如何在 swift 5 的文档目录中编写新行 CSV 文件?

Question

我有一个函数，如果它不存在，我想创建一个CSV文件并向其中添加数据。如果它确实存在，我想在每次调用时将此数据添加为新行。

这是我当前的代码，目前它每次都覆盖整个文件：

func writeTrackedSymptomValues(symptom: String, comment: String, time: String, timestamp: String) {
symptomData = SymptomData()
for _ in 0..<5 {
symptomData.symptom = symptom
symptomData.severity = self.severity
symptomData.comment = comment
symptomData.timestamp = timestamp
symptom_data.append(symptomData!)
}
creatCSV()
}
func creatCSV() -> Void {
let fileName = "symptom_data.csv"
let path = self.getDocumentsDirectory().appendingPathComponent(fileName)
var csvText = "Symptom,Severity,Comment,Timen"

let newLine = "(symptomData.symptom),(symptomData.severity),(symptomData.comment),(symptomData.timestamp)n"
csvText.append(newLine)

do {
try csvText.write(to: path, atomically: true, encoding: String.Encoding.utf8)
} catch {
print("Failed to create file")
print("(error)")
}
print(path ?? "not found")
}
func getDocumentsDirectory() -> URL {
// find all possible documents directories for this user
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
// just send back the first one, which ought to be the only one
return paths[0]
}

如何每次都添加新行？swift

Answer 1

使用Warren的建议解决：

var logFile: URL? {
guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return nil }
let fileName = "symptom_data.csv"
return documentsDirectory.appendingPathComponent(fileName)
}

此函数检查文件是否存在，如果不存在，则像我最初的问题一样，如果是，则使用 FileManager 添加新行。

func createCSV() {
guard let logFile = logFile else {
return
}
guard let data = ("(symptomData.symptom),(symptomData.severity),(symptomData.comment),(symptomData.timestamp)n").data(using: String.Encoding.utf8) else { return }
if FileManager.default.fileExists(atPath: logFile.path) {
if let fileHandle = try? FileHandle(forWritingTo: logFile) {
fileHandle.seekToEndOfFile()
fileHandle.write(data)
fileHandle.closeFile()
}
} else {
var csvText = "Symptom,Severity,Comment,Timen"

let newLine = "(symptomData.symptom),(symptomData.severity),(symptomData.comment),(symptomData.timestamp)n"
csvText.append(newLine)

do {
try csvText.write(to: logFile, atomically: true, encoding: String.Encoding.utf8)
} catch {
print("Failed to create file")
print("(error)")
}
print(logFile ?? "not found")
}
}