Header predicates

A header predicate matches elements of a visualization, such as a measure header item or an attribute header item, with logic as simple or complex as you need. Drilling uses predicates to decide which parts of a visualization the user can drill into.

Structure

A header predicate (IHeaderPredicate) is a function that takes two arguments and returns a boolean:

type IHeaderPredicate = (header: IMappingHeader, context: IHeaderPredicateContext) => boolean;

• header (IMappingHeader) is an object that describes the item whose match is being tested: an attribute descriptor, an attribute result header, a measure descriptor, a total descriptor, or a color descriptor.

• context (IHeaderPredicateContext) is additional data that describes the context in which the match is being tested. Its dv property holds the DataViewFacade of the data view that produced the header passed as the first argument.

If the predicate returns true for an item, the item is matched.

The most common predicates are predefined in HeaderPredicates, exported from @gooddata/sdk-ui:

• identifierMatch(identifier, type?) matches an attribute or measure header by identifier, including measures derived from a master measure with that identifier. uriMatch(uri) does the same by URI, which only GoodData Legacy uses.
• localIdentifierMatch(localIdOrMeasure) matches a header by the local identifier of its attribute or measure.
• objRefMatch(objRef) and objMatch(obj) match a header by an ObjRef, or by an attribute or simple measure object from the generated catalog.
• attributeItemNameMatch(name) matches an attribute result header by its displayed value.
• composedFromIdentifier(identifier, type?) matches arithmetic measures that use a measure with that identifier as an operand. composedFromUri(uri) does the same by URI.

Example

You can also write your own predicates. This one matches all attribute values that start with a capital A:

import { type IHeaderPredicate } from "@gooddata/sdk-ui";
import { isResultAttributeHeader } from "@gooddata/sdk-model";

const startsWithA: IHeaderPredicate = (header) => {
    return isResultAttributeHeader(header) && !!header.attributeHeaderItem.name?.startsWith("A");
};

This one matches only attribute headers, and only when the visualization has at most three attributes:

import { type IHeaderPredicate } from "@gooddata/sdk-ui";
import { isAttributeDescriptor } from "@gooddata/sdk-model";

const attributesIfNoMoreThanThree: IHeaderPredicate = (header, context) => {
    if (context.dv.def().attributes().length > 3) {
        return false;
    }

    return isAttributeDescriptor(header);
};