教程复制自https://iostutorialjunction.com/2018/01/create-csv-file-in-swift-programmatically.html：
步骤1：

创建一个名为“employeeArray”的数组，它将把所有雇员的记录作为键值对象存储起来。

class ViewController: UIViewController {
 var employeeArray:[Dictionary<String, AnyObject>] =  Array()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
   for i in 1...10 {
            var dct = Dictionary<String, AnyObject>()
            dct.updateValue(i as AnyObject, forKey: "EmpID")
            dct.updateValue("NameForEmplyee id = \(i)" as AnyObject, forKey: "EmpName")
            employeeArray.append(dct)
        }
    }
}

第2步：现在我们有了数据，是时候使用swift编程创建CSV（逗号分隔值）文件了。为此，我们将遍历“employeeArray”中的记录，并将它们添加到一个字符串中。然后，我们将把这个字符串写入应用程序的文档目录中。所有的东西都放在名为“createCSV”的不同函数中，下面是相同的代码

func createCSV(from recArray:[Dictionary<String, AnyObject>]) {
        var csvString = "\("Employee ID"),\("Employee Name")\n\n"
        for dct in recArray {
            csvString = csvString.appending("\(String(describing: dct["EmpID"]!)) ,\(String(describing: dct["EmpName"]!))\n")
        }
        
        let fileManager = FileManager.default
        do {
            let path = try fileManager.url(for: .documentDirectory, in: .allDomainsMask, appropriateFor: nil, create: false)
            let fileURL = path.appendingPathComponent("CSVRec.csv")
            try csvString.write(to: fileURL, atomically: true, encoding: .utf8)
        } catch {
            print("error creating file")
        }

    }

步骤3：最后我们将从“viewDidLoad”调用函数。

class ViewController: UIViewController {
 var employeeArray:[Dictionary<String, AnyObject>] =  Array()
    
    override func viewDidLoad() {
        super.viewDidLoad()
         for i in 1...10 {
                   var dct = Dictionary<String, AnyObject>()
                   dct.updateValue(i as AnyObject, forKey: "EmpID")
                   dct.updateValue("NameForEmplyee id = \(i)" as AnyObject, forKey: "EmpName")
                   employeeArray.append(dct)
               }

               createCSV(from: employeeArray)

    }
 
 func createCSV(from recArray:[Dictionary<String, AnyObject>]) {
        var csvString = "\("Employee ID"),\("Employee Name")\n\n"
        for dct in recArray {
            csvString = csvString.appending("\(String(describing: dct["EmpID"]!)) ,\(String(describing: dct["EmpName"]!))\n")
        }
        
        let fileManager = FileManager.default
        do {
            let path = try fileManager.url(for: .documentDirectory, in: .allDomainsMask, appropriateFor: nil, create: false)
            let fileURL = path.appendingPathComponent("CSVRec.csv")
            try csvString.write(to: fileURL, atomically: true, encoding: .utf8)
        } catch {
            print("error creating file")
        }

    }
 }

上面的回答很好，做了一个小的修改来处理数据中的特定示例。你可以根据需要修改单个组件，删除逗号，修剪UUID等。注意，这个解决方案使用存储在Core Data对象列表中的事务。我还打印了数据文件的位置，这样你就可以在模拟器中检查它。

func createCSVFile() {
        var csvString = "id,name,description,category,date,type,receipt,amount\n"
        for trans in transactions {
            let transID = trans.id!.debugDescription.split(separator: "-")[0].replacingOccurrences(of: ")", with: "")
            let transName = trans.name!
            let transDesc = trans.desc!.replacingOccurrences(of: ",", with: "-")
            let transCat = trans.category!
            let transDate = trans.date!
            let transType = trans.type!
            
            var transReceipt = "None"
            if trans.receipt == nil {
                transReceipt = "Present"
            }
            let transAmount = trans.amount
            let dataString = "\(transID),\(transName),\(transDesc),\(transCat),\(transDate),\(transType),\(transReceipt),\(transAmount)\n"
            print("DATA: \(dataString)")
            csvString = csvString.appending(dataString)
        }

        let fileManager = FileManager.default
        do {
            let path = try fileManager.url(for: .documentDirectory, in: .allDomainsMask, appropriateFor: nil, create: false)
            print("PATH: \(path)")
            let fileURL = path.appendingPathComponent("CSVData.csv")
            try csvString.write(to: fileURL, atomically: true, encoding: .utf8)
        } catch {
            print("error creating file")
        }
    }