Create Predicates

Predicates allow you to create a match between elements (for example, a measure header item or an attribute header item) with an arbitrary level of complexity.

For example, a predicate that creates a simple match based on an equation may look like the following:

(headerItem) => headerItem.measureHeaderItem.localIdentifier === 'm1_localIdentifier'

Here is an example of a predicate that increments the callCounter variable in the predicate's closure every time the predicate is called and returns true if callCounter is an even number:

let callCounter = 0;

const predicate = () => (callCounter++ % 2) === 0

A predicate is called with the following parameters:

• Execution header with the type as defined here

• Context with the type defined here

  Context is an object that contains the afm and executionResponse keys. These keys can be used for building complex matching conditions.

For more advanced predicates, see the predicate factories in HeaderPredicateFactory.