parse_ast {gqlr}

Parse AST

Description

This is a helper function for Scalars. Given a particular kind and a resolve function, it produces a function that will only parse values of a particular kind.

Usage

parse_ast(kind, resolve)

Arguments

kind

single character name of a class to parse

resolve

function to parse the value if the kind is correct

Details

Typically, kind is the same as the class of the Scalar. When making a new Scalar, parse_ast defaults to use the name of the scalar and the scalar's parse value function.

This function should only need to be used when defining a schema in gqlr_schema()

Value

function that takes obj and schema that will only parse the value if the kind is inherited in the obj

Examples

parse_date_value <- function(obj, schema) {
  as.Date(obj)
}
parse_ast("Date", parse_date_value)

# Example from Int scalar
parse_int <- function(value, ...) {
  MAX_INT <-  2147483647
  MIN_INT <- -2147483648
  num <- suppressWarnings(as.integer(value))
  if (!is.na(num)) {
    if (num <= MAX_INT && num >= MIN_INT) {
      return(num)
    }
  }
  return(NULL)
}
parse_ast("IntValue", parse_int)