BusLine | 仿《车来了》公交线路自定义View，根据线路数据绘制View并控制滑动手势。

Not clear what the actual logic of the desired output is, but this works:

Find the 3 smallest values in your dataframe (using numpy):

You have two related problems here.

The first is that if you are doing asynchronous calls, your handler must return a Promise. Otherwise the library does not know when the asynchronous call is done, has the data, and you can send back a reply.

Since you are making an HTTP call, this is an async request, and thus needs to be done using a Promise. The easiest way to do this is to use the request-promise-native package instead of the request package.

So that part of the code might look something like this:

The problem is that you are checking if the list out is null:

If you want to express any transportation with any vehicle with any engine, then you want 3 boxes, each talking in terms of the "previous" type-erased wrappers. You don't want generic placeholders on any of these boxes, as you want to talk in terms of fully heterogenous instances (e.g not any transportation with a specific Vehicle type, or any vehicle with a specific Motor type).

Furthermore, rather than using a class hierarchy to perform the type erasing, you can use closures instead, which allows you to capture the base instance rather than storing it directly. This allows you to remove a significant amount of the boilerplate from your original code.

For example: