CODEWITHSUNDEEP
c++functionparameters
xcaliph
xcaliph

Reputation: 3

Using variables to store custom functions in a class

I'm trying to make a class with some member variables that store or point to functions, or can be assigned a different behaviour which describe how to process other variables in the object.

class C {
    int n;
    void *data;
    // buidData: It allocates and stores data using the data pointer avobe to be processed later
    // processData: It does something with n and data

    public:
    void run(); //performs processData 
    // setters needed...

}

Here, buildData and processData could be just methods that do one thing: Maybe buildData allocates memory for a double and processData stores n^3 in the allocated position.

What I need for them is to be variables: some function-type variable, or function pointer which can somehow be assigned a code describing its behavior. So, instead of just calculating n^3 always, it could perhaps build a random list of n elements that removes duplicates when the process function is run, store a file name read from console and process a file with that name or... pretty much anything (or nothing at all).

So, in concept, I want empty methods whose behavior I can borrow easily using previously existing code in a parametric fashion.

I strongly feel C++ is giving me the tools to do it (lambda functions, function pointers, the function type in <functional>...) but for some months I didn't get there yet.

How can I possibly declare buildData and processData and how should one assign them their "job" in an elegant way?

Upvotes: 0

Views: 237

Answers (1)

0x5453
0x5453

Reputation: 13599

Sounds like you are looking for std::function. You can assign default functions in the same way that you might assign default values to primitive members, but then override the functions in C's constructor if necessary.

Alternatively, you could go with the classic OOP solution where C is a base class with default behaviors, but users are allowed to extend into a child class that overrides the behavior for buildData and processData.

Upvotes: 3

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