我需要从一个文本文件读取和写入数据，但我还没有弄清楚怎么做。
我在Swift的iBook中找到了这个示例代码，但我仍然不知道如何写入或读取数据。
import Cocoa
class DataImporter {
/*
DataImporter is a class to import data from an external file.
The class is assumed to take a non-trivial amount of time to initialize.
*/
var fileName = "data.txt"
// the DataImporter class would provide data importing functionality here
}
class DataManager {
@lazy var importer = DataImporter()
var data = String[]()
// the DataManager class would provide data management functionality here
}
let manager = DataManager()
manager.data += "Some data"
manager.data += "Some more data"
// the DataImporter instance for the importer property has not yet been created”
println(manager.importer.fileName)
// the DataImporter instance for the importer property has now been created
// prints "data.txt”
var str = "Hello World in Swift Language."
func writeToDocumentsFile(fileName:String,value:String) {
let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
let path = documentsPath.appendingPathComponent(fileName)
do{
try value.write(toFile: path, atomically: true, encoding: String.Encoding.utf8)
}catch{
}
}
func readFromDocumentsFile(fileName:String) -> String {
let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
let path = documentsPath.appendingPathComponent(fileName)
let checkValidation = FileManager.default
var file:String
if checkValidation.fileExists(atPath: path) {
do{
try file = NSString(contentsOfFile: path, encoding: String.Encoding.utf8.rawValue) as String
}catch{
file = ""
}
} else {
file = ""
}
return file
}
目前从亚当上面接受的答案对我来说有一些错误，但这是我如何重做他的答案，使这个工作对我来说。
let file = "file.txt"
let dirs: [String]? = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true) as? [String]
if (dirs != nil) {
let directories:[String] = dirs!
let dirs = directories[0]; //documents directory
let path = dirs.stringByAppendingPathComponent(file);
let text = "some text"
//writing
text.writeToFile(path, atomically: false, encoding: NSUTF8StringEncoding, error: nil);
//reading
var error:NSError?
//reading
let text2 = String(contentsOfFile: path, encoding:NSUTF8StringEncoding, error: &error)
if let theError = error {
print("\(theError.localizedDescription)")
}
}
斯威夫特3。X - 5.x
最好的例子是创建一个扩展名为.txt的本地日志文件
可以在“文件应用程序”中显示当前日期和时间作为文件名
只需在信息中添加此代码。请启用这两个功能
UIFileSharingEnabled
LSSupportsOpeningDocumentsInPlace
和下面的函数
var logfileName : String = ""
func getTodayString() -> String{
let date = Date()
let calender = Calendar.current
let components = calender.dateComponents([.year,.month,.day,.hour,.minute,.second], from: date)
let year = components.year
let month = components.month
let day = components.day
let hour = components.hour
let minute = components.minute
let second = components.second
let today_string = String(year!) + "-" + String(month!) + "-" + String(day!) + "-" + String(hour!) + "" + String(minute!) + "" + String(second!)+".txt"
return today_string
}
func LogCreator(){
logfileName = getTodayString()
print("LogCreator: Logfile Generated Named: \(logfileName)")
let file = logfileName //this is the file. we will write to and read from it
let text = "some text" //just a text
if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
let fileURL = dir.appendingPathComponent(file)
let documentPath = NSSearchPathForDirectoriesInDomains(.documentDirectory,.userDomainMask, true)[0]
print("LogCreator: The Logs are Stored at location \(documentPath)")
//writing
do {
try text.write(to: fileURL, atomically: false, encoding: .utf8)
}
catch {/* error handling here */}
//reading
do {
let text2 = try String(contentsOf: fileURL, encoding: .utf8)
print("LogCreator: The Detail log are :-\(text2)")
}
catch {/* error handling here */}
}
}
[1]: https://i.stack.imgur.com/4eg12.png
早期的解决方案回答了问题，但在我的情况下，删除文件的旧内容而写入是一个问题。
所以，我创建了一段代码写入文件目录中的文件，而不删除以前的内容。您可能需要更好的错误处理，但我相信这是一个很好的起点。斯威夫特4。
Usuage:
let filename = "test.txt"
createOrOverwriteEmptyFileInDocuments(filename: filename)
if let handle = getHandleForFileInDocuments(filename: filename) {
writeString(string: "aaa", fileHandle: handle)
writeString(string: "bbb", fileHandle: handle)
writeString(string: "\n", fileHandle: handle)
writeString(string: "ccc", fileHandle: handle)
}
辅助方法:
func createOrOverwriteEmptyFileInDocuments(filename: String){
guard let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else {
debugPrint("ERROR IN createOrOverwriteEmptyFileInDocuments")
return
}
let fileURL = dir.appendingPathComponent(filename)
do {
try "".write(to: fileURL, atomically: true, encoding: .utf8)
}
catch {
debugPrint("ERROR WRITING STRING: " + error.localizedDescription)
}
debugPrint("FILE CREATED: " + fileURL.absoluteString)
}
private func writeString(string: String, fileHandle: FileHandle){
let data = string.data(using: String.Encoding.utf8)
guard let dataU = data else {
debugPrint("ERROR WRITING STRING: " + string)
return
}
fileHandle.seekToEndOfFile()
fileHandle.write(dataU)
}
private func getHandleForFileInDocuments(filename: String)->FileHandle?{
guard let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else {
debugPrint("ERROR OPENING FILE")
return nil
}
let fileURL = dir.appendingPathComponent(filename)
do {
let fileHandle: FileHandle? = try FileHandle(forWritingTo: fileURL)
return fileHandle
}
catch {
debugPrint("ERROR OPENING FILE: " + error.localizedDescription)
return nil
}
}
对于读写，您应该使用一个可写的位置，例如文档目录。下面的代码展示了如何读写一个简单的字符串。你可以在操场上测试。
斯威夫特3。X - 5.x
let file = "file.txt" //this is the file. we will write to and read from it
let text = "some text" //just a text
if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
let fileURL = dir.appendingPathComponent(file)
//writing
do {
try text.write(to: fileURL, atomically: false, encoding: .utf8)
}
catch {/* error handling here */}
//reading
do {
let text2 = try String(contentsOf: fileURL, encoding: .utf8)
}
catch {/* error handling here */}
}
斯威夫特2.2
let file = "file.txt" //this is the file. we will write to and read from it
let text = "some text" //just a text
if let dir = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true).first {
let path = NSURL(fileURLWithPath: dir).URLByAppendingPathComponent(file)
//writing
do {
try text.writeToURL(path, atomically: false, encoding: NSUTF8StringEncoding)
}
catch {/* error handling here */}
//reading
do {
let text2 = try NSString(contentsOfURL: path, encoding: NSUTF8StringEncoding)
}
catch {/* error handling here */}
}
快1.倍
let file = "file.txt"
if let dirs : [String] = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true) as? [String] {
let dir = dirs[0] //documents directory
let path = dir.stringByAppendingPathComponent(file);
let text = "some text"
//writing
text.writeToFile(path, atomically: false, encoding: NSUTF8StringEncoding, error: nil);
//reading
let text2 = String(contentsOfFile: path, encoding: NSUTF8StringEncoding, error: nil)
}
