mvvmfx/src/main/java/de/saxsys/mvvmfx/utils/mapping/ModelWrapper.java
public StringProperty field(String identifier, StringPropertyAccessor<M> accessor) {
		return addIdentified(identifier, new FxPropertyField<>(this::propertyWasChanged, accessor,
				() -> new SimpleStringProperty(null, identifier)));
	}
public StringProperty field(String identifier, StringPropertyAccessor<M> accessor) {
		return addIdentified(identifier, new FxPropertyField<>(this::propertyWasChanged, accessor,
				() -> new SimpleStringProperty(null, identifier)));
	}
Add a new field of type String to this instance of the wrapper. See {@link #field(StringPropertyAccessor)}. This
method additionally takes a string identifier as first parameter.

This identifier is used to return the same property instance even when the method is invoked multiple times.

@param identifier
an identifier for the field.

@param accessor
a function that returns the property for a given model instance. Typically you will use a method
reference to the javafx-property accessor method.
@return The wrapped property instance.