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."
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)
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)")
早期的解决方案回答了问题，但在我的情况下，删除文件的旧内容而写入是一个问题。
所以，我创建了一段代码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，但我相信这是一个很好的起点。斯威夫特4。
Usuage:
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
}
}
Xcode 8, Swift 3从应用程序包中读取文件的方法:
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()
你几乎总是想要一个行数组:
let r:[String] = "yourFile.txt"
.contentsOrBlank()
.characters
.split(separator: "\n", omittingEmptySubsequences:ignore)
.map(String.init)
