Discuss the drawback of using const IParametersHandler in the Advanceable class

[GiulioRomualdi]

In #267 I added

bool initialize(std::shared_ptr<const BipedalLocomotion::ParametersHandler::IParametersHandler>)

method.

The signature of the method is in theory fine since a block should not change the handler in the initialization phase, however, in practice, this creates several issues.

For instance, in centroidal-mpc-walking I tried to instantiate the LeggedOdometry however I'm not able to do it because the LeggedOdometry::initialize() wants a non-const IParameterHandler.
https://github.com/dic-iit/bipedal-locomotion-framework/blob/4ad31d8d62ffa0e3da5b7fbef77a945124c7bb4e/src/Estimators/include/BipedalLocomotion/FloatingBaseEstimators/FloatingBaseEstimator.h#L160-L161

Here two possible solutions can be implemented:

1. Change the signature of
   https://github.com/dic-iit/bipedal-locomotion-framework/blob/4ad31d8d62ffa0e3da5b7fbef77a945124c7bb4e/src/Estimators/include/BipedalLocomotion/FloatingBaseEstimators/FloatingBaseEstimator.h#L160-L161
   Into bool initialize(std::weak_ptr<const BipedalLocomotion::ParametersHandler::IParametersHandler> handler, std::shared_ptr<iDynTree::KinDynComputations> kindyn);
2. Implement the copy constructor/copy assignment operator for IParameterHandler.

This first solution is temporary since we may need to expand the content of a ParameterHandler and if the object is const this is not possible.
On the other hand, I don't know how to implement the second solution. Since there is no way to get the type of a stored parameter is almost impossible to copy the content of a parameter handler into another one. (e.g. I don't know how to copy the content of a YarpParameterHandler in a StdParameterHandler and vice-versa)

cc @prashanthr05 @S-Dafarra and @traversaro

[S-Dafarra]

I would go for the first solution. I would prefer if the user of the parameters handler does not modify anything.

[GiulioRomualdi]

I would go for the first solution. I would prefer if the user of the parameters handler does not modify anything.

I agree with that however we may need to change the content of the handler in the future. For instance, several classes require the sampling_time and the user may specify it only once. e.g.

sampling_time 0.01

[IK]
some_useful_parameter "parameter"

if the ik requires the sampling time in c++ we need to expand the parameter handler used in the ik with sampling_time. This is currently not possible

void initilizeIK(std::shared_ptr<const IParameterHandler> handler, double samplingTime)
{
    auto newHandler = std::make_shared<StdParameterHandler>();
    newHandler->set(handler); //<---------------- This is not possible
    newHandler->setParameter("sampling_time", samplingTime);
   ...........
}

[S-Dafarra]

Ok, we need a method to clone then 🤔 I think that is doable for both the implementations we have at the moment.
Something like

virtual std::shared_ptr<IParameterHandler> IParameterHandler::clone() const = 0;

[GiulioRomualdi]

You are right!

[GiulioRomualdi]

#288 implements what @S-Dafarra suggested in #285 (comment)

Before closing the issue we should address point 1 of #285 (comment)