View source for Contrib/IOReferencer

'''IOReferencer''' allows you to retrieve non-IOobjects through the [[OpenFOAM_guide/objectRegistry|objectRegistry]].  [http://www.cfd-online.com/Forums/openfoam/88823-objectregistry-lookupobject-scalar.html Inspired by this thread.]


{{VersionInfo}}{{Version1.5}}{{Version1.5-dev}}{{Version1.6}}{{Version1.6-ext}}{{Version1.7.0}}{{Version1.7.1}}{{Version1.7.x}}{{Version2.0.0}}

== Why do you need it? ==
OpenFOAM organizes its model-related data into a database, known as the [[OpenFOAM_guide/objectRegistry|objectRegistry]].  This database is used to share data between the solver and its components, such as boundary conditions, discretization schemes, and thermophysical models.  This is accomplished with the ever-so-useful <tt>lookupObject</tt> function.

For example, say you are writing a custom viscosity model and you want to use the local temperature.  You would write:
<cpp>    const volScalarField& T = db().lookupObject<volScalarField>("T");
    // The "db()" above may vary
</cpp>

And you now have temperature.  The problem is: not all objects are supported by the [[OpenFOAM_guide/objectRegistry|objectRegistry]].  Say you want to look up a scaling factor that you defined in your solver, e.g.: <tt>scalar lengthScale;</tt> but you can't seem to use <tt>lookupObject</tt> on scalars.  That's because only ''"IOobjects"'' are supported by the [[OpenFOAM_guide/objectRegistry|objectRegistry]].

'''IOReferencer''' solves this problem, allowing any non-IOobject can be looked up through the [[OpenFOAM_guide/objectRegistry|objectRegistry]].

== How do you use it? ==
In the code that ''creates'' the non-IOobject, '''before''':

<cpp>    scalar myObject(1.12 /*or some other expression*/);
</cpp>

In the code that ''creates'' the non-IOobject, '''after''':

<cpp>#include "IOReferencer.H"

    scalar myObject(1.12 /*or some other expression*/);

    // Once you've declared your non-IOobject, make its referencer:
    IOReferencer<scalar> myObjectRef
    (
        IOobject
        (
            "lookupName",
            runTime.constant(), /*can be anything*/
            runTime,            /*can be anything*/
            IOobject::NO_READ,  /*must be NO_READ*/
            IOobject::NO_WRITE  /*must be NO_WRITE*/
        ),
        myObject
    );
</cpp>

In the code that wants to look it up:

<cpp>    const scalar& myObject = db().lookupObject<IOReferencer<scalar> >
    (
        "lookupName"
    )();
    // Note: the db() bit may be different, depending on which object you are in.
</cpp>

and you have a <tt>const</tt> reference to your non-IOobject.

A coupled of notes:

* The ''referencer'' (e.g. <tt>myObjectRef</tt> above) and the object itself (e.g. <tt>myObject</tt> above) should be declared one after the other; and
* When the referencer or object itself go out of scope, the entry is removed from the objectRegistry... so make sure they stay in scope when you want to use them.

== How to install it ==
<ol>
<li> Download and unpack or checkout by using one of the following possibilities:

<ul>
<li>Using SVN:
<bash>svn checkout svn://svn.code.sf.net/p/openfoam-extend/svn/trunk/Breeder_1.6/libraries/IOReferencerObject IOReferencerObject</bash>
</li>

<li>Using Git-SVN:
<bash>git svn clone svn://svn.code.sf.net/p/openfoam-extend/svn/trunk/Breeder_1.6/libraries/IOReferencerObject IOReferencerObject</bash>
</li>

<li>Using Git (from an unofficial mirror repository):
<bash>git clone https://github.com/Unofficial-Extend-Project-Mirror/openfoam-extend-Breeder1.6-libraries-IOReferencerObject.git \
  IOReferencerObject</bash>
</li>

<li>Using {{tt|wget}} (from an unofficial mirror repository):
<bash>wget -O IOReferencerObject.tar.gz \
  "https://github.com/Unofficial-Extend-Project-Mirror/openfoam-extend-Breeder1.6-libraries-IOReferencerObject/archive/master.tar.gz"</bash>
Then unpack it by running:
<bash>tar xzvf IOReferencerObject.tar.gz \
  --transform='s/openfoam-extend-Breeder1.6-libraries-IOReferencerObject-master/IOReferencerObject/'</bash>
</li>
</ul>
</li>

<li>Copy the directory <tt>IOReferencer</tt> to <tt>src/OpenFOAM/db/IOobjects</tt></li>
<li>From <tt>src/OpenFOAM</tt>, execute these commands:
<bash>rm -rf lnInclude
wmakeLnInclude .</bash>
</li>
</ol>

You are done.  No compiling or anything is required.  Enjoy!

== Update info ==
* ''2011-08-11'': Initial import

[[User:Marupio|Marupio]] 17:37, 13 August 2011 (CEST)