Field {tableschema.r} | R Documentation |
Field class
Description
Class represents field in the schema.
Data values can be cast to native R types. Casting a value will check the value is of the expected type, is in the correct format, and complies with any constraints imposed by a schema.
Usage
# Field$new(descriptor, missingValues = list(""))
Arguments
descriptor |
Schema field descriptor |
missingValues |
A list with vector strings representing missing values |
base_path |
see description |
strict |
see description |
value |
see description |
constraints |
see description |
... |
see description |
Format
R6Class
object.
Details
A field descriptor MUST
be a JSON object that describes a single field.
The descriptor provides additional human-readable documentation for a field,
as well as additional information that may be used to validate the field or
create a user interface for data entry.
The field descriptor object
MAY
contain any number of other properties.
Some specific properties are defined below. Of these, only the name
property is REQUIRED
.
name
-
The field descriptor
MUST
contain aname
property. This propertySHOULD
correspond to the name of field/column in the data file (if it has a name). As such itSHOULD
be unique (though it is possible, but very bad practice, for the data file to have multiple columns with the same name).name
SHOULD NOT
be considered case sensitive in determining uniqueness. However, since it should correspond to the name of the field in the data file it may be important to preserve case. title
-
A human readable label or title for the field.
description
-
A description for this field e.g. "The recipient of the funds".
Value
Object of R6Class
.
Methods
Field$new(descriptor, missingValues = list(""))
-
Constructor to instantiate
Field
class.
descriptor
Schema field descriptor.missingValues
A list with vector strings representing missing values.TableSchemaError
Raises any error occured in the process.Field
ReturnsField
class instance.
cast_value(value, constraints=TRUE)
-
Cast given value according to the field type and format.
value
Value to cast against fieldconstraints
Gets constraints configuration: it could be set to true to disable constraint checks, or it could be a List of constraints to checkerrors$TableSchemaError
Raises any error occured in the processany
Returns cast value
testValue(value, constraints=TRUE)
-
Test if value is compliant to the field.
value
Value to cast against fieldconstraints
Constraints configurationBoolean
Returns if value is compliant to the field
Properties
name
Returns field name
type
Returns field type
format
Returns field format
required
Returns
TRUE
if field is requiredconstraints
Returns list with field constraints
descriptor
Returns field descriptor
Language
The key words MUST
, MUST NOT
, REQUIRED
, SHALL
, SHALL NOT
,
SHOULD
, SHOULD NOT
, RECOMMENDED
, MAY
, and OPTIONAL
in this package documents are to be interpreted as described in RFC 2119.
See Also
Field Descriptors Specifications
Examples
DESCRIPTOR = list(name = "height", type = "number")
field <- Field$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)