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flutterdart
John
John

Reputation: 2791

How do you sort a list by bool in Dart

How do you sort a List in dart based on a bool value, the compareTo method doesn't work with bool. I want true values to appear at the top of the list.

Upvotes: 24

Views: 17180

Answers (3)

Степан Бушков
Степан Бушков

Reputation: 51

For List<bool>, you need to define a compare function:

final boollist = <bool>[false, true, true, false];

boollist.sort(
  (a, b) => (a == b ? 0 : (a ? 1 : -1)),
);

output: [false, false, true, true]

The reasons for this situation with bool in Dart can be read here.

Upvotes: 5

Matias Gold
Matias Gold

Reputation: 9

I just got the same issue, I solve it using the .toString() function. So it's sort separating the 0's to the 1's.

In this case I got a list of forms, some are synced and others no.

Here's my code:

final forms = state.forms
        ..sort(
          (a, b) => a.synced.toString().compareTo(b.synced.toString()),
        );

Hope it works for you.

Upvotes: -1

Christopher Moore
Christopher Moore

Reputation: 17141

You can define your own compare function for bool and pass it to the sort method of List.

Example with booleans as your bool List:

booleans.sort((a, b) {
  if(b) {
    return 1;
  }
  return -1;
});

This example tells the sort method that true elements should be sorted higher than false elements.

Upvotes: 49

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