Loading schemas with SchemaLoader

Schemas define the object types and structure of the database. See Object schemas for detailed information about schemas in ZooDb.

import { SchemaLoader } from '@phfaist/zoodb/schemaloader';

class SchemaLoader()

Load schema object data from a collection of YAML or JSON source files, and dereference any { "$ref": ... } internal and external references.

Configuration options:

• schemas - an object with the following properties:

  • schemas.schema_root - a filesystem path or URL where to look for schemas.

  • schemas.schema_rel_path - a relative path to prefix any schema name that we might want to look up. It will be interpreted as a path relative to the schema_root.

  • schemas.schema_add_extension - a filename extension to add to the bare schema name when looking up the schema. E.g. ‘.json’ or ‘.yml’.

  Example:

  schemas: {
      schema_root: 'https://errorcorrectionzoo.org/',
      schema_rel_path: '/schemas/',
      schema_add_extension: '.json',
  }
  

• schema_names - a list of names of schemas to load for the zoo database. If null or undefined and the schema_root is a filesystem path, then the corresponding directory contents is inspected and files matching the given schema_add_extension are loaded as schemas.

• fs - the filesystem access handle. We need the method readFile() for any requested filesystem paths. We also need the readdir() method if schema_names is null or undefined.

See also makeStandardYamlDbDataLoader() for a simplified loading.

SchemaLoader.SchemaLoader

SchemaLoader.load_schema_by_name(schema_name)

Load and return a single schema by name, dereferencing any $ref references. Repeated calls for the same name return the cached result without re-reading the file.

This method allows loading an additional schema that is not listed in the constructor’s schema_names config — for example, a supplementary schema needed at runtime.

Arguments:

• schema_name (string) – The bare schema name (without path prefix or file extension) corresponding to a file under the configured schema_root / schema_rel_path.

Throws:

Error – If the file cannot be read, parsed, or dereferenced.

Returns:

Promise.<Object> – The resolved JSON Schema object.

SchemaLoader.load_schemas()

Load all schemas specified by the schema_names config property (or, when schema_names is null, by listing all matching files in the schema root directory) and return an object { schemas } whose schemas property maps each schema name to its resolved JSON Schema object.

Each referenced $ref within a schema is dereferenced automatically. The returned schemas object may be passed directly to ZooDb.load_data().

Throws:

Error – If schema_names is null but schema_root is not a file: URL, or if any schema file cannot be read or parsed.

Returns:

Promise.<{schemas: Object}> –