IndexableProperty

The IndexableProperty is a helper (proxy) object to obtain a scalar component from a material property. Use it in objects that process a scalar quantity instead of a Real material property to allow the user to supply any material property of a type from the list below along with a component index parameter to select a scalar component from the property value.

To use this utility class declare a member in your class header

const IndexableProperty<Parent, is_ad> _prop;

where Parent is the current class' parent class. IndexableProperty provides a helper method to add the default parameters for coupling a material property (property) and its component index (component). Use it as follows

InputParameters params = IndexableProperty<Parent, is_ad>::validParams();

This also adds the Parent class parameters to params. You may also choose to add your own parameters of type MaterialPropertyName and std::vector<unsigned int> with custom names and documentation strings.

params.addRequiredParam<MaterialPropertyName>("first_property",
                                              "The name of the first material property");
params.addRequiredParam<MaterialPropertyName>("second_property",
                                              "The name of the second material property");
params.addParam<std::vector<unsigned int>>(
    "first_component", "Index of the component of the first property");
params.addParam<std::vector<unsigned int>>(
    "second_component", "Index of the component of the second property");

To initialize the IndexableProperty object put

  _prop(this)

in your objects initializer list. If you chose custom names for the property name and component parameters, pass them in as the second and third arguments, like so

  _first_prop(this, "first_property", "first_component")
  _second_prop(this, "second_property", "second_component")

An IndexableProperty object can be implicitly cast to bool to check if _any_ of the supported indexable properties was found.

if (!_prop)
  paramError("property", "No suitable material property was found");