Writing a list of strings to a file - dart

Question

From the API page, I gather there's no function for what I'm trying to do. I want to read text from a file storing it as a list of strings, manipulate the text, and save the file. The first part is easy using the function:
abstract List<String> readAsLinesSync([Encoding encoding = Encoding.UTF_8])
However, there is no function that let's me write the contents of the list directly to the file e.g.
abstract void writeAsLinesSync(List<String> contents, [Encoding encoding = Encoding.UTF_8, FileMode mode = FileMode.WRITE])
Instead, I've been using:
abstract void writeAsStringSync(String contents, [Encoding encoding = Encoding.UTF_8, FileMode mode = FileMode.WRITE])
by reducing the list to a single string. I'm sure I could also use a for loop and feed to a stream line by line. I was wondering two things:
Is there a way to just hand the file a list of strings for writing?
Why is there a readAsLinesSync but no writeAsLinesSync? Is this an oversight or a design decision?
Thanks

Answer 1

I just made my own export class that handles writes to a file or for sending the data to a websocket.
Usage:
exportToWeb(mapOrList, 'local', 8080);
exportToFile(mapOrList, 'local/data/data.txt');
Class:
//Save data to a file.
void exportToFile(var data, String filename) =>
new _Export(data).toFile(filename);
//Send data to a websocket.
void exportToWeb(var data, String host, int port) =>
new _Export(data).toWeb(host, port);
class _Export {
HashMap mapData;
List listData;
bool isMap = false;
bool isComplex = false;
_Export(var data) {
// Check is input is List of Map data structure.
if (data.runtimeType == HashMap) {
isMap = true;
mapData = data;
} else if (data.runtimeType == List) {
listData = data;
if (data.every((element) => element is Complex)) {
isComplex = true;
}
} else {
throw new ArgumentError("input data is not valid.");
}
}
// Save to a file using an IOSink. Handles Map, List and List<Complex>.
void toFile(String filename) {
List<String> tokens = filename.split(new RegExp(r'\.(?=[^.]+$)'));
if (tokens.length == 1) tokens.add('txt');
if (isMap) {
mapData.forEach((k, v) {
File fileHandle = new File('${tokens[0]}_k$k.${tokens[1]}');
IOSink dataFile = fileHandle.openWrite();
for (var i = 0; i < mapData[k].length; i++) {
dataFile.write('${mapData[k][i].real}\t'
'${mapData[k][i].imag}\n');
}
dataFile.close();
});
} else {
File fileHandle = new File('${tokens[0]}_data.${tokens[1]}');
IOSink dataFile = fileHandle.openWrite();
if (isComplex) {
for (var i = 0; i < listData.length; i++) {
listData[i] = listData[i].cround2;
dataFile.write("${listData[i].real}\t${listData[i].imag}\n");
}
} else {
for (var i = 0; i < listData.length; i++) {
dataFile.write('${listData[i]}\n');
}
}
dataFile.close();
}
}
// Set up a websocket to send data to a client.
void toWeb(String host, int port) {
//connect with ws://localhost:8080/ws
//for echo - http://www.websocket.org/echo.html
if (host == 'local') host = '127.0.0.1';
HttpServer.bind(host, port).then((server) {
server.transform(new WebSocketTransformer()).listen((WebSocket webSocket) {
webSocket.listen((message) {
var msg = json.parse(message);
print("Received the following message: \n"
"${msg["request"]}\n${msg["date"]}");
if (isMap) {
webSocket.send(json.stringify(mapData));
} else {
if (isComplex) {
List real = new List(listData.length);
List imag = new List(listData.length);
for (var i = 0; i < listData.length; i++) {
listData[i] = listData[i].cround2;
real[i] = listData[i].real;
imag[i] = listData[i].imag;
}
webSocket.send(json.stringify({"real": real, "imag": imag}));
} else {
webSocket.send(json.stringify({"real": listData, "imag": null}));
}
}
},
onDone: () {
print('Connection closed by client: Status - ${webSocket.closeCode}'
' : Reason - ${webSocket.closeReason}');
server.close();
});
});
});
}
}

Answer 2

I asked Mads Agers about this. He works on the io module. He said that he decided not to add writeAsLines because he didn't find it useful. For one it is trivial to write the for loop and the other thing is that you have to parameterize it which the kind of line separator that you want to use. He said he can add it if there is a strong feeling that it would be valuable. He didn't immediately see a lot of value in it.