Entity Events

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Lanzamiento	Modificaciones
20 R10	se ha añadido un evento touched

Entity events are functions that are automatically invoked by ORDA each time entities and entity attributes are manipulated (added, deleted, or modified). You can write very simple events, and then make them more sophisticated.

No se puede activar directamente la ejecución de la función de evento. Events are called automatically by ORDA based on user actions or operations performed through code on entities and their attributes.

Nota de compatibilidad

ORDA entity events in the datastore are equivalent to triggers in the 4D database. However, actions triggered at the 4D database level using the 4D classic language commands or standard actions do not trigger ORDA events.

Generalidades

Nivel del evento

A entity event function is always defined in the Entity class.

It can be set at the entity level and/or the attribute level (it includes computed attributes). In the first case, it will be triggered for any attributes of the entity; on the other case, it will only be triggered for the targeted attribute.

For the same event, you can define different functions for different attributes.

You can also define the same event at both attribute and entity levels. The attribute event is called first and then the entity event.

Ejecución en configuraciones remotas

Normalmente, los eventos ORDA se ejecutan en el servidor.

In client/server configuration however, the touched() event function can be executed on the server or the client, depending on the use of local keyword. A specific implementation on the client side allows the triggering of the event on the client.

nota

ORDA constructor() functions are always executed on the client.

Con otras configuraciones remotas (p. ej. Qodly applications, REST API requests, or requests through Open datastore), the touched() event function is always executed server-side. It means that you have to make sure the server can "see" that an attribute has been touched to trigger the event (see below).

Tabla resumen

The following table lists ORDA entity events along with their rules.

Evento	Nivel	Nombre de la función	(C/S) Ejecutado en
Instanciación de entidades	Entity	constructor()	client
Atributo tocado	Atributo	event touched <attrName>()	Depende de la palabra clave local
	Entity	event touched()	Depende de la palabra clave local

nota

The constructor() function is not actually an event function but is always called when a new entity is instantiated.

Parámetro event

Event functions accept a single event object as parameter. When the function is called, the parameter is filled with several properties:

Nombre de propiedad	Disponibilidad	Tipo	Descripción
kind	siempre	String	Nombre del evento ("touched")
attributeName	Sólo para eventos que involucran un atributo	String	Nombre del atributo (por ejemplo, "nombre")
dataClassName	siempre	String	Nombre de la Dataclass (ej. "Company")

Event function description

Function event touched

Sintaxis

{local} Function event touched($event : Object)
{local} Function event touched <attributeName>($event : Object)
// code

This event is triggered each time a value is modified in the entity.

• if you defined the function at the entity level (first syntax), it is triggered for modifications on any attribute of the entity.
• if you defined the function at the attribute level (second syntax), it is triggered only for modifications on this attribute.

This event is triggered as soon as the 4D Server / 4D engine can detect a modification of attribute value which can be due to the following actions:

• en cliente/servidor con la palabra clave local o en 4D monousuario:
  • el usuario define un valor en un formulario 4D,
  • el código 4D realiza una asignación con el operador :=. El evento también se activa en caso de autoasignación ($entity.attribute:=$entity.attribute).
• in client/server without the local keyword: some 4D code that makes an assignment with the := operator is executed on the server.
• in client/server without the local keyword, in Qodly application and remote datastore: the entity is received on 4D Server while calling an ORDA function (on the entity or with the entity as parameter). It means that you might have to implement a refresh or preview function on the remote application that sends an ORDA request to the server and triggers the event.
• with the REST server: the value is received on the REST server with a REST request ($method=update)

The function receives an event object as parameter.

If this event throws an error, it will not stop the undergoing action.

nota

Este evento también se activa:

• cuando los atributos son asignados por el evento constructor(),
• when attributes are edited through the Data Explorer.

Ejemplo 1

You want to uppercase all text attributes of an entity when it is updated.

    //ProductsEntity class
Function event touched($event : Object)
	
	If (Value type(This[$event.attributeName])=Is text)
		This[$event.attributeName]:=Uppercase(This[$event.attributeName])
	End if 

Ejemplo 2

The "touched" event is useful when it is not possible to write indexed query code in Function query() for a computed attribute.

This is the case for example, when your query function has to compare the value of different attributes from the same entity with each other. You must use formulas in the returned ORDA query -- which triggers sequential queries.

To fully understand this case, let's examine the following two calculated attributes:

Function get onGoing() : Boolean
        return ((This.departureDate<=Current date) & (This.arrivalDate>=Current date))

Function get sameDay() : Boolean
        return (This.departureDate=This.arrivalDate)

Even though they are very similar, these functions cannot be associated with identical queries because they do not compare the same types of values. The first compares attributes to a given value, while the second compares attributes to each other.

• For the onGoing attribute, the query function is simple to write and uses indexed attributes:

Function query onGoing($event : Object) : Object
    var $operator : Text
    var $myQuery : Text
    var $onGoingValue : Boolean
    var $parameters : Collection
    $parameters:=New collection()

    $operator:=$event.operator
    Case of 
            : (($operator="=") | ($operator="==") | ($operator="==="))
                $onGoingValue:=Bool($event.value)
            : (($operator="!=") | ($operator="!=="))
                $onGoingValue:=Not(Bool($event.value))
            Else 
                return {query: ""; parameters: $parameters}
    End case 

    $myQuery:=($onGoingValue) ? "departureDate <= :1 AND arrivalDate >= :1" : "departureDate > :1 OR arrivalDate < :1"
        // the ORDA query string uses indexed attributes, it will be indexed
    $parameters.push(Current date)
    return {query: $myQuery; parameters: $parameters}

• For the sameDay attribute, the query function requires an ORDA query based on formulas and will be sequential:

Function query sameDay($event : Object) : Text
    var $operator : Text
    var $sameDayValue : Boolean

    $operator:=$event.operator
    Case of 
        : (($operator="=") | ($operator="==") | ($operator="==="))
            $sameDayValue:=Bool($event.value)
        : (($operator="!=") | ($operator="!=="))
            $sameDayValue:=Not(Bool($event.value))
        Else 
            return ""
        End case 

    return ($sameDayValue) ? "eval(This.departureDate = This.arrivalDate)" : "eval(This.departureDate != This.arrivalDate)"
        // the ORDA query string uses a formula, it will not be indexed

• Using a scalar sameDay attribute updated when other attributes are "touched" will save time:

    //BookingEntity class

Function event touched departureDate($event : Object) 

    This.sameDay:=(This.departureDate = This.arrivalDate) 
//
//
Function event touched arrivalDate($event : Object) 

    This.sameDay:=(This.departureDate = This.arrivalDate)

Ejemplo 3 (diagrama): cliente/servidor con la palabra clave local:

Ejemplo 4 (diagrama): cliente/servidor sin la palabra clave local

Ejemplo 5 (diagrama): Aplicación Qodly