I want to create a new subclass of the mesh3d S3 object class, and a corresponding method for rgl::shade3d. The new method will be closely modelled on the existing shade3d function but with different defaults. This is what I tried initially:
library(rgl)
# Create a test object
obj <- translate3d(tetrahedron3d(col = "red"), 0, 0, 0)
# Create a new S3 subclass
obj <- structure(obj, class = c("myclass", "mesh3d", "shape3d"))
# Creating a shade3d method for myclass
shade3d.myclass <- function(mesh, ...) {
shade3d(mesh, ..., lit = F)
}
shade3d(obj)
# Error: C stack usage 15923488 is too close to the limit
As far as I can figure out, this is because the function tries to call itself. To prevent this, I need to specify the method I’m referring to within my function.
methods(shade3d)
# [1] shade3d.mesh3d* shade3d.myclass shade3d.shapelist3d*
shade3d.myclass <- function(mesh, ...) {
rgl:::shade3d.mesh3d(mesh, ..., lit = F)
}
shade3d(obj)
This now works. But I’ve read that using ::: to make use of hidden functions from another package is not good practice. Presumably it has been set as hidden for a reason. Do I have any other options here? Is this an acceptable use case for :::?
1
If you are just changing defaults, try NextMethod instead.
# Creating a shade3d method for myclass
shade3d.myclass <- function(mesh, ...) {
NextMethod(mesh, ..., lit = FALSE)
}
Or even better, be user-friendly and set the defaults in the function definition.
# Creating a shade3d method for myclass
shade3d.myclass <- function(mesh, ..., lit = FALSE) {
NextMethod(mesh, ..., lit = lit)
}