schema.load: Instantiate 'Schema' class

In frictionlessdata/tableschema-r: Table Schema 'Frictionless Data'

Instantiate Schema class

Description

Factory method to instantiate Schema class. This method is async and it should be used with value keyword from future package.

Usage

Schema.load(descriptor, strict=FALSE, caseInsensitiveHeaders = FALSE)

Arguments

descriptor	schema descriptor, a JSON string, URL or file
strict	flag to alter validation behaviour: if FALSE error will not be raised and all error will be collected in schema$errors if TRUE any validation error will be raised immediately
caseInsensitiveHeaders	default is set to FALSE

Value

Schema class object

See Also

Schema, Table Schema Specifications

Examples

SCHEMA <- '{"fields": [
  {"name": "id", "type": "string", "constraints": {"required": true}},
  {"name": "height", "type": "number"},
  {"name": "age", "type": "integer"},
  {"name": "name", "type": "string", "constraints": {"required": true}},
  {"name": "occupation", "type": "string"}
  ]}'

# instantiate Schema class
def  = Schema.load(descriptor = SCHEMA)
schema = future::value(def)

# correct number of fields
length(schema$fields)

# correct field names
schema$fieldNames

# convert row
row = list('string', '10.0', '1', 'string', 'string')
castRow = schema$castRow(row)
castRow

SCHEMA_MIN <- '{
"fields": [
  {"name": "id"},
  {"name": "height"}
  ]}'

# load schema
def2  = Schema.load(descriptor = SCHEMA_MIN)
schema2 = future::value(def2)
  
# set default types if not provided
schema2$fields[[1]]$type
schema2$fields[[2]]$type

# fields are not required by default
schema2$fields[[1]]$required
schema2$fields[[2]]$required


#work in strict mode
descriptor = '{"fields": [{"name": "name", "type": "string"}]}'
def3  = Schema.load(descriptor = descriptor, strict = TRUE)
schema3 = future::value(def3)
schema3$valid

# work in non-strict mode
descriptor = '{"fields": [{"name": "name", "type": "string"}]}'
def4 = Schema.load(descriptor = descriptor, strict = FALSE)
schema4 = future::value(def4)
schema4$valid

# work with primary/foreign keys as arrays
descriptor2 = '{
"fields": [{"name": "name"}],
"primaryKey": ["name"],
"foreignKeys": [{
  "fields": ["parent_id"],
  "reference": {"resource": "resource", "fields": ["id"]}
}]}'

def5 = Schema.load(descriptor2)
schema5 = future::value(def5)

schema5$primaryKey
schema5$foreignKeys


# work with primary/foreign keys as string
descriptor3 = '{
"fields": [{"name": "name"}],
"primaryKey": "name",
"foreignKeys": [{
  "fields": "parent_id",
  "reference": {"resource": "resource", "fields": "id"}
}]}'

def6 = Schema.load(descriptor3)
schema6 = future::value(def6)
schema6$primaryKey
schema6$foreignKeys

frictionlessdata/tableschema-r documentation built on Oct. 1, 2022, 11:44 a.m.