# Choice

Define a Choice in the state machine.

A choice state can be used to make decisions based on the execution
state.

Extends: Construct › State › Choice
Implements: IChainable, IConstruct, IDependable

- Source: [`aws-stepfunctions/lib/states/choice.ts`](https://github.com/aws/aws-cdk/blob/v2.274.0/packages/aws-cdk-lib/aws-stepfunctions/lib/states/choice.ts#L33)
- Type last changed: v2.178.0 · 6 Feb 2025

## Example

```ts
const map = new sfn.Map(this, 'Map State', {
  maxConcurrency: 1,
  itemsPath: sfn.JsonPath.stringAt('$.inputForMap'),
  itemSelector: {
    item: sfn.JsonPath.stringAt('$$.Map.Item.Value'),
  },
  resultPath: '$.mapOutput',
});

// The Map iterator can contain a IChainable, which can be an individual or multiple steps chained together.
// Below example is with a Choice and Pass step
const choice = new sfn.Choice(this, 'Choice');
const condition1 = sfn.Condition.stringEquals('$.item.status', 'SUCCESS');
const step1 = new sfn.Pass(this, 'Step1');
const step2 = new sfn.Pass(this, 'Step2');
const finish = new sfn.Pass(this, 'Finish');

const definition = choice
    .when(condition1, step1)
    .otherwise(step2)
    .afterwards()
    .next(finish);

map.itemProcessor(definition);
```

## Initializer

```ts
new Choice(scope: Construct, id: string, props?: ChoiceProps)
```

## Construct Props

- `assign`: { [key: string]: any } — Workflow variables to store in this step.

  **Default:** Not assign variables

  Using workflow variables, you can store data in a step and retrieve that data in future steps.

- `comment`: string — A comment describing this state.

  **Default:** No comment

- `inputPath`: string = $ — JSONPath expression to select part of the state to be the input to this state.

  May also be the special value JsonPath.DISCARD, which will cause the effective
  input to be the empty object {}.

- `outputPath`: string = $ — JSONPath expression to select part of the state to be the output to this state.

  May also be the special value JsonPath.DISCARD, which will cause the effective
  output to be the empty object {}.

- `outputs`: any — Used to specify and transform output from the state.

  **Default:** $states.result or $states.errorOutput

  When specified, the value overrides the state output default.
  The output field accepts any JSON value (object, array, string, number, boolean, null).
  Any string value, including those inside objects or arrays,
  will be evaluated as JSONata if surrounded by {% %} characters.
  Output also accepts a JSONata expression directly.

- `queryLanguage`: [QueryLanguage](/cdk/api/v2/docs/aws-cdk-lib.aws_stepfunctions.QueryLanguage.html) = JSONPath — The name of the query language used by the state.

  If the state does not contain a `queryLanguage` field,
  then it will use the query language specified in the top-level `queryLanguage` field.

- `stateName`: string — Optional name for this state.

  **Default:** The construct ID will be used as state name

## Properties

- `endStates`: [INextable](/cdk/api/v2/docs/aws-cdk-lib.aws_stepfunctions.INextable.html)[] (required) — Continuable states of this Chainable.

- `id`: string (required) — Descriptive identifier for this chainable.

- `node`: [Node](/cdk/api/v2/docs/constructs.Node.html) (required) — The tree node.

- `startState`: [State](/cdk/api/v2/docs/aws-cdk-lib.aws_stepfunctions.State.html) (required) — First state of this Chainable.

- `stateId`: string (required) — Tokenized string that evaluates to the state's ID.

## Methods

- `addPrefix(x: string): void` — Add a prefix to the stateId of this state.

- `afterwards(options?: AfterwardsOptions): Chain` — Return a Chain that contains all reachable end states from this Choice.

  Use this to combine all possible choice paths back.

- `bindToGraph(graph: StateGraph): void` — Register this state as part of the given graph.

  Don't call this. It will be called automatically when you work
  with states normally.

- `filterNextables(states: State[]): INextable[]` (static) — Return only the states that allow chaining from an array of states.

- `findReachableEndStates(start: State, options?: FindStateOptions): State[]` (static) — Find the set of end states states reachable through transitions from the given start state.

- `findReachableStates(start: State, options?: FindStateOptions): State[]` (static) — Find the set of states reachable through transitions from the given start state.

  This does not retrieve states from within sub-graphs, such as states within a Parallel state's branch.

- `isConstruct(x: any): boolean` (static) — Checks if `x` is a construct.

  Use this method instead of `instanceof` to properly detect `Construct`
  instances, even when the construct library is symlinked.

  Explanation: in JavaScript, multiple copies of the `constructs` library on
  disk are seen as independent, completely different libraries. As a
  consequence, the class `Construct` in each copy of the `constructs` library
  is seen as a different class, and an instance of one class will not test as
  `instanceof` the other class. `npm install` will not create installations
  like this, but users may manually symlink construct libraries together or
  use a monorepo tool: in those cases, multiple copies of the `constructs`
  library can be accidentally installed, and `instanceof` will behave
  unpredictably. It is safest to avoid using `instanceof`, and using
  this type-testing method instead.

  **Parameters**

  - `x` — Any object.

  **Returns:** true if `x` is an object created from a class which extends `Construct`.

- `jsonata(scope: Construct, id: string, props?: ChoiceJsonataProps): Choice // chainable` (static) — Define a Choice using JSONata in the state machine.

  A choice state can be used to make decisions based on the execution
  state.

- `jsonPath(scope: Construct, id: string, props?: ChoiceJsonPathProps): Choice // chainable` (static) — Define a Choice using JSONPath in the state machine.

  A choice state can be used to make decisions based on the execution
  state.

- `otherwise(def: IChainable): Choice // chainable` — If none of the given conditions match, continue execution with the given state.

  If no conditions match and no otherwise() has been given, an execution
  error will be raised.

- `prefixStates(root: IConstruct, prefix: string): void` (static) — Add a prefix to the stateId of all States found in a construct tree.

- `toStateJson(topLevelQueryLanguage?: QueryLanguage): json` — Return the Amazon States Language object for this state.

- `toString(): string` — Returns a string representation of this construct.

- `when(condition: Condition, next: IChainable, options?: ChoiceTransitionOptions): Choice // chainable` — If the given condition matches, continue execution with the given state.

- `with(...mixins: IMixin[]): IConstruct` — Applies one or more mixins to this construct.

  Mixins are applied in order. The list of constructs is captured at the
  start of the call, so constructs added by a mixin will not be visited.
  Use multiple `with()` calls if subsequent mixins should apply to added
  constructs.

  **Parameters**

  - `mixins` — The mixins to apply.

  **Returns:** This construct for chaining