在Swift 4.2中构建CSV字符串的灵活代码

import Foundation

func buildCSVString(data: [[String]]) -> String {
    var csvString = ""
    
    for row in data {
        var rowString = ""
        
        for (index, value) in row.enumerated() {
            let escapedValue = value.replacingOccurrences(of: "\"", with: "\"\"")
            let field = "\"\(escapedValue)\""
            
            if index != row.count - 1 {
                rowString += "\(field),"
            } else {
                rowString += "\(field)\n"
            }
        }
        
        csvString += rowString
    }
    
    return csvString
}

let data = [["Name", "Age", "City"],
            ["John Doe", "25", "New York"],
            ["Jane Smith", "30", "San Francisco"],
            ["Bob Johnson", "35", "Chicago"]]

let csvString = buildCSVString(data: data)
print(csvString)

"Name","Age","City"
"John Doe","25","New York"
"Jane Smith","30","San Francisco"
"Bob Johnson","35","Chicago"