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."
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
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)
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)")
