behaviour 3.0.1
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This package adds support for behaviours. Behaviours are classes of which the instances are used as functions.
Behaviour #
Behaviours are classes of which the instances are used as functions.
Why? #
When writing code it is best to keep concerns separated and code testable. A behaviour helps with this. It is comparable with a global function which must be instantiated before it can be used. Because it is like a global function it only has one concern: executing one piece of logic, one behaviour. Because it still is a class, it can be injected where needed and/or mocked in testing.
A behaviour itself will never throw an exception. All exceptions/errors are
caught and returned in a ExceptionOr<TSuccess>
format which is either a
Failed
or a Success
. The Failed
contains the exception and the Success
contains the return value if any.
Getting started #
With input #
Behaviour<TIn, TOut>
The standard behaviour receives an input parameter of type TIn
and returns a
TOut
. If no output parameter is required it can be made void
. A behaviour
returns when called an Future<ExceptionOr<TSuccess>>
value. For more details
about that look at the Return value.
class CreateCustomer extends Behaviour<CreateCustomerParams, void> {
@override
Future<void> action(CreateCustomerParams input, BehaviourTrack? track) {
// TODO logic to create a customer
return Future.value();
}
}
class CreateCustomerParams {
const CreateCustomerParams({
required this.name,
required this.address,
required this.phoneNumber,
});
final String name;
final String address;
final String phoneNumber;
}
Without input #
BehaviourWithoutInput<TOut>
This behaviour does not receive an input parameter and returns a TOut
. If no
output parameter is required it can be made void
. A behaviour returns when
called an ExceptionOr<TSuccess>
value. For more details about that look at
the Return value.
class GetProfileData extends BehaviourWithoutInput<ProfileData> {
@override
Future<ProfileData> action(BehaviourTrack? track) {
return Future.value(ProfileData(
name: 'Wim',
birthday: DateTime(1993, 10, 07),
));
}
}
class ProfileData {
const ProfileData({
required this.name,
required this.birthday,
});
final String name;
final DateTime birthday;
}
Return value #
The return value of a behaviour is always an ExceptionOr<TSuccess>
value. This
is an abstract class with two implementers: Failed<TSuccess>
and Success<TSuccess>
with each an exception
and value
property
respectively. To determine what the received value is, the when
method is
provided (and thenWhen
for async methods).
Future<void> main() {
await getProfileData().thenWhen(
(exception) => log('Exception: $exception'),
(value) => log('value: $value'),
);
}
Behaviour monitor #
To monitor what the behaviour is doing a BehaviourMonitor
exits. This is a
factory class which creates a BehaviourTrack
. During the call of a behaviour,
the different methods of this track are called.
start
when the action is executedend
when the action has successfully been completed.stopWithException
when an exception happens.stopWithError
when anything else is caught.
This monitor can be used to do logging/analytics/...