Variables in QPR UI
Context variables in QPR UI is a mechanism for storing and communicating configuration and settings data between the 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 chart colors.
Effective Context and Context Inheritance
Effective context of a single UI element level consist of the current values of all context variables at that level. The effective context is a combination of all upper level values and the values defined in the current level.
The context variables in QPR UI have three types of behavior: Inherited, Local, and Optional. There are the following levels where the context variables are defined: Session, View, Panel and Presentation Object levels. The context variable behavior type defines how the context variable value is inherited from the Session context, i.e. what the effective contexts of the view, its panel(s), and presentation object(s) are:
- Inherited: Context variables will inherit the context variable value from an upper level in the context inherirance hierarchy, if there is an effective context variable value on the upper level. If there isn't an effective context variable value on the higher level, the defined value defined for the variable will be used.
- Local: Value of the context variable will overwrite any existing effective value of the same context variable, and setting the value on a higher level will not change the value of the context variable on the level where the behavior is defined as "Local".
- Optional: Context variables will inherit the context variable value from an upper level in the context inherirance hierarchy, if there is an effective context variable value on the upper level. If there isn't an effective context variable value on the higher level, the defined value defined for the variable will be used. After the optional context variable value is calculated once (i.e. the view is opened), the value isn't changed even after the value is changed on an upper level, nor does changing the value of the context variable with "Optional" behavior have any effect on the upper level value.
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 Variable Scope
When setting context variable values via actions (for example in a data grid), you can define a scope for the context variable. The scope defines the level (presentation object, panel, view, or session) where the context variable value will be set. 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 the variable behavior has been defined as "Local". 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.
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 |