How do I concatenate string to an existing file?

Question

I've got a text file (it has content in it) and I want to append text to it. This is my code:

File outputFile=new File('hello.out');
      outputFile.createSync();
      List<String> readLines=files[i].readAsLinesSync(Encoding.UTF_8);
      for(int j=0;j<readLines.length;j++)
      {

        outputFile.writeAsStringSync(readLines[j], FileMode.APPEND); }

For some reason Dart put a yellow line under "FileMode.APPEND" and it says that it's an "extra argument". However, this link http://api.dartlang.org/docs/releases/latest/dart_io/File.html claims that it is optional.

Answer 1

The FileMode is an optional, named parameter, so you have to specify its name ('mode') when you call it. To solve your problem, change this:

outputFile.writeAsStringSync(readLines[j], FileMode.append);

to this:

outputFile.writeAsStringSync(readLines[j], mode: FileMode.append);