Using shared_pointer in classes?

[helloworld135]

solved

[JLBorges]

The design problem that you are facing is not quite clear. Perhaps, you are looking for CRTP?
https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern

Something along these lines?

#include <memory>

struct A
{
    using pointer = std::shared_ptr<A> ;

    A( int ii = 0 ) : i(ii) {}
    // ..
    int i ;
};

struct B
{
    using pointer = std::shared_ptr<B> ;
    // ..
};

template < typename DERIVED > struct C
{
    using pointer = std::shared_ptr<C> ;

    C( int ss = 0 ) : s(ss) {}
    virtual ~C() = default ;
    C( const C& ) = default ;
    C( C&& ) = default ;
    C& operator= ( const C& ) = default ;
    C& operator= ( C&& ) = default ;

    static C<DERIVED>::pointer fun( A::pointer pa1, A::pointer pa2 )
    { return std::make_shared<DERIVED>( pa1->i + pa2->i ) ; }

    virtual B::pointer test() = 0 ;

    // ...

    int s = 0 ;
};

struct func1 : C<func1>
{
    using C<func1>::C ;

    virtual B::pointer test() override { return std::make_shared<B>() ; }
};

[ne555]

I have no idea what you are trying to solve, what approach did you chose or what problem do you have implementing it.
Be a little more descriptive, we are not aware of your situation.

Also, learn terminology.


> a class that has a bunch of shared pointers like this
you haven't show any member variable.

> Inside Class A I have another shared_pointer typedef,
¿why is that relevant?

> I also need to pass two shared_pointers into this function
¿which function? `test()' does not take any parameters.
Also, ¿why is that a problem?

> and the typedef is also a shared function
typedef is not a function

> I'm confused on how to use the shared pointers or how to pass them into this
> new class
like you do in any other case.


Also, would recommend to use another name for your class, one that doesn't clash with the name of its functions.

[helloworld135]

solved

[ne555]

Again, ¿what problem are you trying to solve?


> class BothTrue : public Gates
`BothTrue is the name of an static member function. It may lead to confusion if you you are refering to the constructor or to the function.

    State out() const override
    {
        return out;
    }

¿how different would be the other overloads? ¿couldn't you move this to the parent?

BothTrue(InputPoint c, InputPoint d)
    {
      //How can I convert the inputs above to take them as arguments below?
        if(c==true && d==true)

Not sure what you are asking here.
you may use `c' and `d' inside that constructor as you like. If you want to compare c against true, then no idea, I do not know what that class does, what is its purpose or how is it made (perhaps c.numberpriv == State::On)

[helloworld135]

solved

[ne555]

if( c->number()==State::On and d->number()==State::On )


> class BothTrue is a subclass of class Gate.
and function BothTrue is an static member function of class Gate.
¿have you implemented that?

looking here http://www.cplusplus.com/forum/beginner/179691/

I'm trying to make a pure virutal method. So I added virtual class 1 function(); to the bottom of my third class, and I made all the members static.

¿why did you "made all the members static"?
¿do you know what static means?

[helloworld135]

solved

[ne555]

Let me see if I understand, you are trying to simulate a logic circuit.

class Gates
{
	public:
		virtual State out() const = 0;
		virtual ~Gates() = default; //needed because there is a virtual member function
};

that's the whole `Gates' class.
Note that `Gates' it is not aware of any subclasses that it may have, adding new subclasses require no modification to `Gates'.
The only operation that can perform on a gate is to query its output, that function would be overloaded on the derived classes.

class BothTrue /*aka And*/: public Gates{
public:
	BothTrue(Input a, Input b); //a binary gate, it has two inputs
	State out() const override{
		return
			a->number() == State::On //number() seems to be a bad name
			and b->number() == State::On;
	}
private:
	Input a, b; //it needs to store those inputs to be able to operate on them later
};

BothTrue::BothTrue(Input a, Input b): //constructor
	a(a), //initialization list
	b(b)
{}


//another subclass
class Anyone /*aka Or*/: public Gates{
public:
	Anyone(Input a, Input b); //again, a binary gate
	State out() const override{
		return
			a->number() == State::On
			or b->number() == State::On;
	}

private:
	Input a, b;
}

//yet another one
class Opposite /*aka Not*/: public Gates{
public:
	Opposite(Input a); //unary gate
	State out() const override{
		return
			a->number() == State::Off;
	}
private:
	Input a;
}

//one more
class JustOne /*aka Xor*/: public Gates{
public:
	JustOne(Input a, Input b):
	//just pseudo, you'll need std::make_shared
		result(
			Input(
				BothTrue( //~AB
					Input(Opposite(a)),
					b
				),
			),
			Input(
				BothTrue( //A~B
					a,
					Input(Opposite(b)
				)
			)
		)
	{}

	State out() const override{
		return result->out();
	}
		
private:
	Anyone result; //would implement ~AB + A~B
}

last one is only to show composition, but the result was hideous.


Edit: I forgot about the typedef, it should be `InputPoint' instead of just `Input' in the constructor and member variables.

[helloworld135]

solved

[ne555]

I don't see why it may give you that error message.
`.number()' returns a State and State::On is a State, ¿right?

You shouldn't cast away your error, ¿can upload your project to github or similar so we can take a look at it?

[helloworld135]

solved

[ne555]

The error was on the return. `.out()' should return a `State' but was trying to return a bool.

//for Opposite
if(a->number() == State::Off)
   return State::On;
else
   return State::Off;

I'll recommend you to make a function to convert from bool to State

Here's a sample https://github.com/ne555/gates

[helloworld135]

Thanks, ne555!

[ne555]

IMO, you want to shoot an ant that it's standing on your foot.
`BothTrue' already has a meaning as a class, then you want to use a function with a suspicious similar name to return a pointer to that same class.

BothTrue(a, b); //an object
Gate::BothTrue(a, b); //a pointer 

If you do it as an static member function, the problem is that objects of that class may call the method

Anyone foo(a, b);
foo.BothTrue(a,b); //¿? 

If you really want to do it, perhaps a namespace

//gates_hidden.h
/*this classes are not mean to be used directly*/
typedef std::shared_ptr<Gate_> GatePoint;
class Gate_{ //note the underscore
   //...
};
class BothTrue_: public Gate_{
   //...
};
//...


//gates.h
#include "gates_hidden.h"
namespace Gate{
   inline GatePoint BothTrue(InputPoint a, InputPoint b){
      return std::make_shared<BothTrue_>(a, b);
   }
}

Then if you later want to add another gate kind

class Foo_: public Gate_{ //again, not used directly
   //...
};

namespace Gate{
   inline GatePoint Foo(InputPoint a, InputPoint b, InputPoint c){
      return std::make_shared<Foo>(a, b, c);
   }
}

didn't put much thought on it, there may be a better way.