apps apps apps

1-app-is-your-app.ts

// Simple case, my "app" is just a stack
const app = new cdk.App();
new MyStack(app, 'MyFrobulizerConsumer');

//---------------------------------------------------------------------------

// More complex case, my "app" is a subclass of App because it contains multiple
// stacks and I can organize them
new MyApp('TweetFrobulizer');

//---------------------------------------------------------------------------

// Instantiating multiple apps or the same app multiple times
new MyApp('TweetFrobulizerEU', { ... });
new MyApp('TweetFrobulizerUS', { ... });
new OpTools('TweetFrobulizerTools');

2-app-is-cdk-construct.ts

// Simple case, my "app" is just a stack
// ==> This is the same
const app = new cdk.App();
new MyStack(app, 'MyFrobulizerConsumer');

//---------------------------------------------------------------------------

// More complex case

// I still need to instantiate a boilerplate thing that has nothing to 
// do with *MY* code
const app = new cdk.App();   

new MyApp(app, 'TweetFrobulizer');

//---------------------------------------------------------------------------

// Instantiating multiple apps or the same app multiple times

// Again, this boilerplate thing is here
const app = new cdk.App();   

new MyApp(app, 'TweetFrobulizerEU', { ... });
new MyApp(app, 'TweetFrobulizerUS', { ... });
new OpTools(app, 'TweetFrobulizerTools');



// So the difference as I see it is in the simple case, we can retcon that
// the App you instantiate is actually *your* app, and we can hide the 
// machinery of coming up with a proper (shared) Root instance inside that class.
//
// Whereas in the other scenario, you HAVE to instantiate that Root object,
// but it's obviously framework machinery sticking out.
//
// Now the downsides of making users subclass App is that:
// 1) The signature will be slightly different from construct, which will be
//    confusing.
// 2) Their stuff isn't as obviously reusble as when it was a cdk.Construct.
//
// Mitigations for making the `App` class stick out like that:
// 1) Rename it? But to what?
// 2) Static singleton accessor? But named what? Probably shouldn't involve
// the word "root" anywhere or we're going to get back into tree building
// discussions that we don't want to have.

const host = new cdk.Host();

// or

const model = new cdk.AppModel();

// or

new MyStack(cdk.Host.root, 'MyStack');

new MyStack(cdk.App.appScope, 'MyStack');