TEXTFILE I/O : Don't write same things - unity3d

Question

I have a function that stores the coordinates and the name of that chunk, but the problem is that this function gets called everytime new chunks get generated, but the old ones keep being loaded if they are not far. So the result is that in the textfile, the function writes the chunks sometimes 2 times.
I don't want this to happen and have the function only write every chunk once.
The main problem is that I can't use StreamwWriter and StreamReader at the same time.
This is my code:
function saveLoadedChunk() {
var loadedChunks : GameObject[] = FindObjectsOfType(GameObject) as GameObject[];
var fileName = "C:/Reactor Games/chunks.txt";
var sw : System.IO.StreamWriter = new System.IO.StreamWriter(fileName, true);
for (var i = 0; i < loadedChunks.length ; i++) {
if(loadedChunks[i].name.Substring(0,5) == "Chunk" || loadedChunks[i].name.Substring(0,5) == "_TERR") {
if(loadedChunks[i].tag != "Player") {
var xco = loadedChunks[i].transform.position.x;
var yco = loadedChunks[i].transform.position.y;
var zco = loadedChunks[i].transform.position.z;
var stringToWrite = "Chunk (" + xco + ", " + yco + ", " + zco + ")";
sw.WriteLine(stringToWrite);
}
}
}
sw.Flush();
sw.Close();
}

Answer 1

Preamble
I mostly work with C#, so there could be some mistakes in syntax.
Solution
You can store all your chunks in memory set. Inside saveLoadedChunk you are going to update this set and then write it's contents to file:
var chunks: HashSet<Vector3> = new HashSet<Vector3>();
function saveLoadedChunk() {
var loadedChunks : GameObject[] = FindObjectsOfType(GameObject) as GameObject[];
for (var i = 0; i < loadedChunks.length ; i++)
if(loadedChunks[i].name.Substring(0,5) == "Chunk" || loadedChunks[i].name.Substring(0,5) == "_TERR")
if(loadedChunks[i].tag != "Player")
chunks.Add(loadedChunks[i].transform.position);
var fileName = "C:/Reactor Games/chunks.txt";
var sw : System.IO.StreamWriter = new System.IO.StreamWriter(fileName, false);
for (var chunk: Vector3 in chunks) {
var stringToWrite = "Chunk (" + chunk.x + ", " + chunk.y + ", " + chunk.z + ")";
sw.WriteLine(stringToWrite);
}
}
The drawback here is:
That you start with blank chunks set every time app is launched.
You store all the chunks' coords in memory. But I wouldn't say that this is drawback until you have really-really lot of chunks.
In order to solve first problem you need to fill chunks with corrds stored in C:/Reactor Games/chunks.txt once the app is started.