How do i delete text line from a txt file? ActionScript - actionscript-3

Question

Good morning! So here is basic code, which i get from the "Mobile Development with Adobe Flash Professional CS5.5 and Flash Builder 4.5" tutorial. Pretty much basic code, but those bastards didnt gave any information about DELETE function. THis is my first time application for this, so help is needed!
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
height="494" creationComplete="readFile()">
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
[Bindable] public var todo_items:ArrayCollection;
private function readFile():void
{
var todoFile:File =File.applicationStorageDirectory.resolvePath("todo.txt");
if (todoFile.exists)
{
var fs:FileStream = new FileStream();
fs.open(todoFile, FileMode.READ);
var result:String = fs.readUTFBytes(fs.bytesAvailable);
var items:Array = result.split("\n");
items.pop();
todo_items = new ArrayCollection(items);
fs.close();
}
else { trace("Aplication cant find the file");
}
}
private function writeFile():void
{
var todoFile:File = File.applicationStorageDirectory.resolvePath("todo.txt");
var fs:FileStream = new FileStream();
fs.open(todoFile, FileMode.APPEND);
fs.writeUTFBytes(task_txt.text + "\n");
fs.close();
readFile();
}
private function deleteFile():void
{
//????????????? HEEEEELP !!!!!!!!!!
}
]]>
</fx:Script>
<s:List id="todo_list" left="10" right="10" top="146" bottom="87" dataProvider="{todo_items}"/>
<s:Button left="11" right="10" top="69" height="65" label="Save task" click="writeFile()"
enabled="{task_txt.text.length > 0}"/>
<s:TextInput id="task_txt" left="10" right="10" top="10" height="51" prompt="Specify a task"/>
<s:Button left="10" right="10" bottom="14" label="Delete"
click="todo_items.removeItemAt(todo_list.selectedIndex); deleteFile()"
enabled="{todo_list.selectedIndex != -1}"/>

Answer 1

What you want to do is
read in all of the data from the file, just like readFile is doing.
delete from that data whatever lines you want to delete.
write the data back to the file - like writeFile is doing - in FileMode.WRITE mode, as you want it to overwrite, not append.
If you can't quite figure this out and need code instead of a guide, feel free to comment on here and I'll give you more than just pointers.
The code in readFile (all of it) reads in the data from the file into an ArrayCollection called todo_items.
If you want to remove an item from the file, you want to remove it from that ArrayCollection (something like todo_items.removeItemAt(index)).
Now, you have an ArrayCollection containing the data you want to be in the file. At this point, you need to imitate what writeFile() is doing, but with FileMode.WRITE, and you want to write out every item in your list, instead of the one item in the textbox you want to add.
private function deleteFile():void
{
var todoFile:File = File.applicationStorageDirectory.resolvePath("todo.txt");
var fs:FileStream = new FileStream();
fs.open(todoFile, FileMode.WRITE);
for(var item:String in todo_items)
{
fs.writeUTFBytes(item + "\n")
}
fs.close();
readFile();
}
On a somewhat related note - I don't think 'deleteFile' is a good name for what you are doing here. You might want a deleteItem() method that deletes the selected item, and then a saveFile() method that contains the code above.

Answer 2

I presume the deleteFile method is intended to delete the file? If so, Adobe's Reference documents the File class and deletion this is normally a good place to start when exploring classes.
private function deleteFile():void
{
var todoFile:File = File.applicationStorageDirectory.resolvePath("todo.txt");
todoFile.deleteFile()
}