data_source v0.1.4 Datasource
A Datasource is started as a process and implements a
function next which returns the next value of the
data source. E.g. for sensors the next function reads the
current value of the sensor and returns that. For file
sources, it may read the next line and so on.
If no data available or the datasource crashed the
next function will return :no_data
Link to this section Summary
Functions
Returns a specification to start this module under a supervisor
Get the next value of the data source.
If the Datasource crash or do not deliver data,
literally when it throws an exception, :no_data
will be returned
Instantiate a new Datasource with a initial_value and a given function fun
which will be called at next. The given function must return a tuple of kind
{ requested_value, new_data_source }. new_data_source will be the input
of the next call to Datasource.next/1
Link to this section Functions
Returns a specification to start this module under a supervisor.
See Supervisor.
Get the next value of the data source.
If the Datasource crash or do not deliver data,
literally when it throws an exception, :no_data
will be returned.
Examples:
A simple, endless counter
iex> {:ok, counter_source} = Datasource.start_link(1, fn(current) -> { current, current + 1 } end)
iex> (1..3) |> Enum.each( fn(_i) -> Datasource.next(counter_source) end)
iex> Datasource.next(counter_source)
4A Stream of data (which may have an end)
iex> {:ok, stream_source} = Datasource.start_link(Stream.map((0..2), &(&1)),
iex> fn(stream) -> { Stream.take(stream,1)
iex> |> Enum.map(&(&1))
iex> |> hd, Stream.drop(stream,1)}
iex> end
iex> )
iex> [
iex> Datasource.next(stream_source),
iex> Datasource.next(stream_source),
iex> Datasource.next(stream_source),
iex> Datasource.next(stream_source),
iex> Datasource.next(stream_source)
iex> ]
[0,1,2,:no_data,:no_data]Instantiate a new Datasource with a initial_value and a given function fun
which will be called at next. The given function must return a tuple of kind
{ requested_value, new_data_source }. new_data_source will be the input
of the next call to Datasource.next/1
Find examples at Datasource.next/0