Schema: Schema class

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

Schema class

Description

A model of a schema with helpful methods for working with the schema and supported data. Schema instances can be initialized with a schema source as a url to a JSON file or a JSON object. The schema is initially validated (see validate). By default validation errors will be stored in $errors but in a strict mode it will be instantly raised.

Usage

# Schema.load(descriptor, strict=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

Format

R6Class object.

Value

Object of R6Class .

Methods

Schema$new(descriptor = descriptor, strict = strict)

Use Schema.load to instantiate Schema class.

getField(name)

Get schema field by name.

• name String with schema field name.

• (Field/NULL) Returns Field instance or NULL if not found.

addField(descriptor)

Add new field to schema. The schema descriptor will be validated with newly added field descriptor.

• descriptor List of field descriptor.

• TableSchemaError Raises any error occured in the process.

• (Field/NULL) Returns added Field instance or NULL if not added.

removeField(name)

Remove field resource by name. The schema descriptor will be validated after field descriptor removal.

• name String with schema field name.

• TableSchemaError Raises any error occured in the process.

• (Field/NULL) Returns removed Field instances or NULL if not found.

castRow(row)

Cast row based on field types and formats.

• row Data row as a list of values.

• (any) Returns cast data row.

infer(rows, headers=1)

Cast row based on field types and formats.

• rows List of lists representing rows.

• headers data sample headers, one of:

  • row number containing headers (rows should contain headers rows)

  • list of headers (rows should NOT contain headers rows)

• {Object} Returns Table Schema descriptor.

commit(strict)

Cast row based on field types and formats.

• strict Boolean, alter strict mode for further work.

• TableSchemaError Raises any error occured in the process.

• (Boolean) Returns TRUE on success and FALSE if not modified.

save(target)

Cast row based on field types and formats.

• target String, path where to save a descriptor.

• TableSchemaError Raises any error occured in the process.

• (Boolean) Returns TRUE on success.

Properties

valid

Returns validation status. It always TRUE in strict mode.

errors

Returns validation errors. It always empty in strict mode.

descriptor

Returns list of schema descriptor.

primaryKey

Returns string list of schema primary key.

foreignKeys

Returns list of schema foreign keys.

fields

Returns list of Field instances.

fieldNames

Returns a list of field names.

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

Schema.load, Table Schema Specifications

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