Manipulate the selected input using the Parameters filter - Amazon Step Functions
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Manipulate the selected input using the Parameters filter

While the InputPath filter helps you limit the raw JSON input you provide, using the Parameters filter, you can pass a collection of key-value pairs as input. These key-value pairs can either be static values that you define in your state machine definition, or values that are selected from the raw input using InputPath.

In your workflows, Parameters are applied after InputPath. Parameters help you specify how the underlying task accepts its input payload. For example, if the check-address Lambda function accepts a string parameter as input instead of the JSON data, you can use the Parameters filter to transform the input.

In the following example, the Parameters filter receives the input you selected using InputPath in Step 3: Use the InputPath filter to select specific parts of an execution input and applies the intrinsic function States.Format on the input items to create a string called addressString. Intrinsic functions help you perform basic data processing operations on a given input. For more information, see Intrinsic functions.

"Parameters": { "addressString.$": "States.Format('{}. {}, {} - {}', $.street, $.city, $.state, $.zip)" }

Consequently, the following string gets created and is provided to the check-address Lambda function as input.

{ "addressString": "123 Main St. Columbus, OH - 43219" }