Applies to Pega Platform versions 7.2 through 8.3.1

Typical scenarios for designing nested grids

Errors

Limitations that interfere with nested grid behavior

Solutions

Typical scenarios for designing nested grids

As an application developer designing nested grids (grids inside of other grids) in Pega applications, you are apt to use the following approaches:

• Design a grid that contains cells and columns. In one of the columns, you design a section that includes another grid.
• Design a grid with rows that can be displayed in an expanded pane that contains another grid. Edits made to one row of the expanded pane are saved when the next row is selected for editing.
• Design a grid with rows that can be displayed in an embedded pane that contains another grid. Edits made to one row of the embedded pane are saved when the next row is selected for editing.

Errors

You might see an error on the screen or in the logs similar to the following examples:

Unable to determine value for <current>; reference is to a named page different from the starting context

com.pega.pegarules.pub.clipboard.InvalidParameterException . . .

Limitations that interfere with nested grid behavior

The design scenarios identified above work well, unless you encounter errors caused by the following limitations:

A paging-enabled grid inside a paging-enabled grid causes name conflict corruption

A nested grid’s styles are applied from the outer grid

A report definition grid in the second level of a nested grid causes errors and displays incorrect data

A flow action embedded in a grid does not work as expected in a collapsible section that contains another collapsible section

Inline nested grids with row editing using inline mode do not work and display in read-only mode

Refresh section runs the activity in the wrong context

Refresh when property changes does not work in the grid as expected

Clicking Add Item on Repeating Grid does not respond sometimes

A paging-enabled grid inside a paging-enabled grid causes name conflict corruption

This issue occurs only in cases where both the inner and outer grids are visible on load. Why? Because all paging-related parameters at the end of the grid layout are nullified in grid generation. Therefore, the generation of one grid corrupts the other grid’s parameters because the parameter names of both grids are the same.

Solution

• Maintain individual parameter pages for each grid.
• Maintain some index in the parameter name to uniquely identify each grid’s parameters.
• Scope the parameter page to the section level.

A nested grid’s styles are applied from the outer grid

When you include a Spreadsheet grid in the Expand Pane of a Transparent grid, then the inner grid, the Spreadsheet grid, inherits the styles of the outer grid, the Transparent grid. Why? Because the styles of the outer grid (the parent) always override the styles of the inner grid (the child).

Generating styles for all combinations of nested grids impedes performance. In addition to the inheritance of the parent grid styles by the child grid, the three grid styles are generated in order of precedence: Spreadsheet, Transparent, and Default.

Solution

Use the following code example when a grid with Spreadsheet style is inside a grid with Transparent style to apply the new style blocks as Spreadsheet:

- Div.Transparent Div.Spreadsheet .. {  Spreadsheet style blocks; } 

A report definition grid in the second level of a nested grid causes errors and displays incorrect data

In this scenario, an Expand Pane grid has a flow action that is bound to a report definition. The flow action refers to a grid that is bound to the report definition and the report definition accepts dynamic parameters. At run time, when the application user expands a row of the top-level grid, a top-level page is created with results of the inner report definition grid. When the user expands another row of the grid, the top-level page is replaced with the new results of the report definition. Because the inner grid is also of Expand Pane mode, expanding any row causes errors and sometimes shows incorrect data.

Solution

See Suggested local changes.

A flow action embedded in a grid does not work as expected in a collapsible section that contains another collapsible section

Your application has a section designed for Expand or Collapse All. Within that section is embedded another section designed for Expand or Collapse All. From the top embedded section, open a local flow action and Submit it. The bottom-level Expand or Collapse All section is hidden.

Solution

See Suggested local changes.

Inline nested grids with row editing using inline mode do not work and display in read-only mode

Your application has nested grids with inline mode row editing. On initial load, the section containing the nested grids is loaded as read-only. Notice that the nested grid section <div> displays the “readonly” attribute.

Solution

See Suggested local changes.

Refresh section runs the activity in the wrong context

Solution

See Suggested local changes.

 Refresh when property changes does not work in the grid as expected

Solution

See Suggested local changes.

Clicking Add Item on Repeating Grid does not respond sometimes

Steps to reproduce

1. Create a Repeating Grid with Master-Detail enabled for modal dialog (pop-up window) mode for editing the rows of the grid.
2. To the Detail window, add two layouts within the sections.
3. In the first layout, add a Dropdown control that updates and refers to pyWorkPage and the same Page that the Repeating Grid uses.
4. Design the second layout as a Repeating Grid layout, making the grid a nested grid, and include the buttons labeled Add and Delete for adding and deleting rows.
5. On the grid’s Master page, click Add to add an item in the Detail page pop-up window (the modal dialog box) and see how the Add action works as expected. On the added item, click Delete to delete it and see how the Delete action works as expected.
6. In the Detail page pop-up window, click Cancel to close the Detail page and return to the Master page.
7. On the Master page, click Add again to add an item in the Detail pop-up window, but notice that the Add button does not work.

Explanation

Repeating Grid with Master-Detail enabled for row editing does not work for actions in nested grids.

Solution

To prevent or resolve this problem, place the Dropdown control and the inner grid of the grid hierarchy in the same section.

Solutions

Debugging techniques

Suggested local changes

First, determine the root cause of the nested grid problem by trying the Debugging techniques.

Then try one of the Suggested local changes.

Debugging techniques

Try any one or all the following actions to determine the root cause of the nested grid problem.

Whenever a nested grid does not work as expected, take the following steps:

1. Check for the Errors that usually appear in run time.

2. Check to see if the nested grid design falls into one of the problem scenarios described in Limitations that interfere with nested grid behavior.

Suggested local changes

To overcome or avoid the Limitations that interfere with nested grid behavior, try the following local changes when developing your application:

• Replace a problematic nested grid (an inner grid) with a repeating dynamic layout.
• In a nested grid design where both the outer grid and the inner grid are paginated, take one of the following actions:
  • Disable pagination in one of the grids.
  • Move the grid to a dynamic layout and specify Defer Load for that grid.
• In a nested grid design where both the outer grid and the inner grid use Expand Pane mode, change either the inner grid or the outer grid to a modal dialog grid.

Related Content

How to add a Grid layout to a section

How to display row details in expanded panes in a repeating grid

Layouts