Choice workflow state

A Choice state ("Type": "Choice") adds conditional logic to a state machine.

In addition to most of the common state fields, Choice states contains the following additional fields.

Choice Rules (JSONata)

A Choice state must have a Choices field whose value is a non-empty array of Choice Rules, which contain the following fields when using JSONata:

The following example checks whether the numerical value is equal to 1.

{
  "Condition": "{% $foo = 1 %}",
  "Next": "NumericMatchState"
}

The following example checks whether the typevariable is equal to local.

{
  "Condition": "{% $type = 'local' %}",
  "Next": "StringMatchState"
}

The following example checks whether the string is greater than MyStringABC.

{
  "Condition": "{% $foo > 'MyStringABC' %}",
  "Next": "StringGreaterMatchState"
}

The following example checks whether the string is not null.

{
 "Condition" : "{% $possiblyNullValue != null and $possiblyNullValue = 42 %}",
 "Next": "NotNullAnd42"
}

Choice Rules (JSONPath)

A Choice state must have a Choices field whose value is a non-empty array of Choice Rules, which contain the following fields when using JSONPath:

The following example checks whether the numerical value is equal to 1.

{
  "Variable": "$.foo",
  "NumericEquals": 1,
  "Next": "FirstMatchState"
}

The following example checks whether the string is equal to MyString.

{
  "Variable": "$.foo",
  "StringEquals": "MyString",
  "Next": "FirstMatchState"
}

The following example checks whether the string is greater than MyStringABC.

{
  "Variable": "$.foo",
  "StringGreaterThan": "MyStringABC",
  "Next": "FirstMatchState"
}

The following example checks whether the string is null.

{
 "Variable": "$.possiblyNullValue",
 "IsNull": true
}

The following example shows how the StringEquals rule is only evaluated when $.keyThatMightNotExist exists because of the preceding IsPresent Choice Rule.

"And": [
 {
 "Variable": "$.keyThatMightNotExist",
 "IsPresent": true
 },
 {
 "Variable": "$.keyThatMightNotExist",
 "StringEquals": "foo"
 }
]

The following example checks whether a pattern with a wildcard matches.

{
 "Variable": "$.foo",
 "StringMatches": "log-*.txt"
}

The following example checks whether the timestamp is equal to 2001-01-01T12:00:00Z.

{
  "Variable": "$.foo",
  "TimestampEquals": "2001-01-01T12:00:00Z",
  "Next": "FirstMatchState"
}

The following example compares a variable with another value from the state input.

{
 "Variable": "$.foo",
 "StringEqualsPath": "$.bar"
}

Step Functions examines each of the Choice Rules in the order listed in the Choices field. Then it transitions to the state specified in the Next field of the first Choice Rule in which the variable matches the value according to the comparison operator.

The following comparison operators are supported:

For each of these operators, the corresponding value must be of the appropriate type: string, number, Boolean, or timestamp. Step Functions doesn't attempt to match a numeric field to a string value. However, because timestamp fields are logically strings, it's possible that a field considered to be a timestamp can be matched by a StringEquals comparator.