$construct and $initialize

Doing anything in the $construct methods of windows tends to push the stack limit especially when we have a container window that has multiple subwindows which are also running code in their $construct methods.

The other problem with $construct methods is that they are called by Omnis Studio so if an error happens in a $construct method we have no way of communicating the error to StudioWorks and stopping method excecution. Error handling and reporting them to the user from $construct methods gets messy.

In swGui5 we avoid using the $construct method in any class. With window instances it frees us from having to make sure the pWinInstID parameter is sent to a window's $construct.

In swGui5 instantiating a window triggers very little code. After the window has been instantiated we send a $initialize message to the window instance with the appropriate parameters. Normally the $initialize message tells the window instance its wininstid, mode, and datalist. Based on the wininstid the window can find out other properties like toolbar buttons, searchbarvisible, etc. and add them if required.

The downside on doing very little in the $construct is that a window can become visible to the user before it is ready. The solution is simple. In StudioWorks all windows are instantiated as subwindows, so we simply need to hide the subwindow field until after it has been initialized.

MVC Model-View-Controller

The following is a definition of MVC in Wikepedia.

WCO Window Controller Objects

The original release of StudioWorks used window controller objects (WCOs) as the controller in the MVC architecture.

1. Model - Table class with check data object classes
2. View - Window class, Remote form, Ultrathin web page
3. Controller - Window Controller object class

The Window Controller Objects were dropped from StudioWorks in version 3. Window Controller Objects were dropped because object instances were unstable in earlier versions of Omnis Studio and they had to be instantiated by the window class instance.

Omnis Studio version 3 introduced the object reference datatype which made it possible to instantiate an object to its own spot in memory and pass stable references to the object. The object reference datatype makes it possible for StudioWorks to reintroduce Window Controller Objects.

oWindows_wco

In swGui5 as with swGui4 requests to open a new window are sent to an oWindow object class. The difference in swGui5 is that rather than directly opening a window class, oWindow_window controller object opens an owcWinInstID window controller object reference instance for the specified WinInstID. An object reference to the object instance is stored in an iWCOsList inside oWindow_window controller object.

oWindow_window controller object then sends the Window Controller Object instance an $initialize message which allows it to define and build any lists and get any addition information it needs prior to opening a window. oWindow_window controller object then sends an $openWindow message to the Window Controller Object. The Window Controller Object opens a window instance and attaches itself as the Window Controller Object to the window instance.

All window events and are passed from the window to the attached Window Controller Object. This gives the developer the flexibility of deciding which window controller to connect to a window instance.

Responsibilities - Window

The window instance is responsible for:

1. Setting text for field labels, tooltips, buttons, and menus.
2. Field handling and decoration, including lookup field handling and setting foreign keys.
3. Turning scrollbars on/off.
4. Adding toolbar buttons, menus, and searchbar, based on window instances meta-data.

Responsibilities - Remote Form

The remote form is generated by a remote form generator object in StudioWorks.

The remote form generator is responsible to prepare a remote form with:

1. Text for field labels, tooltips, buttons, and menus.
2. Adding toolbar buttons, menus, and searchbar, based on window instances meta-data.

The remote form instance is responsible for:

1. Field handling and decoration, including lookup field handling and setting foreign keys.
2. Turning scrollbars on/off.

Responsibilities - Ultrathin HTML

The ultrathin web page is generated by an HTML generator object in StudioWorks.

The HTML generator is responsible to return HTML for:

1. Text for field labels, tooltips, buttons, and menus.
2. Adding toolbar buttons, menus, and searchbar, based on window instances meta-data.

Javascript files on the server are responsible for:

1. Field handling and decoration, including lookup field handling and setting foreign keys.

The web browser is responsible for:

1. Turning scrollbars on/off.

StudioWorks Documentation - Copyright 2005 Vencor Software