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lbilli / rib

An R implementation of Interactive Brokers API
GNU General Public License v3.0
34 stars 7 forks source link

How to modify callback methods #4

Closed ashannon closed 5 years ago

ashannon commented 5 years ago

Hello,

First, let me thank you for creating this package. It is very well written and seems to be truly feature complete, which is great.

Alas, i have a problem. I am trying to modify the IBWrapSimple class to include more complex logic with respect to the various callback methods (mostly tickPrice and tickSize). I have tried creating a new class by copy pasting the source code and making modifications to it, and then instantiating a new wrapper object from that new class. This works well for the most part, except when the checkMsg() calls marketDataType() which then calls map_int2enum(), which cannot be found. It appears to only be visible within the rib namespace, which my new copy pasted version of the class can’t see.

I tried modifying the IBWrapSimple class this way as the public methods in the objects instantiated by IBWrapSimple were blocked. Is there a way to unblock them?

More generally, what would be the preferred approach to modifying callback methods without affecting the behaviour of the rib package?

Thank you,

AS

lbilli commented 5 years ago

In general you can only use functions that a package explicitly exports, i.e. those listed in NAMESPACE. However, you can still access unexported functions by using the ::: notation.

In this case, map_int2enum() is not currently exported, but you can use it in your own code like this:

rib:::map_int2enum(...)

So, if you cut-and-paste code from within the package, you need to prepend rib::: to unexported functions.

ashannon commented 5 years ago

That is a good suggestion. Thank you for the quick reply.

AS