[PG-172]: add 'simpler' aggregate trait #75
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potential future improvements: - the Aggregate should not need an `event_store` method on it; could break this out into another trait - `handle_command` could return `Vec<Events>` to be saved transactionally
emturner
changed the title
| @@ -58,8 +55,8 @@ impl Aggregate for CreditCardAggregate { | |||
| } | |||
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| // No state for credit_card aggregate | |||
| fn apply_event(_id: &Uuid, state: CreditCardState, event: &StoreEvent<Self::Event>) -> CreditCardState { | |||
| match event.payload() { | |||
| fn apply_event(state: CreditCardState, event: &Self::Event) -> CreditCardState { | |||
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I left the event wrapped inside the StoreEvent because I thought that maybe one of the inner field could have been useful for the state. Eg. assumptions over sequence_number or occurred_on. WDYT?
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I think that it makes sense for projectors etc to take the StoreEvent - since any metadata currently lives there. (separately - I guess it could be worth thinking about how we handle metadata/tracing properly? (e.g. how pass through correlation_id through the system)
but it feels a bit odd to me for the core aggregate to have access to things like occured_on/sequence_number - depending on sequence_number in the state feels a bit flaky. And as with occured_on, if the aggregate needs a sequence or a timestamp then potentially they should be placed in the commands/events explicitly?
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https://prima-assicurazioni-spa.myjetbrains.com/youtrack/issue/PG-172
closes #68
Renames
AggregatetoAggregateManagerand introduces a new, simplifiedAggregatetrait. The aim is to reduce the implementation complexity of aggregates for the majority of use-cases (ie pure aggregates).There is a default implementation of
AggregateManagerforAggregate- so that implementors of theAggregatetrait get the correct 'pipelining' behaviour for free.demo tracking branch of platform-global
#69 is in progress - but was getting rather large so wanted to split this out first