CFFI Pass callback as parameter to another function

Question

Here is an explanation of my misunderstanding:

I have a class named Codex:

class Codex:
    ffi = FFI()
    def __init__(self):
        self.ffi = FFI()
        self.ClibDec = self.ffi.dlopen("...")
        self.ffi.cdef("""int CRD_Set(int handle, int property, void *value);
                         int CRD_Get(int handle, int property, void *value);
                      """)

    def funct1(self):
        handle = self.ClibDec."something"
        self.ClibDec.CRD_Set(handle, 0, funct2)

    @ffi.callback("int(*)(int, int)")
    def funct2(self, handle):

        status = 0
        self.ClibDec.CRD_Get(handle, 420, status)
        # do something

        return 0

My question is how can I call funct2 inside self.ClibDec.CRD_Set in my funct1 ?

I check several similar issues and the doc: https://cffi.readthedocs.io/en/latest/using.html#callbacks-old-style

But I still not understand the usage of callback (old style)

Answer 1

Maybe you are looking for code like this? This would be the solution closest to what you're trying to write.

class MyClass:

    def funct1(self):
        handle = self.ClibDec."something"
        # make a cdata function pointer object that will call
        # back self.funct2(handle)
        cfnptr = ffi.callback("int(*)(int)", self.funct2)
        self.ClibDec.CRD_Set(handle, 0, cfnptr)
        # the cfnptr pointer must not be called after
        # the variable 'cfnptr' goes out of scope,
        # which occurs when funct1() returns here.

    def funct2(self, handle):
        ...
        return 0