Good OOP design for solver with modern Fortran

I am developing Fortran code to solve a PDE system.

The way it is being developed now is that I have a type Variablethat has several attributes, the most important of which is an array valthat stores the value.

Now I also have a class solverthat will do the calculations on Variable. I decided that passing the whole to the Variablesolver and working with it variable%valevery time I want to start it (several thousand times during the exectution) would be inefficient, so I decided to define the pointer fields in solverto bind the solver to the corresponding variable. for instance

program example
    use variable
    use solvers

    type(Variable) T 
    type(Solver) solver_temperature

    !Contructors
    call T%create()
    call solver_temperature%create(T)

    call solver_temperature%solve()
end program example

And solver module

module solvers
type Solver
    real*8, pointer :: T(:,:)

contains 
    procedure :: create
    procedure :: solve
end type

contains
    subroutine create(this,T)
        type(Solver) :: this
        type(Variable) :: T

        this%T => T%val
    end subroutine
end module

, , .

, , ? . T solve ? ?