从文本文件读取和写入字符串

我需要向/从文本文件读取数据或将数据写入文本文件，但我一直无法弄清楚该怎么做。

我在Swift的iBook中找到了此示例代码，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."

为了进行读写，您应该使用可写的位置，例如documents目录。以下代码显示了如何读写简单的字符串。您可以在操场上进行测试。

雨燕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 */}
}

斯威夫特1.x

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)
}

假设您已将文本文件data.txt移至Xcode项目（使用拖放并选中“如有必要，请复制文件”），就可以像在Objective-C中那样进行以下操作：

let bundle = NSBundle.mainBundle()
let path = bundle.pathForResource("data", ofType: "txt")        
let content = NSString.stringWithContentsOfFile(path) as String

println(content) // prints the content of data.txt

更新：
要从Bundle（iOS）中读取文件，可以使用：

let path = NSBundle.mainBundle().pathForResource("FileName", ofType: "txt")
var text = String(contentsOfFile: path!, encoding: NSUTF8StringEncoding, error: nil)!
println(text)

Swift 3更新：

let path = Bundle.main.path(forResource: "data", ofType: "txt") // file path for file "data.txt"
var text = String(contentsOfFile: path!, encoding: NSUTF8StringEncoding, error: nil)!

对于Swift 5

let path = Bundle.main.path(forResource: "ListAlertJson", ofType: "txt") // file path for file "data.txt"
let string = try String(contentsOfFile: path!, encoding: String.Encoding.utf8)

Xcode 8.x•Swift 3.x或更高版本

do {
    // get the documents folder url
    if let documentDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
        // create the destination url for the text file to be saved
        let fileURL = documentDirectory.appendingPathComponent("file.txt")
        // define the string/text to be saved
        let text = "Hello World !!!"
        // writing to disk 
        // Note: if you set atomically to true it will overwrite the file if it exists without a warning
        try text.write(to: fileURL, atomically: false, encoding: .utf8)
        print("saving was successful")
        // any posterior code goes here
        // reading from disk
        let savedText = try String(contentsOf: fileURL)
        print("savedText:", savedText)   // "Hello World !!!\n"
    }
} catch {
    print("error:", error)
}

新的更简单和推荐的方法： Apple建议使用URL进行文件处理，此处似乎不建议使用其他解决方案（请参阅下面的评论）。以下是使用URL进行读取和写入的新的简单方法（请不要忘记处理可能的URL错误）：

Swift 5 +，4和3.1

import Foundation  // Needed for those pasting into Playground

let fileName = "Test"
let dir = try? FileManager.default.url(for: .documentDirectory, 
      in: .userDomainMask, appropriateFor: nil, create: true)

// If the directory was found, we write a file to it and read it back
if let fileURL = dir?.appendingPathComponent(fileName).appendingPathExtension("txt") {

    // Write to the file named Test
    let outString = "Write this text to the file"
    do {
        try outString.write(to: fileURL, atomically: true, encoding: .utf8)
    } catch {
        print("Failed writing to URL: \(fileURL), Error: " + error.localizedDescription)
    }

    // Then reading it back from the file
    var inString = ""
    do {
        inString = try String(contentsOf: fileURL)
    } catch {
        print("Failed reading from URL: \(fileURL), Error: " + error.localizedDescription)
    }
    print("Read from the file: \(inString)")
}

Xcode 8，Swift 3从应用程序包读取文件的方式：

if let path = Bundle.main.path(forResource: filename, ofType: nil) {
    do {
        let text = try String(contentsOfFile: path, encoding: String.Encoding.utf8)
        print(text)
    } catch {
        printError("Failed to read text from \(filename)")
    }
} else {
    printError("Failed to load file from app bundle \(filename)")
} 

这是一个方便的复制和粘贴扩展

public extension String {
    func contentsOrBlank()->String {
        if let path = Bundle.main.path(forResource:self , ofType: nil) {
            do {
                let text = try String(contentsOfFile:path, encoding: String.Encoding.utf8)
                return text
                } catch { print("Failed to read text from bundle file \(self)") }
        } else { print("Failed to load file from bundle \(self)") }
        return ""
    }
    }

例如

let t = "yourFile.txt".contentsOrBlank()

您几乎总是需要一系列行：

let r:[String] = "yourFile.txt"
     .contentsOrBlank()
     .characters
     .split(separator: "\n", omittingEmptySubsequences:ignore)
     .map(String.init)

我只想向您展示第一部分，即已阅读。这是您可以轻松阅读的内容：

斯威夫特3：

let s = try String(contentsOfFile: Bundle.main.path(forResource: "myFile", ofType: "txt")!)

