Event-Driven Programming

Event-driven programming in uniPaaS allows for the flow of the program execution to be triggered by events and handled in a desired manner. Event-based software development in uniPaaS is based on the very powerful uniPaaS engine.

The uniPaaS engine distinguishes the uniPaaS application platform from other approaches to application development and deployment. With pre-built capability to perform complex data manipulations that are transparent to the developer and end-user, the uniPaaS engine is key to the productivity and performance provide by Magic Software’s approach to application development and deployment.

The engine includes a set of operations for the developer’s use in creating applications. It also serves up a structure of execution steps called logic units, which work with the operations to perform tasks for the end-user. The developer doesn’t have to tell the uniPaaS application platform how-to do its job. The uniPaaS engine already knows how to perform such actions as opening files, reading records, sorting, displaying data on the screen, and more.

Contrast this with traditional 3GL and 4GL languages where the developer has to provide detailed instructions through program code to tell a program how-to implement each and every step, regardless of how tedious, repetitive they are. Programmers developing in Java and other languages get very frustrated by the fact that they have to repeat programming done hundreds if not thousands of times before by others. Many throw up their hands on the whole process of programming and say “Been there, done that” while others almost seem to enjoy being slaves to their code. By contrast, uniPaaS saves the developer considerable amounts of time by supplying these built-in operations and execution steps.

Naturally, the uniPaaS engine includes extensive support for event driven programming. Events, triggers and handlers are built in concepts. uniPaaS lets you define the uniPaaS logic as a response to implicit and explicit events that may occur during the execution of a task.

For the uniPaaS developer, an event is simply a logical definition of an occurrence. An event can be handled by an event handler to perform a flow of operations that the developer chooses. An event can also be assigned as a trigger of another user-defined event. When the triggering event is raised, it triggers the user-defined event. But uniPaaS isn’t just aware of events, it also allows the developer to handle events very specifically. In uniPaaS, a handler is a set of operations designated to be performed when a specified event is raised.

There are a number of different event types managed by uniPaaS.

System events are triggered by defined keystroke combinations. uniPaaS developers can define keystroke combinations for system events in a dialog box.

A uniPaaS internal event is usually handled by uniPaaS itself. But you can define a new or additional handler for these internal events.

Additional user events can be defined in the Event repository by the developer.

Timer Events within uniPaaS are based on durations, so that for every time interval of a specified duration, the event is invoked.

Expression Events are vents that are triggered when an expression evaluates to True. If the expression evaluates to false, then the event is not triggered.

Error Events are invoked when database-related errors occur such as a duplicate index or record that has been changed by another user.

ActiveX events are still used in some programs that use COM objects and Active X. An ActiveX event is raised for COM objects. If the event has built-in variables, they are created in the handler. It should be noted that ActiveX events are not supported with rich client tasks.

.NET events are preferred in rich client mode, where uniPaaS includes full support for .NET variables and events. When an event has built-in variables, they are created as parameters in the handler with the relevant .NET type. You can also define an event handler without defining a variable. In such a case, you can write the object from which you want to select the event.

uniPaaS events can be project-related events, triggered during the execution of any of the project's programs or task-related events confined to a specific task in which they are defined or to the task and its subtasks.

An event can have more than one trigger and more than one handler. Each trigger can raise the event in a different scenario. One or more handlers can handle the event for each scenario. This allows for complex event driven programming while avoiding the complexity of line-by-line coding. The uniPaaS application platform is available commercially from Magic Software Enterprises.