在Swift中逐行读取文本文件？

Posted 2021-04-07

刚开始学习Swift，我已经从文本文件中读取了代码，应用程序显示了整个文本文件的内容。如何逐行显示并多次调用该行？

TextFile.txt包含以下内容。

1. 香蕉
2. 苹果
3. 梨
4. 草莓
5. 蓝莓
6. 黑醋栗

以下是目前的......

  if let path = NSBundle.mainBundle().pathForResource("TextFile", ofType: "txt"){
        var data = String(contentsOfFile:path, encoding: NSUTF8StringEncoding, error: nil)
            if let content = (data){
                TextView.text = content
    }

如果还有其他方式，请告诉我。非常感激

答案

Swift 3.0

if let path = Bundle.main.path(forResource: "TextFile", ofType: "txt") {
    do {
        let data = try String(contentsOfFile: path, encoding: .utf8)
        let myStrings = data.components(separatedBy: .newlines)
        TextView.text = myStrings.joined(separator: ", ")
    } catch {
        print(error)
    }
}

变量myStrings应该是数据的每一行。

使用的代码来自：用Obj-C编写的Reading file line by line in iOS SDK并使用NSString

检查以前版本的Swift的编辑历史记录。

另一答案

更新Swift 2.0 / Xcode 7.2

    do {
        if let path = NSBundle.mainBundle().pathForResource("TextFile", ofType: "txt"){
            let data = try String(contentsOfFile:path, encoding: NSUTF8StringEncoding)

            let myStrings = data.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet())
            print(myStrings)
        }
    } catch let err as NSError {
        //do sth with Error
        print(err)
    }

另外值得一提的是，此代码读取项目文件夹中的文件（因为使用了pathForResource），而不是例如设备的文件夹

另一答案

在Swift 5.0中执行此操作的最简单，最简单的方法可能如下：

import Foundation

// Determine the file name
let filename = "main.swift"

// Read the contents of the specified file
let contents = try! String(contentsOfFile: filename)

// Split the file into separate lines
let lines = contents.split(separator:"
")

// Iterate over each line and print the line
for line in lines {
    print("(line)")
}

归功于：https://wiki.codermerlin.com/mediawiki/index.php/Code_Snippet:_Print_a_File_Line-by-Line

另一答案

您可能确实希望立即读取整个文件。我打赌它很小。

但是，您希望将生成的字符串拆分为数组，然后在各种UI元素（如表格单元格）之间分发数组的内容。

一个简单的例子：

    var x: String = "abc
def"
    var y = x.componentsSeparatedByString("
")
    // y is now a [String]: ["abc", "def"]

另一答案

这不是很好，但我相信它有效（在Swift 5上）。这使用底层POSIX getline命令进行迭代和文件读取。

typealias LineState = (
  // pointer to a C string representing a line
  linePtr:UnsafeMutablePointer<CChar>?,
  linecap:Int,
  filePtr:UnsafeMutablePointer<FILE>?
)

/// Returns a sequence which iterates through all lines of the the file at the URL.
///
/// - Parameter url: file URL of a file to read
/// - Returns: a Sequence which lazily iterates through lines of the file
///
/// - warning: the caller of this function **must** iterate through all lines of the file, since aborting iteration midway will leak memory and a file pointer
/// - precondition: the file must be UTF8-encoded (which includes, ASCII-encoded)
func lines(ofFile url:URL) -> UnfoldSequence<String,LineState>
{
  let initialState:LineState = (linePtr:nil, linecap:0, filePtr:fopen(fileURL.path,"r"))
  return sequence(state: initialState, next: { (state) -> String? in
    if getline(&state.linePtr, &state.linecap, state.filePtr) > 0,
      let theLine = state.linePtr  {
      return String.init(cString:theLine)
    }
    else {
      if let actualLine = state.linePtr  { free(actualLine) }
      fclose(state.filePtr)
      return nil
    }
  })
}

以下是您可以使用它的方法：

for line in lines(ofFile:myFileURL) {
  print(line)
}