Field | R Documentation |
Class representing a field in the schema.
Data values can be cast to native R types. Casting a value checks whether it is of the expected type, in the correct format, and compliant with any constraints imposed by the schema.
# Field$new(descriptor, missingValues = list(""))
descriptor |
Schema field descriptor. |
missingValues |
A list with vector strings representing missing values. |
R6Class
object.
A field descriptor MUST
be a JSON object that describes a single field. The descriptor provides both human-readable documentation and machine-readable validation rules. It may also guide user interface generation for data entry.
The descriptor object
MAY
include additional custom properties. Of these, only the name
property is REQUIRED
.
name
The descriptor MUST
contain a name
property, typically corresponding to the column name in the data file. This name SHOULD
be unique, and while not case-sensitive for uniqueness, preserving case is advisable.
title
A human-readable label for the field.
description
A text description of the field, e.g., "The recipient of the funds".
Object of class R6Class
.
Field$new(descriptor, missingValues = list(""))
Constructor to instantiate the Field
class. Accepts the following arguments:
descriptor
Schema field descriptor.
missingValues
A list of strings representing missing values.
TableSchemaError
Raised if an error occurs during instantiation.
Field
Returns a Field
class instance.
cast_value(value, constraints = TRUE)
Casts a given value according to the field's type and format.
value
Value to cast.
constraints
Logical or list of constraints to apply.
errors$TableSchemaError
Raised if casting fails due to a constraint violation.
any
Returns the cast value.
testValue(value, constraints = TRUE)
Tests if a value complies with the field definition.
value
Value to test.
constraints
Constraints configuration.
Boolean
Returns TRUE
if the value is compliant.
name
Returns the field name.
type
Returns the field type.
format
Returns the field format.
required
Returns TRUE
if the field is required.
constraints
Returns a list of field constraints.
descriptor
Returns the field descriptor.
The key words MUST
, MUST NOT
, REQUIRED
, SHALL
, SHALL NOT
, SHOULD
, SHOULD NOT
, RECOMMENDED
, MAY
, and OPTIONAL
in this documentation are to be interpreted as described in RFC 2119.
Field Descriptors Specifications
DESCRIPTOR = list(name = "height", type = "number")
field <- Field$new(descriptor = DESCRIPTOR)
# get correct instance
field$name
field$format
field$type
# return true on test
field$testValue(1)
# cast value
field$cast_value(1)
# expand descriptor by defaults
field <- Field$new(descriptor = list(name = "name"))
field$descriptor
# parse descriptor with "enum" constraint
field <- Field$new(descriptor = list(name = "status", type = "string",
constraints = list(enum = list('active', 'inactive'))))
field$testValue('active')
field$testValue('inactive')
field$testValue('activia')
field$cast_value('active')
# parse descriptor with "minimum" constraint'
field <- Field$new(descriptor = list(name = "length", type = "integer",
constraints = list(minimum = 100)))
field$testValue(200)
field$testValue(50)
# parse descriptor with "maximum" constraint'
field <- Field$new(descriptor = list(name = "length", type = "integer",
constraints = list(maximum = 100)))
field$testValue(50)
field$testValue(200)
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