56 lines
2.3 KiB
ReStructuredText
56 lines
2.3 KiB
ReStructuredText
Thing Actions
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=============
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Introduction
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------------
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As well as properties, the OpenFlexure Microscope Server also supports Thing Actions.
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Thing Actions "invoke a function of the Thing, which manipulates state (e.g., toggling a lamp on or off) or triggers a process on the Thing (e.g., dim a lamp over time)." For the microscope, this would include moving the stage or taking a capture. Both of these require internal logic, and cannot be performed by changing a simple property.
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Actions should be *triggered* with POST requests *only*. Ideally, a view corresponding to an action should only support POST requests.
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Like properties, we use a special view class to identify a view as an action: ``ActionView``. For example, a view to perform a "quick-capture" action may look like:
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.. code-block:: python
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class QuickCaptureAPI(ActionView):
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"""
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Take an image capture and return it without saving
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"""
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# Expect a "use_video_port" boolean, which defaults to True if none is given
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args = {"use_video_port": fields.Boolean(missing=True)}
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# Our success response (200) returns an image (image/jpeg mimetype)
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responses = {
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200: {
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"content": { "image/jpeg": {} },
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}
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}
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def post(self, args):
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"""
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Take a non-persistant image capture.
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"""
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# Find our microscope component
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microscope = find_component("org.openflexure.microscope")
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# Open a BytesIO stream to be destroyed once request has returned
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with io.BytesIO() as stream:
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# Capture to our stream object
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microscope.camera.capture(stream, use_video_port=args.get("use_video_port"))
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# Rewind the stream
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stream.seek(0)
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# Return our image data using Flasks send_file function
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return send_file(io.BytesIO(stream.read()), mimetype="image/jpeg")
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In this example, we are also making use of the ``responses`` attribute, to document that our successful response (HTTP code 200) will return data with a mimetype ``image/jpeg``, as well as ``args`` to accept optional parameters with POST requests.
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Complete example
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----------------
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Adding this new view into our example extension, we now have:
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.. literalinclude:: ./example_extension/05_actions.py
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