斯威夫特2：

let s = try! String(contentsOfFile: NSBundle.mainBundle().pathForResource("myFile", ofType: "txt")!)

在Swift> 4.0中读取文件的最简单方法

 let path = Bundle.main.path(forResource: "data", ofType: "txt") // file path for file "data.txt"
        do {
            var text = try String(contentsOfFile: path!)
        }
        catch(_){print("error")}
    }

上面来自亚当的当前公认答案对我来说有一些错误，但是这就是我重新设计他的答案并为我完成这项工作的方式。

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)")
    }
}

您可能会发现此工具不仅对在Swift中读取文件有用，而且还可以解析您的输入：https：//github.com/shoumikhin/StreamScanner

只需指定文件路径和数据定界符，如下所示：

import StreamScanner

if let input = NSFileHandle(forReadingAtPath: "/file/path")
{
    let scanner = StreamScanner(source: input, delimiters: NSCharacterSet(charactersInString: ":\n"))  //separate data by colons and newlines

    while let field: String = scanner.read()
    {
        //use field
    }
}

希望这可以帮助。

我不得不这样重新编码：

let path = NSBundle.mainBundle().pathForResource("Output_5", ofType: "xml")
let text = try? NSString(contentsOfFile: path! as String, encoding: NSUTF8StringEncoding)
print(text)

在函数示例中，具有一些函数包装器的（read | write）DocumentsFromFile（...）似乎很有意义，因为OSx和iOS中的所有内容似乎都需要实例化三个或四个主要类，并配置，链接，实例化并设置，仅在182个国家/地区中将“ Hi”写入文件即可。

但是，这些示例还不够完整，无法在实际程序中使用。写入功能不会报告创建或写入文件的任何错误。在读取时，我认为最好返回一个错误消息，指出该文件不存在，因为该字符串应该包含已读取的数据。您可能想知道它失败了，以及为什么要通过某种通知机制，例如异常。然后，您可以编写一些代码来输出问题所在，并允许用户纠正问题，或者“正确”地中断程序。

您不希望只返回其中包含“错误文件不存在”的字符串。然后，您将不得不每次从调用函数中查找字符串中的错误并在那里进行处理。您也可能无法真正确定错误字符串是从实际文件中实际读取的，还是从代码中产生的。

您甚至无法在swift 2.2和Xcode 7.3中调用这样的read，因为NSString（contentsOfFile ...）会引发异常。如果您没有任何代码可以捕获它并对其执行任何操作，例如将其打印到stdout，或者更好地是一个错误弹出窗口或stderr，则这是编译时错误。我听说苹果公司正在远离尝试捕获和异常，但是这将是一个漫长的步伐，如果没有这一点，就不可能编写代码。我不知道＆error参数来自哪里，也许是一个较旧的版本，但是NSString.writeTo [File | URL]当前没有NSError参数。它们在NSString.h中定义如下：

public func writeToURL(url: NSURL, atomically useAuxiliaryFile: Bool, encoding enc: UInt) throws
public func writeToFile(path: String, atomically useAuxiliaryFile: Bool, encoding enc: UInt) throws
public convenience init(contentsOfURL url: NSURL, encoding enc: UInt) throws
public convenience init(contentsOfFile path: String, encoding enc: UInt) throws

同样，不存在的文件只是程序读取文件时可能会遇到的许多潜在问题之一，例如权限问题，文件大小或您甚至不想尝试为处理程序编写代码的许多其他问题。他们每个人。最好只是假设一切都正确并捕获并打印或处理异常情况（如果出现问题），此外，在这一点上，您实际上还没有选择。

这是我的改写：

func writeToDocumentsFile(fileName:String,value:String) {

    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString!
    let path = documentsPath.stringByAppendingPathComponent(fileName)

    do {
        try value.writeToFile(path, atomically: true, encoding: NSUTF8StringEncoding)
    } catch let error as NSError {
        print("ERROR : writing to file \(path) : \(error.localizedDescription)")
    }

