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AggregateRoot pattern with apply_strategy methods.
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module MyAggregateRoot | |
MissingEventInApplyStrategy = Class.new(StandardError) | |
def load(stream_name, event_store:) | |
@version = -1 | |
event_store.read.stream(stream_name).forward.each do |event| | |
apply(event) | |
@version += 1 | |
end | |
@stream_name = stream_name | |
@unpublished_events = [] | |
end | |
def default_apply_strategy(event) | |
"apply_#{event.class.to_s.demodulize.underscore}" | |
end | |
def apply_strategy | |
{} | |
end | |
def apply(event) | |
mutate_state(event) | |
unpublished_events.push(event) | |
end | |
def mutate_state(event) | |
begin | |
callback_method = if apply_strategy.present? | |
apply_strategy.fetch(event.class.to_s.demodulize.underscore.to_sym) | |
else | |
default_apply_strategy(event) | |
end | |
rescue KeyError | |
raise MissingEventInApplyStrategy.new("#{event.class} is missing in apply_strategy.") | |
end | |
send(callback_method, event) | |
end | |
def store(event_store:) | |
unpublished_events.each do |event| | |
event_store.publish( | |
event, | |
stream_name: @stream_name, | |
expected_version: version | |
) | |
@version += 1 | |
end | |
@unpublished_events = [] | |
end | |
def unpublished_events | |
@unpublished_events ||= [] | |
end | |
def version | |
@version ||= -1 | |
end | |
end |
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