ios 在 Swift 中逐行读取文本文件？

Read a text file line by line in Swift?

提问by ScarletEnvy

Just started learning Swift, I have got my code to read from the text file, and the App displays the content of the Entire Text file. How can I display line by line and call upon that line multiple times?

刚开始学习 Swift，我已经从文本文件中读取了我的代码，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 contains the following.

TextFile.txt 包含以下内容。

1. Banana
2. Apple
3. pear
4. strawberry
5. blueberry
6. blackcurrent

1. 香蕉
2. 苹果
3. 梨
4. 草莓
5. 蓝莓
6. 黑流

the following is what currently have..

以下是目前有..

  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
    }

also if there is another way, of doing this please let me know. Much appreciated

另外，如果有另一种方式，请让我知道。非常感激

回答by Caleb

Swift 3.0

斯威夫特 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)
    }
}

The variable myStringsshould be each line of the data.

变量myStrings应该是数据的每一行。

The code used is from: Reading file line by line in iOS SDKwritten in Obj-C and using NSString

使用的代码来自： Reading file line by line in iOS SDKwrite in Obj-C and using NSString

Check edit history for previous versions of Swift.

检查以前版本的 Swift 的编辑历史记录。

回答by glace

Update for Swift 2.0 / Xcode 7.2

Swift 2.0 / Xcode 7.2 更新

    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)
    }

Also worth to mention is that this code reads a file which is in the project folder (since pathForResource is used), and not in e.g. the documents folder of the device

另外值得一提的是，这段代码读取了一个位于项目文件夹中的文件（因为使用了 pathForResource），而不是在设备的文档文件夹中

回答by algal

This is not pretty, but I believe it works (on Swift 5). This uses the underlying POSIX getlinecommand for iteration and file reading.

这并不漂亮，但我相信它有效（在 Swift 5 上）。这使用底层 POSIXgetline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
    }
  })
}

Here is how you might use it:

以下是您可以如何使用它：

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

回答by NerdOfCode

Probably the simplest, and easiest way to do this in Swift 5.0, would be the following:

在 Swift 5.0 中执行此操作的最简单、最简单的方法可能是以下内容：

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:"\n")

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

Note: This reads the entire file into memory, and then just iterates over the file in memory to produce lines....

注意：这将整个文件读入内存，然后只是迭代内存中的文件以生成行....

Credit goes to: https://wiki.codermerlin.com/mediawiki/index.php/Code_Snippet:_Print_a_File_Line-by-Line

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

回答by BaseZen

You probably do want to read the entire file in at once. I bet it's very small.

您可能希望一次读取整个文件。我敢打赌它很小。

But then you want to split the resulting string into an array, and then distribute the array's contents among various UI elements, such as table cells.

但是随后您想将结果字符串拆分为一个数组，然后将数组的内容分布在各种 UI 元素（例如表格单元格）中。

A simple example:

一个简单的例子：

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