}

func readFromDocumentsFile(fileName:String) -> String {

    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
    let path = documentsPath.stringByAppendingPathComponent(fileName)

    var readText : String = ""

    do {
        try readText = NSString(contentsOfFile: path, encoding: NSUTF8StringEncoding) as String
    }
    catch let error as NSError {
        print("ERROR : reading from file \(fileName) : \(error.localizedDescription)")
    }
    return readText
}

对于我的txt文件，这种工作方式是：

let myFileURL = NSBundle.mainBundle().URLForResource("listacomuni", withExtension: "txt")!
let myText = try! String(contentsOfURL: myFileURL, encoding: NSISOLatin1StringEncoding)
print(String(myText))

为避免混淆和增加便利性，我创建了两个函数，用于在文档目录中的文件中读取和写入字符串。功能如下：

func writeToDocumentsFile(fileName:String,value:String) {
    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as! NSString
    let path = documentsPath.stringByAppendingPathComponent(fileName)
    var error:NSError?
    value.writeToFile(path, atomically: true, encoding: NSUTF8StringEncoding, error: &error)
}

func readFromDocumentsFile(fileName:String) -> String {
    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as! NSString
    let path = documentsPath.stringByAppendingPathComponent(fileName)
    var checkValidation = NSFileManager.defaultManager()
    var error:NSError?
    var file:String

    if checkValidation.fileExistsAtPath(path) {
        file = NSString(contentsOfFile: path, encoding: NSUTF8StringEncoding, error: nil) as! String
    } else {
        file = "*ERROR* \(fileName) does not exist."
    }

    return file
}

这是它们的用法示例：

writeToDocumentsFile("MyText.txt","Hello world!")

let value = readFromDocumentsFile("MyText.txt")
println(value)  //Would output 'Hello world!'

let otherValue = readFromDocumentsFile("SomeText.txt")
println(otherValue)  //Would output '*ERROR* SomeText.txt does not exist.'

希望这可以帮助！

Xcode版本：6.3.2

最新的swift3代码
您可以使用以下代码从文本文件中读取数据这是我的文本文件

     {
"NumberOfSlices": "8",
"NrScenes": "5",
"Scenes": [{
           "dataType": "label1",
           "image":"http://is3.mzstatic.com/image/thumb/Purple19/v4/6e/81/31/6e8131cf-2092-3cd3-534c-28e129897ca9/mzl.syvaewyp.png/53x53bb-85.png",

           "value": "Hello",
           "color": "(UIColor.red)"
           }, {
           "dataType": "label2",
           "image":"http://is1.mzstatic.com/image/thumb/Purple71/v4/6c/4c/c1/6c4cc1bc-8f94-7b13-f3aa-84c41443caf3/mzl.hcqvmrix.png/53x53bb-85.png",
           "value": "Hi There",
           "color": "(UIColor.blue)"
           }, {
           "dataType": "label3",
           "image":"http://is1.mzstatic.com/image/thumb/Purple71/v4/6c/4c/c1/6c4cc1bc-8f94-7b13-f3aa-84c41443caf3/mzl.hcqvmrix.png/53x53bb-85.png",

           "value": "hi how r u ",
           "color": "(UIColor.green)"
           }, {
           "dataType": "label4",
           "image":"http://is1.mzstatic.com/image/thumb/Purple71/v4/6c/4c/c1/6c4cc1bc-8f94-7b13-f3aa-84c41443caf3/mzl.hcqvmrix.png/53x53bb-85.png",
           "value": "what are u doing  ",
           "color": "(UIColor.purple)"
           }, {
           "dataType": "label5",
          "image":"http://is1.mzstatic.com/image/thumb/Purple71/v4/6c/4c/c1/6c4cc1bc-8f94-7b13-f3aa-84c41443caf3/mzl.hcqvmrix.png/53x53bb-85.png",
           "value": "how many times ",
           "color": "(UIColor.white)"
           }, {
           "dataType": "label6",
           "image":"http://is1.mzstatic.com/image/thumb/Purple71/v4/5a/f3/06/5af306b0-7cac-1808-f440-bab7a0d18ec0/mzl.towjvmpm.png/53x53bb-85.png",
           "value": "hi how r u ",
           "color": "(UIColor.blue)"
           }, {
           "dataType": "label7",
           "image":"http://is5.mzstatic.com/image/thumb/Purple71/v4/a8/dc/eb/a8dceb29-6daf-ca0f-d037-df9f34cdc476/mzl.ukhhsxik.png/53x53bb-85.png",
           "value": "hi how r u ",
           "color": "(UIColor.gry)"
           }, {
           "dataType": "label8",
           "image":"http://is2.mzstatic.com/image/thumb/Purple71/v4/15/23/e0/1523e03c-fff2-291e-80a7-73f35d45c7e5/mzl.zejcvahm.png/53x53bb-85.png",
           "value": "hi how r u ",
           "color": "(UIColor.brown)"
           }]

