Expose fields in AffineTransform struct (or have a way to access the internal values)? about geo HOT 4 CLOSED

Of course you can access the coefficients, you can apply the transform to (0, 0), (1, 0) and (0, 1) and compute them 😄.

TBH they could even be public, but it's fine either way.

from geo.

I'm +1 on this. It doesn't look like there's any way to currently access those fields, even with a From impl. I don't think Rust has a concept of a getter so those attributes would have to become methods. I'm ok with using a-f letters for naming, since that seems pretty standard and we can additionally link to perrygeo's blog (I also go back to that blog post often!)

from geo.

I'm happy to have the fields be public, but I'm pretty sure the current field names are correct and meaningful in terms of affine transforms generally (see e.g. Shapely's affinity module); xoff and yoff are calculated offsets and I'd rather not rename them just to conform to Matt's terminology (it is a great blog post, btw).

from geo.

It doesn't look like there's any way to currently access those fields, even with a From impl. I don't think Rust has a concept of a getter so those attributes would have to become methods.

Found out at https://users.rust-lang.org/t/access-tuple-struct-with-one-element-more-ergonomically/27236 that there's an Index trait in std (see https://doc.rust-lang.org/std/ops/trait.Index.html) which seems to allow indexing into the array/matrix. Have started a draft PR at #1159 as a proof of concept. This enables indexing using transform["a"] or transform.index("a"). I could also rewrite things so that accessing the elements happens via transform.a() if that's more ergonomic. Edit: refactored implementation to use getter methods like transform.a().

Next point is to decide on the naming. To be clear, the current AffineTransform tuple struct doesn't set any names like c or xoff, it is only in the documentation. So we can go with either a,b,c,d,e,f naming or a,b,xoff,d,e,yoff.

from geo.