Have I split up these Constructs incorrectly?

Question

I'm fairly new to CDK and I've tried migrating something from vanilla JavaScript to TypeScript, in doing so trying to make it a little more modular. This is the current structure that I've got:

CdkStack.ts

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

    // API Gateway
    const api = new API(scope, "API");
}

Api.ts

export class API extends Construct {
    public restApi: RestApi;

    constructor(scope: Construct, id: string) {
        super(scope, id);

        const restApi = new RestApi(this, "website-api", {
            restApiName: "website-api",
            description: "This service provides API calls for the website.",
        });

        const getListLambda = new GetListLambda(
            scope,
            "GetListLambda"
        );

        const listApi = restApi.root.addResource("list");
        listApi.addMethod("GET", getListLambda.integration); // GET /
    }
}

GetListLambda.ts

export class GetListLambda extends Construct {
    public lambdaFunction: Function;
    public integration: LambdaIntegration;

    constructor(scope: Construct, id: string) {
        super(scope, id);

        this.lambdaFunction = new Function(this, "GetListLambda", {
            runtime: Runtime.NODEJS_12_X,
            code: new AssetCode("lambdas/getList", {
                exclude: ["*.local.js", "*.test.js"],
            }),
            handler: "index.handler",
            environment,
        });

        this.integration = new LambdaIntegration(this.lambdaFunction, {
            proxy: true,
        });
    }
}

I used to have basically the same code, but all in a single file. With this current structure I get the following output when I try to do a deploy:

No stack could be identified for the construct at path API/website-api

/src/api/node_modules/@aws-cdk/aws-apigateway/lib/restapi.ts:540 if (this.methods.length === 0) { ^ TypeError: Cannot read property 'length' of undefined at RestApi.validate (/src/api/node_modules/@aws-cdk/aws-apigateway/lib/restapi.ts:540:22) at RestApi.onValidate (/src/api/node_modules/@aws-cdk/core/lib/construct-compat.ts:97:17) at Node.validate (/src/api/node_modules/constructs/lib/construct.ts:445:54) at Node.validate (/src/api/node_modules/constructs/lib/construct.ts:442:45) at Node.validate (/src/api/node_modules/constructs/lib/construct.ts:442:45) at Node.synthesize (/src/api/node_modules/constructs/lib/construct.ts:391:27) at Function.synth (/src/api/node_modules/@aws-cdk/core/lib/construct-compat.ts:231:22) at App.synth (/src/api/node_modules/@aws-cdk/core/lib/app.ts:142:36) at process. (/src/api/node_modules/@aws-cdk/core/lib/app.ts:121:45) at Object.onceWrapper (events.js:422:26)

The error reads as though there aren't any methods, however I've clearly added a method to the API.

Should you be using const api = new API(this, "API"); instead, to pass down the reference to the stack for the underlying modules? — dmahapatro
@dmahapatro that might well be the problem! Thanks. You might want to add an answer — Ian

dmahapatro dmahapatro · Accepted Answer · 2020-06-07T14:46:55

Using

const api = new API(this, "API");

instead of

const api = new API(scope, "API");

will pass down the stack reference to the underlying modules.

Have I split up these Constructs incorrectly?

1 Answers