Difference between revisions of "Variables in QPR UI"

Revision as of 13:30, 14 August 2018

Context variables in QPR UI are for storing session time information and communicating between different user interface elements, such as views, panels and presentation objects.

Context Variable Behaviors

Variables can be defined for views, panels and presentation objects (called UI elements) which form a scope for the defined variables. Variables are visible and accessible in the scope where they have been defined and also in all sub scopes in the hierarchy of UI elements. For example, a variable defined in a view scope is visible in all panels and presentation objects in the view. Also a variable defined in a panel is visible in all presentation objects in the panel, but not in presentation objects in other panels. In addition to UI elements (view, panel and presentation object), variables can exist in session scope. The session scope is visible in all views, i.e. session variables are preserved when opening another view. Thus the visibility hierarchy for variables is (starting from the top):

Session
View
Panel
Presentation object

When setting or getting variable values and two variables with same names exist in different scopes, the variable in the lower scope takes priority over the variable in the upper scope, i.e. the lower scope variable hides the upper scope variable within the scope of the lower scope variable.

Each defined variable have a behavior which determine how the variables work when setting and getting their values. The following behaviors are available:

Variable behavior	Description
Local	Local variables are visible in the scope where the variable is defined and also in all its sub scopes. When initialized, the local variable gets a value that is set in its definition (in the Context tab). When a local variable value is changed by logic in a presentation object (e.g. data grid action), the change is made to the variable in the nearest scope of the presentation object in the UI element hierarchy where the variable has been defined as Local.
Optional	Optional variables work like the local variables, except the optional variables get their initial values from the upper scope when the variables are initialized. For example, optional variables in view scope get their values from the session scope when a view is opened, and optional variables in the panel scope get their values from the view scope when the panel is initialized. If a variable having the same name doesn't exist in any of the upper scope, the optional variable will have the value that is set in its definition (in the Context tab). After the optional variable value is initialized, any changes in the upper scope variables don't affect the optional variable value.
Stored variable	Stored variables work like Local variables, except that when the view is saved, the current value of the Stored variable is saved to the view at the level where the Stored variable is defined.
Inherited	Unlike local and optional variables, inherited variables are not independent variables but they are just default values for non-existing variables. Thus, if a variable with the same name exist in the upper scope, the defined inherited variable doesn't have any effect. Only if no upper scope variable exist, the value defined for the inherited variable (in the Context tab) is used in the inherited variables' scope when referring to a variable with that name. Inherited variable values cannot be set by presentation objects, so when trying to set an inherited variable value, the value is set to the session scope variable.

Note that variables in the session scope cannot be defined like the UI element variables, but session scope variables are created when they are set for the first time during a user session.

When presentation objects set variable values, either the nearest UI element scope variable or the session scope variable can be set. In a data grid actions the setting is called scope with alternatives local and global, and in HTML presentation object functions, it's done using a parameter named presentation object runtime id. When setting a UI element variable, always the nearest variable value in the hierarchy is set. For example, when setting a value from a data grid, the data grid presentation object is the nearest scope, the panel is the next and the view scope is after the panel. If there is no variable in any UI element scope defined, the value is set to the session scope.

When creating bookmarks, currently only the session scope variables are stored to the bookmark.

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:

Variable name	Value
AccountManager	John Smith
Country	Sweden

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

Variable name	Value	Behavior
AccountManager	William Taylor	Stored
CustomerGroup	Kids	Local

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

Variable name	Value	Behavior
AccountManager	Susan Chapman	Local
Country	Finland	Local

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

Variable name	Value	Behavior
ProductGroup	Umbrellas	Stored

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)	Susan Chapman (Local)
Country	Sweden		Finland (Local)
ProductGroup				Umbrellas (Stored)
CustomerGroup		Kids (Local)

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

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.

Setting Context Variable Values in URL

It's possible to set context variable values in the URL of the QPR UI view. To do this, append "&<variable name>=<variable value>" to the end of the URL. For example: http://localhost:8080/ui/#/dashboard?sys:dashboard=24026&myvariable=myvalue

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