Reference to static member function & inheritance

Question

I'm using libuv in a C++ program. I have two classes, A and B that inherit from C.

I use libuv and declared an instance of uv_signal_t on C. Creating an instance of uv_signal_t requires a callback to be passed. I can easily pass a lambda to the C function to go around the problem of references to static member functions:

const int32_t r = uv_signal_start(&this->signal, [](uv_signal_t *handle, int signum){}, SIGABRT);

But how can I provide a different implementation of the callback on each child class? Ideally I'd have some common code implemented on C.cpp and additional code on each child.

Update

To be clear, I cannot change the signature of the callback method, as it's defined by libuv. I could edit the source for libuv, but I'm not sure I want to go that deep.

score 0 · Accepted Answer · answered Jan 26 '15 at 20:26

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I'll add a function pointer as a property to my class C and implement it as necessary on the derived classes. More here.

answered Jan 26 '15 at 20:26

ruipacheco

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Min Lin · Answer 2 · 2015-01-26T16:32:09.143

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I think you can capture this pointer in the lambda, and call a virtual function through this. The virtual function can be overrided in derived classes then.

 const int32_t r = uv_signal_start(&this->signal, [this](uv_signal_t *handle, int signum){ return this->callback(); }, SIGABRT);

edited Jan 26 '15 at 16:32

answered Jan 26 '15 at 00:49

Min Lin

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error: 'this' cannot be implicitly captured in this context – ruipacheco Jan 26 '15 at 10:36
then capture explicitly. – Min Lin Jan 26 '15 at 16:30
I can't change the signature of the lambda. – ruipacheco Jan 26 '15 at 16:34
I don't think capture is part of signature of the closure. – Min Lin Jan 26 '15 at 16:40
Btw, uv_xxx_t has a data field, you can set it to this, that's the usual way to pass data. – Min Lin Jan 26 '15 at 16:43
Won't I be overwriting any data sets data to? – ruipacheco Jan 26 '15 at 18:15
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/69623/discussion-between-lapinrigolo-and-min-lin). – ruipacheco Jan 26 '15 at 18:33
As libuv was a wrapper to libev on Linux, there is no data field in libev, you need to make your own by inheriting the handle. Data is introduced in libuv for your convenience to put custom data. That's what it meant for. – Min Lin Jan 26 '15 at 20:52

Reference to static member function & inheritance

2 Answers2