How to pass variables/outputs from CloudFormationCreateUpdateStackAction to next stages?

Question

This is PreProdApplicationStack, it has a output exportName: "Url". I want to access this output/variable after CloudFormation deployment stage. 
```tsx
...
this.url = new CfnOutput(this, `Url`, {
      description: "api url",
      exportName: `Url`,
      value: api.url,
    });
```

This is deployPreProd action 
```tsx
const deployPreProd =
      new aws_codepipeline_actions.CloudFormationCreateUpdateStackAction({
        actionName: "DeployPreProdApplication",
        templatePath: cdkBuildOutput.atPath(
          "PreProdApplicationStack.template.json"
        ),
        stackName: "PreProdApplicationStack",
        adminPermissions: true,
        variablesNamespace: "PreProdVariables",
        outputFileName: "PreProdOutputs",
        output: preProdOutput,
      });
```

Then I want to to access variables/outputs from the deployed template in a build action 
```tsx
// build action
    const integtestBuildAction = new aws_codepipeline_actions.CodeBuildAction({
      environmentVariables: {
        SERVICE_URL: {
          value: "HOW TO ACCESS VARIABLES/OUTPUTS from deployPreProd?",
        },
      },
      actionName: "IntegTest",
      project: integtestCodeBuild,
      input: sourceOutput,
    });
```

Answer

CDK has a `Fn.importValue` method you can use to access exported values: https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Fn.html - it should help if the stack that has the exported value exists and is in the same region as your calling stack.

Answer

Yes, I mentioned in my first reply that importValue requires

> the stack that has the exported value exists and is in the same region as your calling stack

If the stack hasn't been created the outputs won't exist.

It may be possible to pass the value of `api.url` directly if this is all in one CDK app, by creating stack properties that you pass to the stack that requires them, but I don't know from the info you've given if `api.url` will be synthesised at that point.

It may be (again, hard to know without seeing all your code) that the solution you have arrived at is the only one that will work in your case, as you can only access the exported value after the stack that exports it has been created.

Answer

Have you tried the following?
```
import * as cdk from 'aws-cdk-lib';

// build action
    const integtestBuildAction = new aws_codepipeline_actions.CodeBuildAction({
      environmentVariables: {
        SERVICE_URL: {
          value: cdk.Fn.importValue('Url'),
        },
      },
```

How to pass variables/outputs from CloudFormationCreateUpdateStackAction to next stages?

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