}

您可以使用此代码从swift3中的文本json文件获取数据

     let filePath = Bundle.main.path(forResource: "nameoftheyourjsonTextfile", ofType: "json")


    let contentData = FileManager.default.contents(atPath: filePath!)
    let content = NSString(data: contentData!, encoding: String.Encoding.utf8.rawValue) as? String

    print(content)
    let json = try! JSONSerialization.jsonObject(with: contentData!) as! NSDictionary
    print(json)
    let app = json.object(forKey: "Scenes") as! NSArray!
    let _ : NSDictionary
    for dict in app! {
        let colorNam = (dict as AnyObject).object(forKey: "color") as! String
        print("colors are \(colorNam)")

       // let colour = UIColor(hexString: colorNam) {
       // colorsArray.append(colour.cgColor)
       // colorsArray.append(colorNam  as! UIColor)

        let value = (dict as AnyObject).object(forKey: "value") as! String
        print("the values are \(value)")
        valuesArray.append(value)

        let images = (dict as AnyObject).object(forKey: "image") as! String
        let url = URL(string: images as String)
        let data = try? Data(contentsOf: url!)
        print(data)
        let image1 = UIImage(data: data!)! as UIImage
        imagesArray.append(image1)
         print(image1)
            }

这适用于Linux上的Swift 3.1.1：

import Foundation

let s = try! String(contentsOfFile: "yo", encoding: .utf8)

写在ViewDidLoad

var error: NSError?
var paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)
var documentsDirectory = paths.first as String
var dataPath = documentsDirectory.stringByAppendingPathComponent("MyFolder")

if !NSFileManager.defaultManager().fileExistsAtPath(dataPath) {
    NSFileManager.defaultManager().createDirectoryAtPath(dataPath, withIntermediateDirectories: false, attributes: nil, error: &error)
} else {
    println("not creted or exist")
}

func listDocumentDirectoryfiles() -> [String] {
    if let documentDirectory = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).first as? String {
        let myFilePath = documentDirectory.stringByAppendingPathComponent("MyFolder")
        return NSFileManager.defaultManager().contentsOfDirectoryAtPath(myFilePath, error: nil) as [String]
    }
    return []
}

较早的解决方案可以回答问题，但是以我为例，在写入时删除文件的旧内容是一个问题。

因此，我创建了一段代码来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，但是我相信这是一个很好的起点。Swift 4.使用方法：

    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
    }
}

雨燕3.x-5.x

最好的示例是创建一个Logfile带有扩展名的本地文件，该扩展名.txt 可以在"Files App"以文件名和当前日期和时间

只需在info.plist中添加此代码即可启用这两个功能

  UIFileSharingEnabled
  LSSupportsOpeningDocumentsInPlace

和下面的这个功能

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

 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
}

Xcode 8.3.2 Swift 3.x。使用NSKeyedArchiver和NSKeyedUnarchiver

从文件中读取文件

let documentsDirectoryPathString = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first!
let documentsDirectoryPath = NSURL(string: documentsDirectoryPathString)!
let jsonFilePath = documentsDirectoryPath.appendingPathComponent("Filename.json")

let fileManager = FileManager.default
var isDirectory: ObjCBool = false

if fileManager.fileExists(atPath: (jsonFilePath?.absoluteString)!, isDirectory: &isDirectory) {

let finalDataDict = NSKeyedUnarchiver.unarchiveObject(withFile: (jsonFilePath?.absoluteString)!) as! [String: Any]
}
else{
     print("File does not exists")
}

将文件写入文件

NSKeyedArchiver.archiveRootObject(finalDataDict, toFile:(jsonFilePath?.absoluteString)!)