Define an S7 class with rdantic field types

struct() with an S7 class as the result: the fields are declared exactly as they would be for a struct, and what comes back is a real S7 class whose properties validate – and coerce – through those types on construction and on @<-, raising the usual typed_error.

Usage

s7_struct(
  .name,
  ...,
  .description = NULL,
  .parent = NULL,
  .extra = c("ignore", "forbid")
)

Arguments

.name

The class's name, as a single string.

...

Named fields, one type each.

.description

The JSON Schema "description" for schema(), or NULL to omit it.

.parent

An S7 class to inherit from, or NULL. Its properties are inherited as typed fields.

.extra

"forbid" rejects unknown keys when parsing a list into the class; the default "ignore" drops them.

Value

An S7 class.

Details

Unlike struct(), the name is not registered, so ref() and opt("Name") will not resolve it: a name in that registry means something that builds instances, and this builds S7 objects. Pass the class itself instead – it is a value, and a type.

See also

as_s7_class() to convert an existing struct, struct() for the plain-list equivalent.

Examples

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

  Account <- s7_struct("Account",
    id     = int[1][. > 0],
    email  = chr[1][grepl("@", ., fixed = TRUE)],
    credit = num[1][. >= 0] %default% 0
  )

  a <- Account(id = 1, email = "ada@example.org")
  a@credit

  a@credit <- 10L   # coerced to double, exactly as rdantic would
  typeof(a@credit)

  try(a@id <- 0)
  try(Account(id = 1))

  # it is a type, so it parses, validates and describes itself
  from_json(Account, '{"id": 2, "email": "bob@example.org"}')
  schema(Account)$required

  Premium <- s7_struct("Premium", tier = one_of("gold", "silver"),
                       .parent = Account)
  S7_inherits(Premium(id = 1, email = "a@b.org", tier = "gold"), Account)
}
#> Error : 1 validation problem in <Account>
#>   @id  expected int[1][. > 0], got num[1] 0
#> Error : 1 validation problem in <Account>
#>   @email  expected chr[1][grepl("@", ., fixed = TRUE)], got <missing>
#> [1] TRUE