从文本文件中读取和写入字符串

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从文本文件中读取和写入字符串

我需要读写文本文件的数据，但我一直没有弄清楚如何操作。

我在Swift的iBook中找到了这个示例代码，但我还是不知道如何读写数据。

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."

admin 更改状态以发布 2023年5月22日
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2 答案

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假设你已经把文本文件data.txt移动到Xcode项目中(使用拖放并选中"必要时复制文件"),你可以像在Objective-C中一样做以下操作:

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:
要从Bundle(iOS)读取文件,你可以使用:

let path = NSBundle.mainBundle().pathForResource("FileName", ofType: "txt")
var text = String(contentsOfFile: path!, encoding: NSUTF8StringEncoding, error: nil)!
println(text)

更新Swift 3:

let path = Bundle.main.path(forResource: "data", ofType: "txt") // file path for file "data.txt"
var text = String(contentsOfFile: path!, encoding: NSUTF8StringEncoding, error: nil)!

对于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)

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为了读写，应该使用可写的位置，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 playground 上测试它。

Swift 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 */}
}

Swift 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 */}
}

Swift 1.x

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)
}

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