(aws-cdk-lib.Fn): Support Fn::ForEach

[faridnsh]

Describe the feature

Fn::ForEach is a new function that is added to cloudformation.

Use Case

Creating multiple resources based on Cloudformation template parameter. I'm deploying CDK generated templates to Service Cataloge.

Proposed Solution

ForEach function in aws-cdk-lib.Fn

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

v2.96.2

Environment details (OS name and version, etc.)

Any

[pahud]

Thank you for the feature request and PR! This is an awesome feature!

[faridnsh]

Giving this more thoughts, we'll have to think off how the interface would be. This could be applied to resources, conditions and outputs.

[faridnsh]

Here's two different possibilities, we could create resources for it:

1. Inside a callback function, which makes it somewhat functional programming looking:

    new ForEach(this, 'Queues', queueNames, (scope: Construct, variable: string)  => {
        new sqs.Queue(scope, 'Test', {
            queueName: Token.asString(variable)
        })
    });

2. Or use the class properties:

    const forEach = new ForEach(this, 'Queues', queueNames);
    new sqs.Queue(forEach.childrenScope, 'Test', {
      queueName: Token.asString(forEach.identifier)
    });

It would be nice to gather more input from CDK core members.

[matheushent]

This feature request is open for quite a while... any prevision on when it is coming?

[erikrj]

This is a feature we would really like to see. We have stacks that fetch parameters in remote regions using an AwsCustomResource and we want to be able to do Fn.split and then Fn.forEach to loop over them when CloudFormation executes.

[matheushent]

This is such a key to our business nowadays. It would be good if this gets prioritized. For us, we want to iterate over a parameter whose type is a list

[jaecktec]

hey @faridnsh , I personnally am in favour of the first suggestion. It feels more typescripty and less yamlish.

[matheushent]

hey @faridnsh , I personnally am in favour of the first suggestion. It feels more typescripty and less yamlish.

The first suggestion is indeed more typescripty and that's precisely why it shouldn't be implemented that way. We have to note that CDK is used in many languages, and, IMO, it should have a good experience in all of them :)

[automartin5000]

This is a feature we would really like to see. We have stacks that fetch parameters in remote regions using an AwsCustomResource and we want to be able to do Fn.split and then Fn.forEach to loop over them when CloudFormation executes.

Have the same use case