ORDA Events

Historia

Lanzamiento	Modificaciones
20 R10	Añadidos

ORDA 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.

You cannot directly trigger event function execution. Events are called automatically by ORDA based on user actions or operations performed through code on entities and their attributes.

Compatibility note

ORDA 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

Event level

A 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.

Execution in remote configurations

Usually, ORDA events are executed on the server.

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.

With other remote configurations (i.e. 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).

Summary table

The following table lists ORDA events along with their rules.

Evento	Nivel	Function name	(C/S) Executed on
Entity instantiation	Entity	constructor()	client
Attribute touched	Atributo	event touched <attrName>()	Depends on local keyword
	Entity	event touched()	Depends on local keyword

nota

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

event parameter

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	Event name ("touched")
attributeName	Only for events involving an attribute	String	Attribute name (e.g. "firstname")
dataClassName	siempre	String	Dataclass name (e.g. "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:

• in client/server with the local keyword or in 4D single-user:
  • the user sets a value on a 4D form,
  • the 4D code makes an assignment with the := operator. The event is also triggered in case of self-assignment ($entity.attribute:=$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)

nota

The function receives an event object as parameter.

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

nota

This event is also triggered:

• when attributes are assigned by the constructor() event,
• 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 with computed attributes, when you want to store a state depending on a comparison on the current value of underlying attributes. Por ejemplo:

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

This code can lead to time-consuming queries because the search is sequential due to the nature of the computed attribute. Using a non-computed 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)