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Use an S7 class as a type

Source: R/s7.R
s7_type.Rd

The class becomes an ordinary rdantic type: it can be a struct field, an argument of fn(), the element type of list_of(), and it parses a plain list – so from_json() builds real S7 objects, property by property, with every problem reported under its path.

Usage

s7_type(cls)

Arguments

cls

An S7 class, as returned by S7::new_class().

Value

A type.

Details

Property classes are translated where they carry over (class_integer, class_double, class_character, class_logical, class_list, class_Date, class_POSIXct, unconstrained class_data.frame values, unions, and nested S7 classes); anything else validates as anything. A property is required unless it declares a default. Expression-valued defaults remain S7's responsibility and are evaluated for each instance. Computed properties (a getter without a setter) are not input fields.

as_type() calls this for you, so an S7 class can be written directly wherever a type is expected.

See also

as_s7_class() for the other direction.

Examples

if (requireNamespace("S7", quietly = TRUE)) {
  library(S7)   # for `@`, which S7 supplies on R < 4.3

  Pin <- new_class("Pin", properties = list(
    lat = class_double,
    lon = class_double
  ))

  s7_type(Pin)
  schema(Pin)

  # an S7 class used as a struct field
  Trip <- struct("Trip", label = chr[1], start = Pin)
  t <- from_json(Trip, '{"label": "home", "start": {"lat": 1, "lon": 2}}')
  t$start

  try(from_list(Trip, list(label = "home", start = list(lat = "x", lon = 2))))
}
#> Error : 1 validation problem in Trip
#>   $start$lat  expected num, got chr[1] "x"  -- strings are never parsed implicitly