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)

Xcode 8。3. Swift;X或以上

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)
}

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)

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)
}

新的更简单和推荐的方法: 苹果建议使用url进行文件处理，这里的其他解决方案似乎已被弃用(见下面的评论)。 下面是新的简单的读写URL的方法:

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)

guard let fileURL = dir?.appendingPathComponent(fileName).appendingPathExtension("txt") else {
    fatalError("Not able to create URL")
}
    
// Writing to the file named Test
let outString = "Write this text to the file"
do {
    try outString.write(to: fileURL, atomically: true, encoding: .utf8)
} catch {
    assertionFailure("Failed writing to URL: \(fileURL), Error: " + error.localizedDescription)
}
    
// Reading it back from the file
var inString = ""
do {
    inString = try String(contentsOf: fileURL)
} catch {
    assertionFailure("Failed reading from URL: \(fileURL), Error: " + error.localizedDescription)
}
print("Read from the file: \(inString)")

这适用于Linux上的Swift 3.1.1:

import Foundation

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