Support Nullable Types on props | Flutter 2.0 and Dart 2.12 upgrade

[Edorin9]

Describe the bug
The props override property of an equatable doesn't support nullable (eg: String?) values.

To Reproduce
Steps to reproduce the behavior:

1. Upgrade flutter on stable channel (flutter channel stable && flutter upgrade)
2. Upgrade dart sdk version to sdk: ">=2.12.0 <3.0.0"
3. Create an equatable with a nullable property (final String? name)
4. Pass the 'name' property in the equatable props array

@override
  List<Object> get props => [name];

Expected behavior
No IDE errors/build errors should show up

A possible workaround on my side is to
Assign a fallback value / ternary, which I would say is not reecommended

@override
  List<Object> get props => [name ?? ''];

Additional context
The element type 'String?' can't be assigned to the list type 'Object'.

[felangel]

Hi @Edorin9 👋
Thanks for opening an issue!

If you want to use nullable props you can just update the props override:

@override
List<Object?> get props => [name];

Hope that helps 👍

[felangel]

@Edorin9 can this be closed or are you still having trouble with nullable props?

[Edorin9]

Thanks for the reply @felangel. We can close it for now. I've actually downgraded flutter and quit upgrading a project, since there are other packages that needs updating as well.

[JakeHadley]

@felangel I was having the same issue, with vscode, I added in the nullable operator (?) and I got this error from vscode...

('List<Object>? Function()') isn't a valid override of 'Equatable.props' ('List<Object?> Function()').dart(invalid_override)

Granted, my class currently doesn't have any props, so I just have List<Object>? get props => null; which causes this error. Do I need to override the get props if I don't have any props?

[felangel]

@JakeHadley if you don’t have any props the override should be:

List<Object> get props => [];

If you have nullable props it should be:

List<Object?> get props => [propA, propB];

Hope that helps 👍

[JakeHadley]

Ah yes, that helps a lot. Thanks!

…

On Wed, Apr 28, 2021, 00:31 Felix Angelov ***@***.***> wrote: @JakeHadley <https://github.com/JakeHadley> the override should be: List<Object?> get props => []; Hope that helps 👍 — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#111 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIPP6MNLEZTHBSAF45ORLQDTK6TTZANCNFSM4YSS4KDA> .

[luandnguyen]

@felangel Appreciate the solution. Should this be mentioned in the README?

[ariefwijaya]

@JakeHadley if you don’t have any props the override should be:

List<Object> get props => [];

If you have nullable props it should be:

List<Object?> get props => [propA, propB];

Hope that helps 👍

I can't make this work. I've tried List<Object?> but I got this 'NotificationNavigateScreen.props' ('List<Object?> Function()') isn't a valid override of 'NotificationState.props' ('List<Object> Function()')

[robyhuzwandar]

@JakeHadley if you don’t have any props the override should be:
List<Object> get props => [];
If you have nullable props it should be:
List<Object?> get props => [propA, propB];
Hope that helps 👍

I can't make this work. I've tried List<Object?> but I got this 'NotificationNavigateScreen.props' ('List<Object?> Function()') isn't a valid override of 'NotificationState.props' ('List<Object> Function()')

Hi @felangel how about that I got the error too

[felangel]

@JakeHadley if you don’t have any props the override should be:
List<Object> get props => [];
If you have nullable props it should be:
List<Object?> get props => [propA, propB];
Hope that helps 👍

I can't make this work. I've tried List<Object?> but I got this 'NotificationNavigateScreen.props' ('List<Object?> Function()') isn't a valid override of 'NotificationState.props' ('List<Object> Function()')

Hi @felangel how about that I got the error too

Can you share a minimal reproduction sample?

[ariefwijaya]

Sorry, my bad. I found it. I need to use List<Object?> in my abstract class when extending Equatable. Just because my abstract is not nullable, it will force the child to be non-nullable too.

[Ashrafe]

Sorry, my bad. I found it. I need to use List<Object?> in my abstract class when extending Equatable. Just because my abstract is not nullable, it will force the child to be non-nullable too.

yea that's it ty

[AnnaPS]

@JakeHadley if you don’t have any props the override should be:

List<Object> get props => [];

If you have nullable props it should be:

List<Object?> get props => [propA, propB];

Hope that helps 👍

Thank you Felix, I was looking for this solution :)