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."
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)")
Xcode 8.3.2 Swift 3.x。使用NSKeyedArchiver和NSKeyedUnarchiver
从文档中读取文件
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")
}
将文件写入文档
NSKeyedArchiver.archiveRootObject(finalDataDict, toFile:(jsonFilePath?.absoluteString)!)
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)")
}
}