A form from properties

A row that names a property instead of a control does not need a control, a label, or a value: the builder makes the control from the property's metadata, labels it from the metadata, and binds it to the property.

Track track = getSharedContext().get(Track.class, 1L);

FormBuilder fb = new FormBuilder(cp);
fb.property(track, Track_.name()).control();
fb.property(track, Track_.composer()).control();
fb.property(track, Track_.unitPrice()).control();
fb.property(track, Track_.genre()).control();

• What the four lines did
• Naming the property
• Overriding what the metadata says
• readOnly and disabled
• The rest of the chain

What the four lines did

control() with no argument is what asks for a control to be made. For each row, the builder

• reads the property's metadata - Track.name is a mandatory String of 200 characters whose label is "Title", Track.unitPrice is money, Track.genre is a relation to another entity,
• asks the ControlCreatorRegistry for the control that fits it, which is a Text2<String> for the first, a Text2<BigDecimal> with a money converter for the third and a LookupInput2<Genre> for the last,
• labels it with the property's label and marks it mandatory when the property is,
• and binds the control's value to that property of that instance.

Which control comes out of which property is decided by the registry and is described with the controls themselves - see text and value input and metadata. The binding is the ordinary data binding: typing in the box changes the Track instance, and changing the instance changes the box.

Naming the property

fb.property(track, Track_.name()).control();          // the generated QField
fb.property(track, "name").control();                 // by name

The QField form is the one to use: Track_ is generated from the entity, so a renamed property is a compile error rather than a runtime one, and the chain knows the property's type - which is what lets control(control) check that the control fits the property. See typed properties.

Naming the property as a String gives a chain that does not know the type: it takes any IControl, and it is the chain that has converter() on it, because the converter cannot be checked against the property's type either way.

In Kotlin a property reference does the same as the QField:

fb.property(track, Track::name).control()

Overriding what the metadata says

fb.property(track, Track_.composer()).label("A label of my own").control();
fb.property(track, Track_.unitPrice()).mandatory().hint("What the shop charges").control();
fb.property(track, Track_.genre()).control(ComboLookup2.class);
fb.property(track, Track_.name()).label("A control of my own").control(ownControl);

Every step of the chain overrules the metadata for that one row.

readOnly and disabled

Both can be set outright, bound to a property, or set for a run of rows:

FormBuilder fb = new FormBuilder(cp);
fb.readOnlyAll(this, "locked");                       // from here on: bound to page.locked
fb.property(track, Track_.name()).control();
fb.property(track, Track_.composer()).control();
fb.readOnlyAllClear();                                // and no longer
fb.property(track, Track_.unitPrice()).control();

The row wins over the builder: a readOnly() on the row is used even when readOnlyAll() is in force. The bound forms are ordinary bindings, so the control follows the property as it changes - tick the box on the demo page above and the two controls under it become read only while the third does not.

disabledBecause() disables the control and says why, which the control shows as its tooltip. It is set on the control's own disabledBecause property; a control that has no such property is simply disabled.

The rest of the chain