Learning > presentation > hierarchies > GroupingRule
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Grouping Customization Rule

Grouping rules provide advanced ways to group instances when creating hierarchies.

It allows to define these types of groupings:

  • Group by base class.
  • Group by any property of the instance by a common value or a range of values.
  • Group multiple instances with the same label in to one ECInstance node. This can be used in cases when these instances represent the same object for the user.

The rule works in conjunction with other grouping options available in navigation specifications: groupByClass and groupByLabel. The grouping hierarchy looks like this:

The rule itself works in a similar way as hierarchy rules - rule identifies what to group and it has specifications which tell how to do that.

Attributes

Name Required? Type Default Meaning
Filtering
priority No number 1000 Defines the order in which presentation rules are evaluated.
onlyIfNotHandled No boolean false Should this rule be ignored if there is already an existing rule with a higher priority.
condition No ECExpression "" Defines a condition for the rule, which needs to be met in order to execute it.
class Yes SingleSchemaClassSpecification Specification of ECClass which should be grouped using this rule.
Grouping
groups Yes GroupingSpecification[] Specifications of grouping which should be applied to matching ECInstances.

Grouping Specifications

There are 3 types of supported grouping: base class grouping, property grouping and same label instance grouping.

Base Class Grouping

Base class grouping allows grouping ECInstance nodes by their base class.

Attributes

Name Required? Type Default Meaning
createGroupForSingleItem No boolean false Should the grouping node be created if there is only one item in that group.
baseClass No SingleSchemaClassSpecification Rule's class Specification of the base ECClass to group by.

Property Grouping

Property grouping allows grouping by property of the instance by a value or by ranges of values.

Attributes

Name Required? Type Default Meaning
createGroupForSingleItem No boolean false Should the grouping node be created if there is only one item in that group.
createGroupForUnspecifiedValues No boolean true Should a separate grouping node be created for nodes whose grouping value is not set.
propertyName Yes string Name of the ECProperty which is used for grouping.
imageId No string "" ID of an image to use for the grouping node.
groupingValue No `"PropertyValue" "DisplayLabel"` "DisplayLabel" Should the instances be grouped on display label or the grouping property value. Note: Grouping by property value is required if the display label is overridden to display grouped instances count. Warning: Grouping by label and sorting by property value is not possible.
sortingValue No `"PropertyValue" "DisplayLabel"` "DisplayLabel" Should the nodes be sorted by display label or the grouping property value. In most cases the result is the same, unless [[LabelOverride]] rule is used to change the display label. Note: Sorting by property value only makes sense when instances are grouped by property value as well. Warning: Grouping by label and sorting by property value is not possible.
ranges No PropertyRangeGroupSpecification[] [] Ranges into which the grouping values are divided. Instances are grouped by value if no ranges are specified.

PropertyRangeGroupSpecification Attributes

Name Required? Type Default Meaning
imageId No string imageId of the property group specification ID of an image to use for the grouping node.
label No string "{from value} - {to value}" Grouping node label. May be localized.
fromValue Yes string Value that defines the range start (inclusive)
toValue Yes string Value that defines the range end (inclusive)

Same Label Instance Grouping

Allows grouping multiple instances with the same label into one ECInstance node. Similar to display label grouping, but instead of showing a grouping node with multiple grouped nodes, it shows a single ECInstances node which represents multiple ECInstances.

Attributes

Name Required? Type Default Meaning
applicationStage No SameLabelInstanceGroupApplicationStage "Query" Stage of hierarchy creation at which the rule is applied.

Example

{
  "ruleType": "Grouping",
  "priority": 999,
  "class": { "schemaName": "MySchema", "className": "MyClass" },
  "groups": [{
    "specType": "Property",
    "propertyName": "MyProperty",
    "imageId": "MyImage",
    "createGroupForSingleItem": true,
    "createGroupForUnspecifiedValues": false
  }]
}

Last Updated: 08 January, 2020