建议异步读写文件!用纯Swift很容易做到， 以下是协议:

protocol FileRepository {
    func read(from path: String) throws -> String
    func readAsync(from path: String, completion: @escaping (Result<String, Error>) -> Void)
    func write(_ string: String, to path: String) throws
    func writeAsync(_ string: String, to path: String, completion: @escaping (Result<Void, Error>) -> Void)
}

正如您所看到的，它允许您同步或异步地读取和写入文件。

以下是我在Swift 5中的实现:

class DefaultFileRepository {
    
    // MARK: Properties
    
    let queue: DispatchQueue = .global()
    let fileManager: FileManager = .default
    lazy var baseURL: URL = {
        try! fileManager
            .url(for: .libraryDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
            .appendingPathComponent("MyFiles")
    }()
    
    
    // MARK: Private functions
    
    private func doRead(from path: String) throws -> String {
        let url = baseURL.appendingPathComponent(path)
        
        var isDir: ObjCBool = false
        guard fileManager.fileExists(atPath: url.path, isDirectory: &isDir) && !isDir.boolValue else {
            throw ReadWriteError.doesNotExist
        }
        
        let string: String
        do {
            string = try String(contentsOf: url)
        } catch {
            throw ReadWriteError.readFailed(error)
        }
        
        return string
    }
    
    private func doWrite(_ string: String, to path: String) throws {
        let url = baseURL.appendingPathComponent(path)
        let folderURL = url.deletingLastPathComponent()
        
        var isFolderDir: ObjCBool = false
        if fileManager.fileExists(atPath: folderURL.path, isDirectory: &isFolderDir) {
            if !isFolderDir.boolValue {
                throw ReadWriteError.canNotCreateFolder
            }
        } else {
            do {
                try fileManager.createDirectory(at: folderURL, withIntermediateDirectories: true)
            } catch {
                throw ReadWriteError.canNotCreateFolder
            }
        }
        
        var isDir: ObjCBool = false
        guard !fileManager.fileExists(atPath: url.path, isDirectory: &isDir) || !isDir.boolValue else {
            throw ReadWriteError.canNotCreateFile
        }
        
        guard let data = string.data(using: .utf8) else {
            throw ReadWriteError.encodingFailed
        }
        
        do {
            try data.write(to: url)
        } catch {
            throw ReadWriteError.writeFailed(error)
        }
    }
    
}


extension DefaultFileRepository: FileRepository {
    func read(from path: String) throws -> String {
        try queue.sync { try self.doRead(from: path) }
    }
    
    func readAsync(from path: String, completion: @escaping (Result<String, Error>) -> Void) {
        queue.async {
            do {
                let result = try self.doRead(from: path)
                completion(.success(result))
            } catch {
                completion(.failure(error))
            }
        }
    }
    
    func write(_ string: String, to path: String) throws {
        try queue.sync { try self.doWrite(string, to: path) }
    }
    
    func writeAsync(_ string: String, to path: String, completion: @escaping (Result<Void, Error>) -> Void) {
        queue.async {
            do {
                try self.doWrite(string, to: path)
                completion(.success(Void()))
            } catch {
                completion(.failure(error))
            }
        }
    }
    
}


enum ReadWriteError: LocalizedError {
    
    // MARK: Cases
    
    case doesNotExist
    case readFailed(Error)
    case canNotCreateFolder
    case canNotCreateFile
    case encodingFailed
    case writeFailed(Error)
}

建议异步读写文件!用纯Swift很容易做到， 以下是协议:

protocol FileRepository {
    func read(from path: String) throws -> String
    func readAsync(from path: String, completion: @escaping (Result<String, Error>) -> Void)
    func write(_ string: String, to path: String) throws
    func writeAsync(_ string: String, to path: String, completion: @escaping (Result<Void, Error>) -> Void)
}

正如您所看到的，它允许您同步或异步地读取和写入文件。

以下是我在Swift 5中的实现:

class DefaultFileRepository {
    
    // MARK: Properties
    
    let queue: DispatchQueue = .global()
    let fileManager: FileManager = .default
    lazy var baseURL: URL = {
        try! fileManager
            .url(for: .libraryDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
            .appendingPathComponent("MyFiles")
    }()
    
    
    // MARK: Private functions
    
    private func doRead(from path: String) throws -> String {
        let url = baseURL.appendingPathComponent(path)
        
        var isDir: ObjCBool = false
        guard fileManager.fileExists(atPath: url.path, isDirectory: &isDir) && !isDir.boolValue else {
            throw ReadWriteError.doesNotExist
        }
        
        let string: String
        do {
            string = try String(contentsOf: url)
        } catch {
            throw ReadWriteError.readFailed(error)
        }
        
        return string
    }
    
    private func doWrite(_ string: String, to path: String) throws {
        let url = baseURL.appendingPathComponent(path)
        let folderURL = url.deletingLastPathComponent()
        
        var isFolderDir: ObjCBool = false
        if fileManager.fileExists(atPath: folderURL.path, isDirectory: &isFolderDir) {
            if !isFolderDir.boolValue {
                throw ReadWriteError.canNotCreateFolder
            }
        } else {
            do {
                try fileManager.createDirectory(at: folderURL, withIntermediateDirectories: true)
            } catch {
                throw ReadWriteError.canNotCreateFolder
            }
        }
        
        var isDir: ObjCBool = false
        guard !fileManager.fileExists(atPath: url.path, isDirectory: &isDir) || !isDir.boolValue else {
            throw ReadWriteError.canNotCreateFile
        }
        
        guard let data = string.data(using: .utf8) else {
            throw ReadWriteError.encodingFailed
        }
        
        do {
            try data.write(to: url)
        } catch {
            throw ReadWriteError.writeFailed(error)
        }
    }
    
}


extension DefaultFileRepository: FileRepository {
    func read(from path: String) throws -> String {
        try queue.sync { try self.doRead(from: path) }
    }
    
    func readAsync(from path: String, completion: @escaping (Result<String, Error>) -> Void) {
        queue.async {
            do {
                let result = try self.doRead(from: path)
                completion(.success(result))
            } catch {
                completion(.failure(error))
            }
        }
    }
    
    func write(_ string: String, to path: String) throws {
        try queue.sync { try self.doWrite(string, to: path) }
    }
    
    func writeAsync(_ string: String, to path: String, completion: @escaping (Result<Void, Error>) -> Void) {
        queue.async {
            do {
                try self.doWrite(string, to: path)
                completion(.success(Void()))
            } catch {
                completion(.failure(error))
            }
        }
    }
    
}


enum ReadWriteError: LocalizedError {
    
    // MARK: Cases
    
    case doesNotExist
    case readFailed(Error)
    case canNotCreateFolder
    case canNotCreateFile
    case encodingFailed
    case writeFailed(Error)
}

我只想给你们看第一部分，也就是阅读部分。以下是简单的阅读方法:

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")!)

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)
}

假设你已经将你的文本文件data.txt移动到你的Xcode-project中(使用拖放并勾选“必要时复制文件”)，你可以像在Objective-C中一样执行以下操作:

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: 对于从Bundle (iOS)读取文件，您可以使用:

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)!

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)

为了避免混淆并增加易用性，我创建了两个函数，用于向documents目录中的文件读取和写入字符串。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
}

下面是一个使用它们的例子:

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.'

希望这能有所帮助!

Xcode版本:6.3.2