AWS step function: Use nested variable inside condition

Question

I am are trying to write a step function where each function.

Let's say this is the output of one of the function is

{ 
    ...
    "foo": {
      "1": "one"
      "2": "two", 
      "5": "five"
     },
    "current": 2
    ...
}

I have a choice statement, which needs to check what is the value of test_key and dereference it in foo dictionary.

...
"ChoiceState": {
      "Type" : "Choice",
      "Choices": [
        {
          "Variable": "$.foo['$.current']",  <--- This is unsupported
          "StringEquals": "two",
          "Next": "TwoFunction"
        }, 
        {
          "Variable": "$.foo['$.current']",  <--- This is unsupported
          "StringEquals": "three",
          "Next": "ThreeFunction"
        }
        ...
      ],
      "Default": "DefaultFunction"
    }
...

How do I use dynamic reference in choice states?

adamwong · Accepted Answer · 2021-01-05 08:01:07Z

1

JSONPath doesn't support dynamic keys so this isn't possible. You have to restructure your input data or combine multiple Choice Rules with the And comparison operator to check the corresponding property based on current:

{
  "And": [
    {
      "Variable": "$.current",
      "StringEquals": "2"
    },
    {
      "Variable": "$.foo.2",
      "StringEquals": "two"
    }
  ],
  "Next": "TwoFunction"
}

answered Jan 5, 2021 at 8:01

adamwong

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