CFD Online Discussion Forums - Error when <dictionary>.lookup("variable"). OpenFOAM 1.6-ext

I'm making my owen solver from icoFoam, where I add a body force B = U0m*(2*pi/period)*cos((2*pi/period)*t).
Where the period and free stream velocity (U0m) is to be loaded fra a dictionary. I think I have figured out the syntax from looking in "createFields.H" to keep it simple I started with the assumption that the variables was gonna be placed in "transportProperties".

Code:

IOdictionary transportProperties

(

    IOobject

    (

        "transportProperties",

         runTime.constant(),

         mesh,

         IOobject::MUST_READ,

         IOobject::NO_WRITE

    )

);



scalar period(transportProperties.lookup("period"));

scalar U0m(transportProperties.lookup("U0m"));

added the last two lines, but when I try to make the solver i get the following error:

Code:

createFields.H: In function 'int main(int, char**)':

createFields.H:20: error: cannot convert 'Foam::ITstream' to 'Foam::scalar' 

createFields.H:21: error: cannot convert 'Foam::ITstream' to 'Foam::scalar' in initialization

Additional questions

What is good practice, shall I add min variables (period,U0m) in the transportPorperties or make an additional dictionary?
I need the variables to be of class scalar, what is the syntax in the dictionary? is it as that of an dimensionedScalar omitting the dimension array:

Code:

period period 9.72;