Spear v1.4.0

View Source Spear.ExpectationViolation (Spear v1.4.0)

A structure representing how an append request's expectations were violated

expectations

 Expectations

A client may exert expectations on write requests which will fail the request if violated. Any of these values may be passed to the :expect option of Spear.append/4:

  • :any - (default) any stream. Cannot be violated.
  • :exists - the EventStoreDB stream must exist prior to the proposed events being written
  • :empty - the EventStoreDB stream must not exist prior to the proposed events being written
  • revision - any positive integer representing the current size of the stream. The head of the EventStoreDB stream must match this revision number in order for the append request to succeed.

If an expectation is violated, the return signature will be {:error, %Spear.ExpectationViolation{}}, which gives information about the expectation and the current revision. See t/0.

Expectations may also be set in Spear.delete_stream/3, although if expectations set on a deletion request are violated, EventStoreDB returns a gRPC error response instead of this struct.

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Types

t()

A structure representing how an append request's expectations were violated

Link to this section Types

Link to this type

t()

View Source (since 0.1.0) 
@type t() :: %Spear.ExpectationViolation{
  current: pos_integer() | :empty,
  expected: pos_integer() | :empty | :exists | :any
}

A structure representing how an append request's expectations were violated

This struct is returned on calls to Spear.append/4 which set an expectation on the current stream revision with the :expect option.

:current is not the number of events in the EventStoreDB stream but rather the current event revision. If three events are appended to an empty stream, the :current will be 2. Note that deletions do not reset a stream's revision number.

examples

 Examples 

# say EventStoreDB stream "stream_that_should_be_empty" has 6 events
iex> Spear.append(events, conn, "stream_that_should_be_empty", expect: :empty)
{:error, %Spear.ExpectationViolation{current: 5, expected: :empty}}

# say EventStoreDB stream "stream_that_should_have_events" has no events
iex> Spear.append(events, conn, "stream_that_should_have_events", expect: :exists)
{:error, %Spear.ExpectationViolation{current: :empty, expected: :exists}}