Flutter and Dart - how can I format an integer date in one line of code

Question

How can I format an integer such as "20190331" to output as "2019-03-31" without firstly converting it to a date and without splitting it using substring. The date is stored as an integer in SQLite (SQFlite). I would like to do it in 1 line such as (pseudo code) Note: integer :

(pseudo) String sDate = fmt("####'-'##'-'##", map["DueDate"]);

I know that I could do it such as :

String sDate = map["DueDate"].toString();
sDate = sDate.substring(0,4)+'-'+sDate.substring(4,6)+'-'+sDate.substring(6,8);

That however is two lines of code, and Visual Studio Code turns it into 8 lines when formatted and I like to keep my code compact.

Possible duplicate of [How do I format a date with Dart?](https://stackoverflow.com/questions/16126579/how-do-i-format-a-date-with-dart) — Tirth Patel, Mar 31 '19 at 17:14
As I said, I want to format an integer not a date - in one line of code. — Brian Oh, Apr 01 '19 at 00:34

score 1 · Accepted Answer · answered Apr 01 '19 at 02:16

Write a function called fmt and call it as in your pseudo code.

String fmt(String f, int i) {
  StringBuffer sb = StringBuffer();
  RuneIterator format = RuneIterator(f);
  RuneIterator input = RuneIterator(i.toString());
  while (format.moveNext()) {
    var currentAsString = format.currentAsString;
    if (currentAsString == '#') {
      input.moveNext();
      sb.write(input.currentAsString);
    } else {
      sb.write(currentAsString);
    }
  }
  return sb.toString();
}

one line:

  print(fmt('####-##-##', 20190331));

Thanks Richard. I should have looked a few hours ago, because I wrote my own more generalized function. I'll try yours though, and if it works I'll give it a tick and I can probably learn from yours. — Brian Oh, Apr 01 '19 at 06:48

Flutter and Dart - how can I format an integer date in one line of code

1 Answers1