TypeScript: strongly typed lookup function

[paralin]

I'm finding myself doing this a lot:

(<any>tree.lookup('mynamespace.MyMessage')).encode...

The reason is that lookup returns a ReflectionObject which I cannot directly cast to any of its children (I can cast a Type -> ReflectionObject but not the other way around).

I'm proposing doing something like:

tree.lookupService('mynamespace.MyService'); // ok -> ProtoBuf.Service
tree.lookupType('mynamespace.MyService'); // throws -> MyService is not a Type

Strongly typed with exceptions if you attempt to lookup the wrong type (or just return null)

[dcodeIO]

Hmm, the following is passing in the test file:

protobuf.Class.create(root.lookup("Hello") as protobuf.Type, Hello);

[paralin]

It's possible, but messy. And not particularly safe (in the case that it isn't in fact a Type)

[bb]

The changeset 01365ba helps specifically for Type and Service, but if I understand @paralin correctly, he was looking for a type declaration like

lookup<T>(path: (string|string[]), parentAlreadyChecked?: boolean): T extends (ReflectionObject|Type);

(didn't check that, just trying to generalize the type definition right here in the comment editor)

This would enable him writing

tree.lookup<MyMessage>('mynamespace.MyMessage').encode...

[paralin]

Actually @bb that's not what I meant, however what you have posted is quite nice and I'd love it if that was in place.

[dcodeIO]

I'd favor any solution that doesn't require additional code (like it is now with lookupType etc.), and just works on a definition basis. I added the additional functions as there doesn't seem to be a clean way, but if there is, I'll gladly change it.

[xujihui1985]

Hi @dcodeIO, I tested the following on node v6.9.1, and seems nodejs doesn't happy with that https://github.com/dcodeIO/protobuf.js/blob/master/types/test.ts#L20

it throws error TypeError: Cannot assign to read only property 'prototype' of function on
https://github.com/dcodeIO/protobuf.js/blob/master/src/class.js#L44 , because property prototype on constructor is not writeable while the clazz is an Class

[dcodeIO]

Try "typescript": "^2.2.0-dev.20161214",

[dcodeIO]

lookupType and lookupService are now generated programmatically, which makes me feel a lot better about this. Considering this issue fixed for now.