do {
            data = try String(contentsOfFile: filename)
            let rows = data.split(separator: "\n", omittingEmptySubsequences: false)
            rowIterator = rows.makeIterator()
        } catch {
            return nil
        }
    }
}

You might call this with something like:

let data50 = "data/data50.csv"

for row in CSVReader(filename: data50)! {
    let (articleId, wordId, count) = (row[0],row[1],row[2])
    print(articleId, wordId, count)
}