Get the ObjCIvarDecl

clang::ObjCIvarDecl *getIvarDeclOrNull(clang::ObjCPropertyRefExpr *prop) {
  // the simple case, it is an explicitproperty and that points us to the ivardecl
  if(prop->getExplicitProperty() && prop->getExplicitProperty()->getPropertyIvarDecl())
    return prop->getExplicitProperty()->getPropertyIvarDecl();

  // the more complicated case...
  // find the corresponding ValueDecl to the Base of the ObjCPropertyRefExpr
  // when the ValueDecls type is a ObjCInterfaceDecl and clang knows the interface-implementation
  // we iterate over all property-implementations and compare their names with the name of the
  // getter-selector
  if(clang::ImplicitCastExpr *base= dyn_cast_or_null<clang::ImplicitCastExpr>(prop->getBase())) {
    if(clang::DeclRefExpr *d= dyn_cast_or_null<clang::DeclRefExpr>(base->getSubExpr())) {
      clang::ValueDecl *val= d->getDecl();
      if(val->getType()->isObjCObjectPointerType()) {
        clang::ObjCInterfaceDecl *iface= val->getType()->getAsObjCInterfacePointerType()->getInterfaceDecl();
        if(iface && iface->getImplementation()) {
          clang::ObjCImplementationDecl *impl= iface->getImplementation();
          for(clang::ObjCImplementationDecl::propimpl_iterator i= impl->propimpl_begin(); i!= impl->propimpl_end(); ++i) {
            // does the property know which ivar it belongs to and does the ivar has the same name as the requested property?
            if((*i)->getPropertyIvarDecl() && (*i)->getPropertyIVarDecl()->getNameAsString()== prop->getGetterSelector().getAsString())
              return (*i)->getPropertyIvarDecl(); // match of the ivar to the corresponding property-getter
          }
        }
      }
    }
  }
  return 0;
}