An alias property for a subclass — scale_alias

Builds a getter/setter property that reads and writes an inherited property under a different name – how timescales::Calendar keeps @timeframes and geoscales::Geoscale keeps @geoframes working over the inherited @frames, so no existing code has to change when they become subclasses.

scale_alias_property(name)

Arguments

name: Name of the inherited property to alias.

Value

An S7 property.

Details

The setter is a no-op on NULL. S7's generated constructor writes every dynamic property once with NULL before the real values are set, so a setter that forwards NULL makes the class impossible to construct.

Examples

Aliased <- S7::new_class("Aliased",
  parent = scale_class(),
  properties = list(levels = scale_alias_property("frames"))
)
a <- Aliased(
  leaftable = scale_leaftable(scale_example()),
  frames = scale_frames(scale_example()),
  members = S7::prop(scale_example(), "members")
)
a@levels
#> [1] "sector" "class"  "group"  "unit"