open fun <C : StringFormControl> addCustom(key: KProperty1<K, Any?>, control: C, required: Boolean = false, requiredMessage: String? = null, legend: String? = null, validatorMessage: ((C) -> String?)? = null, validator: ((C) -> Boolean?)? = null): FormPanel<K>
Adds a string control to the form panel bound to custom field type.
key - key identifier of the control
control - the string form control
required - determines if the control is required
requiredMessage - optional required validation message
legend - put this control inside a fieldset with given legend
validatorMessage - optional function returning validation message
validator - optional validation function
Return
current form panel