CastOr provide a .castOr<T>(()), .castOrNull<T>() helpers and extension to safely transform/cast and provide defaults values
when you deal with untyped data. The package provide also a .let<T>() implementation (similar to kotlin).
This package try to solve 2 typical issue when dealing with nullsafety on your dart projects.
as casting will fail if we not ensure the type before, and the usage of the ! postfix null promotion operator.
Both usage should be avoided at all cost.
Consider the following code :
void main() {
dynamic a = 3;
final String? s;
try {
s = a as S;
} catch (e) {
s = null;
}
}which can be solved
import 'package:castor/castor.dart';
void main() {
dynamic dyn = null;
final obj = (dyn as Object?);
// the basic [castOr] always expect to get an uwrapped value of the input type
int b = obj.castOr<String>(a, (_) => 'alternative string').length;
int c = castOr<int>(a, (_) => 'alternative string').length;
// the [castOrNull] equivalent just accept a nullable when casting is wrong
bool? asHelper = castOrNull<bool>(a, (_) => 'alternative string').length;
bool? asExt = obj?.castOrNull();
int? s = castOrNull<String>(a)?.length;
/// and with [a] an Object?
int s2 = a?.castOr<String>((val) => 'alternative string').length;
int? s = a?.castOrNull<String>(a)?.length;
}It's ok for now but this will crash probably at some time if someone remove the if clause, because no static analysis will check on the code.
You want ensure that the given value is of the correct type without having
to mix with error prone as keyword. Consider the following code :
void main() {
dynamic a = 3;
final String? s;
try {
s = a as S;
} catch (e) {
s = null;
}
}import 'package:castor/castor.dart';
void main () {
/// considering [a] a dynamic
int s2 = castOr<String>(a, (_) => 'alternative string').length;
int? s = castOrNull<String>(a)?.length;
/// and with [a] an Object?
int s2 = a?.castOr<String>((val) => 'alternative string').length;
int? s = a?.castOrNull<String>(a)?.length;
}promoting with the ! should be avoided at all cost. With the following code :
if (this.a != null) this.a!.length;It's ok for now but this will crash probably at some time if someone remove the if clause, because no static analysis will check on the code.
Before writing this package, I found many other alternative solutions, most of them trying to mimic the .let
behavior of kotlin, and other guard keyword to ensure null safety everywhere in the code.
I choose to publish this little one because of the cute name but mostly about the small footprint or your codebase.
Regarding dart and null safety right now, there is 3 common pitfalls when you start believing in nullsafety in dart.
- First is the
dynamickeyword, and the!postfix null promotion operator. Both should be avoid at all cost and you should prefer theObject?which is not equivalent but can be simply switch - Secondly, you'll have to check the
askeyword, which without concealing it into a try/catch block or prefixing withif (a is b)control block. - And finally, there is a lot of throwing methods out there that you can't avoid staticaly without tools like DCM.
"Castor" is the french word for "Beaver". That's why you should find a beaver symbol 🦫 there and there.
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credits : https://textart.sh/topic/beaver- Discussion about the
letkeyword dart-lang/language#2703 - Null safety patterns https://github.com/dart-lang/language/blob/main/accepted/3.0/patterns/feature-specification.md