Implement Getters for :PV

[andrew-saydjari]

I am reading a WCS transform from a header and running into "getter for :pv not implemented". I would be willing to put some effort in this direction. Has there been any progress/thoughts on this? Where are the get_field() functions defined?

[mileslucas]

I don't know much about WCS or what pv is, but the definition is inside the getproperty method-

WCS.jl/src/WCS.jl

Lines 503 to 505 in ae3502a

	# PVCard[]
	elseif k === :pv
	error("pv getter not yet implemented")

The git blame is Kyle Barbary, so there's probably no information about status or ideas. Perhaps astropy has some clues that can lead us to an implementation?

[andrew-saydjari]

Sure. But I guess what I was asking is for an example of a getfield definition. I had found 503-505, but when looking at

    if k == :naxis
        v = getfield(wcs, k)

a property which is implemented, I could not find where the function getfield was defined.

And ok, translating astropy and benchmarking was my first plan.

[mileslucas]

Oh, sorry for the misunderstanding!

getfield is a Julia base function for accessing the fields of a struct. So the "implementation" in that sense is just returning the stored value. This isn't something we overwrite in our code.

I looked in the WCS struct and there actually is a pv value, but it's stored in a card structure. I bet that's why it wasn't fully implemented.