swift: working with string

Question

We have a simple string:

let str = "\"abc\", \"def\",\"ghi\" , 123.4, 567, \"qwe,rty\""

If we do this:

let parsedCSV = str
            .components(separatedBy: .newlines)
            .filter { !$0.isEmpty }
            .map { $0.components(separatedBy: ",") }
            .map { $0.map { $0.trimmingCharacters(in: .whitespaces) } }
print(parsedCSV)

we get this:

[["\"abc\"", "\"def\"", "\"ghi\"", "123.4", "567", "\"qwe", "rty\""]]

Is there a simple solution (using functional programming) not to split the last element \"qwe,rty\", because we know that it's one whole thing?

That's not so simple. You need context to handle the " and in general it's easier to just go loop by the columns one by one. — Sulthan
– Sulthan, Commented Jun 28, 2018 at 14:43
I would recommend to use a library, e.g. github.com/naoty/SwiftCSV — Sulthan
– Sulthan, Commented Jun 28, 2018 at 14:45
Non-trivial CSV data is a lot more complicated to process than most people realize. It can't be parsed with simple string manipulations. Use (or write) a proper CSV parsing library. — rmaddy
– rmaddy, Commented Jun 28, 2018 at 15:53

Nour · Accepted Answer · 2018-06-28 22:33:24Z

1

Well this is a hack, it works for this case.... not very simple solution for complex issue ...

let str = "\"abc\", \"def\",\"ghi\" , 123.4, 567, \"qwe,rty\""

let parsedCSV = str
    .components(separatedBy: .newlines)
    .filter { !$0.isEmpty }
    .map { $0.components(separatedBy: ",") }
    .map { $0.map { $0.trimmingCharacters(in: .whitespaces) } }.reduce([]) { (result, items) -> [String] in
        var goodItems = items.filter{ $0.components(separatedBy: "\"").count == 3 ||  $0.components(separatedBy: "\"").count == 1}
        let arr = items.filter{ $0.components(separatedBy: "\"").count == 2}
        var join:[String] = []
        for x in 0..<arr.count {
            let j = x + 1
            if j < arr.count {
                join = [arr[x] + "," + arr[j]]
            }
        }
        goodItems.append(contentsOf: join)
        return goodItems
}


print(parsedCSV)

print out

["\"abc\"", "\"def\"", "\"ghi\"", "123.4", "567", "\"qwe,rty\""]

answered Jun 28, 2018 at 22:33

Nour

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1 Comment

Anton Over a year ago

Yes, that's the way it should be! Still it's not perfect, because if we add something at the end of the str - the order of the output string will be changed.

Anton · Accepted Answer · 2018-06-30 12:19:29Z

I've done that.

let str = "_, * ,, \"abc\",  000, def, ghi , 123.4,,  567,  \"qwe,rty,eur\", jkl"
    let separator = ","
    let parsedCSV = str
        .components(separatedBy: .newlines)
        .filter { !$0.isEmpty }
        .map { $0.components(separatedBy: separator).map { $0.trimmingCharacters(in: .whitespaces) } }
        .reduce([]) { (result, items) -> [String] in
            var result: [String] = []
            for item in items {
                guard let last = result.last, last.components(separatedBy: "\"").count % 2 == 0 else {
                    result.append(item)
                    continue
                }
                result.removeLast()
                let lastModified = record + separator + item
                result.append(lastModified)

            }
            return result
    }.map { $0.trimmingCharacters(in: CharacterSet(charactersIn: "\"")) }
    print(parsedCSV)

["_", "*", "", "abc", "000", "def", "ghi", "123.4", "", "567", "qwe,rty,eur", "jkl"]

OOPer · Accepted Answer · 2018-06-30 14:43:49Z

If you do not mind using Regular Expression, you can write something like this:

let str = "_, * ,, \"abc\",  000, def, ghi , 123.4,,  567,  \"qwe,rty,eur\", jkl"

let pattern = "((?:[^\",]|\"[^\"]*\")*)(?:,|$)"
let regex = try! NSRegularExpression(pattern: pattern)

let parsedCSV = regex.matches(in: str, options: .anchored, range: NSRange(0..<str.utf16.count))
    .map {$0.range(at: 1)}
    .filter {$0.location != NSNotFound && $0.location < str.utf16.count}
    .map {String(str[Range<String.Index>($0, in: str)!]).trimmingCharacters(in: .whitespaces)}
    .map {$0.trimmingCharacters(in: CharacterSet(charactersIn: "\""))}
print(parsedCSV) //->["_", "*", "", "abc", "000", "def", "ghi", "123.4", "", "567", "qwe,rty,eur", "jkl"]

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