Variables in QPR UI

Context variables in QPR UI is a mechanism for storing session time information and communicating between different user interface elements, such as views, panels and presentation objects. For example, the context can define the starting point for querying data from QPR ProcessAnalyzer or QPR Suite Web Service, or it can be used to define the chart type and colors.

Context Variable Behaviors

Each UI element (i.e. view, panel, presentation object) has an effective context, which consist of the current values of all context variables visible at that level, i.e. it's a combination of all upper level context variable values and the values defined in the level itself. Context variables can be defined in the following levels: Session, View, Panel and Presentation Object.

The context variables in QPR UI have the following types of behaviors which determine how the context variables work:

• Local: Defines a local context variable, which scope is the one where the variable is defined. When initialized, the local context variable gets a value that is set in its definition. Note that when setting a local context variable value, the value is changed for the nearest defined local context variable.
• Optional: Works like the local context variable, except the optional context variable gets its initial value from the upper level context. If the same name of context variable doesn't exist in the upper level during the initialization, the optional context variable will have the value that is set in its definition. After the optional context variable value is initialized, the changes in the upper level context doesn't affect the optional context variable value.
• Inherited: The context variable gets its value from the upper level if the same name of context variable exists in the upper level. If doesn't exist in the upper level, the context variable gets a value that is set in its definition. If the upper level value will be available after the initialization, the upper level value replaces the defined value.

Context variables in the session scope are not defined. They start to exist when they are set for the first time. That's why they don't have a behavior.

Context Variable Scopes

When setting context variable values via actions (for example in a data grid) or in HTML presentation object, you need to define a scope, which determines whether to change the session context variable or a local context variable (local or optional behavior). The available scopes are:

• Global: The context variable value will be set to the session context.
• Local: Default. The context variable value will be set on the nearest level where there is local or optional context variable defined. If the context variable is not defined on any level, the value will be set to the session context. Note that presentation object instances inside a repeater all have their own local scopes.

Context Variables Usage Example

There is a view with one panel, in which there is one presentation object. The Session context variable values are defined as follows:
800px

In the View Properties, the following context variable values are defined:
800px

In the Panel Properties, the following context variable values are defined:
800px

In the Presentation Object Properties, the following context variable values are defined:
800px

In the Effective View Context, these result into the values shown below. Note the Source column displaying the information where the effective context comes from: 800px

In the Effective Panel Context, these result into the values shown below. Note the Source column displaying the information where the effective context comes from: 800px

In the Effective Presentation Object Context, these result into the values shown below. Note the Source column displaying the information where the effective context comes from: 800px

To put it more concisely, the context variable values (and their behaviors) are as follows:

Context Variable	Session	View	Panel	Presentation Object
AccountManager	John Smith	William Taylor (Local)	Susan Chapman (Inherited)
Country	Sweden		Finland (Local)	China (Optional)
ProductGroup				Umbrellas (Local)
CustomerGroup		Kids

The effective context values are:

Context Variable	Session	View	Panel	Presentation Object
AccountManager	John Smith	William Taylor	William Taylor
Country	Sweden	Sweden	Finland	Finland
ProductGroup				Umbrellas
CustomerGroup		Kids	Kids	Kids

Context Variables and Web Browser History

Any time the session context is modified (like when clicking a Pushbutton or modifying ProcessAnalyzer Presentation Object settings that cause session variables to be modified), a browser history entry is created. The preceding values in the session context can be restored via the browser's Back button. Left-clicking the Back button will restore the previous session context values, whereas right-clicking the Back button will show a list of session context changes to select from. Selecting an entry on the list will restore the session context from that entry.

Defining View Properties and Variables

To define context variables, type in the name of the variable to the text field and click the check mark. After that, you can click the value field and type in the value for your context variable. Context variables starting with "sys:" are system variables which have special purpose in QPR UI - use them only for their intended purpose. The Behavior selection affects the context variable used explained in Context Variable Behaviors. To see what context variable values are used in the view, panel, or presentation object, select the Show effective context check box in the Context tab of the view, panel, or presentation object properties pages.

Variables Usage Example

There is a view with one panel, in which there is one presentation object. The Session variable values are defined as follows:

Variable name	Value
AccountManager	John Smith
Country	Sweden

In the View Properties, the following variable values are defined:

Variable name	Value	Behavior
AccountManager	William Taylor	Stored variable
CustomerGroup	Kids	Local variable

In the Panel Properties, the following variable values are defined:

Variable name	Value	Behavior
AccountManager	Susan Chapman	Local variable
Country	Finland	Local variable

In the Presentation Object Properties, the following variable values are defined:

Variable name	Value	Behavior
ProductGroup	Umbrellas	Stored variable

In the Effective View Context, these result into the values shown below. Note the Source column displaying the information where the effective context comes from:

Variable name	Value	Source	Scope
AccountManager	William Taylor	Scope of the view	View
Country	Sweden	Inherited from session context	Session
CustomerGroup	Kids	Scope of the view	View

In the Effective Panel Context, these result into the values shown below. Note the Source column displaying the information where the effective context comes from:

Variable name	Value	Source	Scope
AccountManager	Susan Chapman	Initialized from the panel's context	Panel
Country	Finland	Initialized from the panel's context	Panel
CustomerGroup	Kids	Inherited from the effective context of the view	View

In the Effective Presentation Object Context, these result into the values shown below. Note the Source column displaying the information where the effective context comes from:

Variable name	Value	Source	Scope
AccountManager	Susan Chapman	Inherited from the effective context of the panel	Panel
Country	Finland	Inherited from the effective context of the panel	Panel
ProductGroup	Umbrellas	Scope of the presentation object	Presentation object
CustomerGroup	Kids	Inherited from the effective context of the view	View

To put it more concisely, the context variable values (and their behaviors) are as follows:

Context Variable	Session	View	Panel	Presentation Object
AccountManager	John Smith	William Taylor (Stored variable)	Susan Chapman (Local variable)
Country	Sweden		Finland (Local variable)
ProductGroup				Umbrellas (Stored variable)
CustomerGroup		Kids (Local variable)

The effective context values are:

Context Variable	Session	View	Panel	Presentation Object
AccountManager	John Smith	William Taylor	Susan Chapman	Susan Chapman
Country	Sweden	Sweden	Finland	Finland
ProductGroup				Umbrellas
CustomerGroup		Kids	Kids	Kids

See Also

• Variable Tag in QPR UI
• QPR UI System Variables