mvvmfx/src/main/java/de/saxsys/mvvmfx/utils/mapping/ModelWrapper.java
public StringProperty field(String identifier, StringGetter<M> getter, StringSetter<M> setter) {
		return addIdentified(identifier, new BeanPropertyField<>(this::propertyWasChanged, getter, setter,
				() -> new SimpleStringProperty(null, identifier)));
	}
public StringProperty field(String identifier, StringGetter<M> getter, StringSetter<M> setter) {
		return addIdentified(identifier, new BeanPropertyField<>(this::propertyWasChanged, getter, setter,
				() -> new SimpleStringProperty(null, identifier)));
	}
Add a new field of type String to this instance of the wrapper. See {@link #field(StringGetter, StringSetter)}.
This method additionally takes a string identifier as first parameter.
<p/>
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 getter
a function that returns the current value of the field for a given model element. Typically you will
use a method reference to the getter method of the model element.
@param setter
a function that sets the given value to the given model element. Typically you will use a method
reference to the setter method of the model element.
@return The wrapped property instance.