What problem does ecs TagParameterContainerImage solve?

[dleavitt]

I've read through the docs,
both here: https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_ecs.TagParameterContainerImage.html
and here: https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codepipeline_actions-readme.html#deploying-ecs-applications-stored-in-a-separate-source-code-repository

And I'm a little confused as to what problem this construct solves.

Why do this (use TagParameterImage):

export class PipelineStack extends Stack {
  public readonly tagParameterContainerImage: ecs.TagParameterContainerImage;

  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const appEcrRepo = new ecr.Repository(this, "EcsDeployRepository");
    this.tagParameterContainerImage = new ecs.TagParameterContainerImage(
      appEcrRepo,
    );

    new codepipeline.Pipeline(this, "CodePipelineDeployingEcsApplication", {
      // elided...
      stages: [
        {
          stageName: "Deploy",
          actions: [
            new codepipeline_actions.CloudFormationCreateUpdateStackAction({
              // elided...
              parameterOverrides: {
                [this.tagParameterContainerImage.tagParameterName]:
                  appCodeBuildAction.variable("imageTag"),
              },
            }),
          ],
        },
      ],
    });
  }
}

export class EcsAppStack extends Stack {
  constructor(scope: Construct, id: string, props: EcsAppStackProps) {
    super(scope, id, props);

    const taskDefinition = new ecs.TaskDefinition(this, 'TaskDefinition');
    taskDefinition.addContainer('AppContainer', {
      image: props.image,
    });
  }
}

const app = new App();

const pipelineStack = new PipelineStack(app, 'PipelineStack');
new EcsAppStack(app, 'AppStack', {
  image: pipelineStack.tagParameterContainerImage,
});

When you can just do this (use a CfnParameter):

export class PipelineStack extends Stack {
  repo: ecr.IRepository;

  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    this.repo = new ecr.Repository(this, "EcsDeployRepository");

    new codepipeline.Pipeline(this, "CodePipelineDeployingEcsApplication", {
      // elided...
      stages: [
        {
          stageName: "Deploy",
          actions: [
            new codepipeline_actions.CloudFormationCreateUpdateStackAction({
              // elided...
              parameterOverrides: {
                ImageTagParam: appCodeBuildAction.variable("imageTag"),
              },
            }),
          ],
        },
      ],
    });
  }
}

export class EcsAppStack extends Stack {
  constructor(scope: Construct, id: string, props: EcsAppStackProps) {
    super(scope, id, props);

    const dockerTagParam = new CfnParameter(this, "ImageTagParam");
    const image = ecs.ContainerImage.fromEcrRepository(
      props.repo,
      this.dockerTagParam.valueAsString,
    );

    const taskDefinition = new ecs.TaskDefinition(this, "TaskDefinition");
    taskDefinition.addContainer("AppContainer", { image: image });
  }
}

const app = new App();

const pipelineStack = new PipelineStack(app, "PipelineStack");
new EcsAppStack(app, "AppStack", { repo: pipelineStack.repo });

Is the construct doing anything that's important?