Dart file read to var - file-io

Question

I have looked all over can not find how to read input from file into variables.
trying to do this
in c++
ifstream myFile;
myFile.open("filename.txt");
while(!file.eof()){
myFile >> var1 >> var2 >> etc...
following dart documentation ive got the file open and all but i cannot find examples likes this. would appreciate help and also links to relevant Dart examples , nothing web/app related. just trying to read from a file and do some computation with the stuff thats in the file.
(file has grades and im computing avgs).
sample input.txt file (d123 some student unique id, the numbers are grades).
d123 90 89 60 77 65 100
d124 70 79 88 75 57 89
thanks

Answer 1

You can find the below sample snippet. As I am not sure how big is the file, I am using async and stream API to process line by line. However, if your input is not so big, you can just read entire file at once, and perform the same step. Here are some links with good documentation dart:io, dart:convert
import 'dart:io';
import 'dart:convert';
import 'dart:async';
main(List<String> arguments) {
final file = new File('input/input.txt');
Stream<List<int>> inputStream = file.openRead();
inputStream.transform(UTF8.decoder).transform(new LineSplitter()).listen(
(String line) {
// calculate average score
List<String> list = line.split(" ");
var studentId = list[0];
var averageScore = list
.sublist(1)
.map((value) => int.parse(value))
.reduce((a, b) => a + b) / (list.length - 1);
print('${studentId} has average score of ${averageScore}');
}, onDone: () {
print('File is succeessfully read.');
}, onError: (e) {
print(e.toString());
});
}

Answer 2

I would just read the entire file, split into lines, and then assign variables from there:
import "dart:io";
main() {
var file = new File('input/input.txt');
var lines = file.readAsLinesSync();
var var1 = lines[0];
var var2 = lines[1];
...
}
If it's really important to read only part of the file, then you can use the solution above.