A Closer Look at Apollo`s File System API

The FileStream class provides methods that let your application read and write files.

Here’s the general process for reading and writing to a file:

1. Set up aFile object that points to the file you want to read or write.
   
   For details, see “Accessing Files and Directories,” earlier in this chapter. 
   
2. Instantiate aFileStream object—for example:
   
      var stream:FileStream = new FileStream();. 
   
3. Call theFileStream.open()orFileStream.openAsync()method, passing in theFileobject as thefileparameter and passing an appropriate file mode as thefileModeparameter. For example:
   
     stream.open(file, FileMode.READ);
   
   For more information, see “File Open Modes” later in this chapter.
   
4. If you called theFileStream.openAsync()method, set up the appropriate event listener functions.
   
   For more information, see “The open( ) and openAsync( ) Methods,” next.
   
5. Call the appropriate read and write method for your data.
   
   For more information, see “Read and Write Methods” later in this chapter
   
6. Close the file, using theFileStream.close()method. For example:
   
     stream.close();

Steps 3, 4, and 5 are described in more detail the sections that follow. First, here is a sample of code for reading UTF-8 text from a file synchronously:

  var file:File = File.appStorageDirectory;
  file = file.resolve("settings.xml");
  var stream:FileStream = new FileStream();
  stream.open(file, FileMode.READ);
  var data:String = stream.readUTFBytes(stream.
  bytesAvailable);
  stream.close();

Here is some code that reads the same data asynchronously:

  var file:File = File.appStorageDirectory;
  file = file.resolve("settings.xml");
  var stream:FileStream = new FileStream();
  stream.openAsync(file, FileMode.READ);
  stream.addEventListener(Event.COMPLETE, readData);
  var data:String;

  private function readData(event:Event):void {
    data = stream.readUTFBytes(stream.bytesAvailable);
    stream.close();
  }