parse_ast: Parse AST

In gqlr: 'GraphQL' Server in R

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)

Example output

function (obj, schema) 
{
    if (inherits(obj, "Date")) {
        (function (obj, schema) 
        {
            as.Date(obj)
        })(obj$value, schema)
    }
    else {
        NULL
    }
}
<environment: namespace:gqlr>
function (obj, schema) 
{
    if (inherits(obj, "IntValue")) {
        (function (value, ...) 
        {
            MAX_INT <- 2147483647
            MIN_INT <- -2147483648
            num <- suppressWarnings(as.integer(value))
            if (!is.na(num)) {
                if (num <= MAX_INT && num >= MIN_INT) {
                  return(num)
                }
            }
            return(NULL)
        })(obj$value, schema)
    }
    else {
        NULL
    }
}
<environment: namespace:gqlr>

gqlr documentation built on Dec. 2, 2019, 5:07 p.m.