PathParser

Builds a Projection Expression that can be used to filter the returned attributes of a read operation like a GetItem, Query or Scan:

import { PathParser } from 'dynamodb-toolbox/entity/actions/parsePaths'

// 👇 To be used in DynamoDB commands
const { ProjectionExpression, ExpressionAttributeNames } =
  PokemonEntity.build(PathParser)
    .parse(['name', 'level'])
    .toCommandOptions()

Methods

parse(...)

(paths: Path<ENTITY>[]) => PathParser

Parses a list of paths. Throws an invalidExpressionAttributePath error if a path is invalid:

PokemonEntity.build(PathParser).parse(['name', 'level'])

Note that the parse method should only be used once per instance (for now). See Building Paths for more details on how to write paths.

toCommandOptions()

() => CommandOptions

Collapses the PathParser state to a set of options that can be used in a DynamoDB command:

const { ProjectionExpression, ExpressionAttributeNames } =
  PokemonEntity.build(PathParser)
    .parse(['name', 'level'])
    .toCommandOptions()

setId(...)

(id: string) => ConditionParser

Adds a prefix to expression attribute keys. Useful to avoid conflicts when using several expressions in a single command:

PokemonEntity.build(PathParser)
  .parse(['name', 'level'])
  .toCommandOptions()
// => {
//   ProjectionExpression: '#p_1, #p_2',
//   ExpressionAttributeNames: {
//     '#p_1': 'name',
//     '#p_2': 'level'
//   }
// }

PokemonEntity.build(PathParser)
  .setId('0')
  .parse(['name', 'level'])
  .toCommandOptions()
// => {
//   ProjectionExpression: '#p0_1, #p0_2',
//   ExpressionAttributeNames: {
//     '#p0_1': 'name',
//     '#p0_2': 'level'
//   }
// }

Paths

The path syntax from DynamoDB-Toolbox follows the DynamoDB specifications, while making it type-safe and simpler:

import type {
  Path,
  PathIntersection
} from 'dynamodb-toolbox/entity/actions/parsePaths'

type PokemonPath = Path<typeof PokemonEntity>

const namePath: PokemonPath = 'name'

const deepListPath: PokemonPath = 'pokeTypes[0]'

const deepMapOrRecordPath: PokemonPath = 'weaknesses.fire'
// 👇 Similar to
const deepMapOrRecordPath: PokemonPath = `weaknesses['fire']`

// 👇 Use this syntax to escape special chars (e.g. in `records`)
const deepRecordPath: PokemonPath = `meta['any[char]-you.want!']`

// Path common to both entities
type PokemonAndTrainerPath = PathIntersection<
  [typeof PokemonEntity, typeof TrainerEntity]
>
const commonPath: PokemonAndTrainerPath = 'name'