com.github.gwtd3.api.functions

Interface KeyFunction<T>

public interface KeyFunction<T>

A function used to control how data is joined to elements.

Single argument Selection.data() methods use a default by-index behavior to map data with elements. This interface can be passed to Selection.data(com.google.gwt.core.client.JavaScriptObject, KeyFunction) and variants to map data to elements using a different criteria.

The #apply(Element, Datum, int) method will be called once for each element in the new data array, and once again for each existing element in the selection. The result will be used to map the passed data to the passed element.

Author:

Anthony Schiochet

See Also:

#apply(Element, Datum, int)

Method Summary

Methods

Modifier and Type	Method and Description
T	map(com.google.gwt.dom.client.Element context, Array<?> newDataArray, Value datum, int index) Invoked once for each datum in the new data array (A), then once for each element in the current selection (B).

Method Detail

map

T map(com.google.gwt.dom.client.Element context,
    Array<?> newDataArray,
    Value datum,
    int index)

Invoked once for each datum in the new data array (A), then once for each element in the current selection (B).

The returned value is used as a key to map the new data array elements to existing (or future) elements of the selection:

• when the value returned by A matches a return value of B, the new datum is associated to the corresponding element
• when the value returned by A does not match any return value of B, the new datum is associated to a placeholder for a new element ( the entering selection) and can be retrieved via UpdateSelection.enter()
• when the value returned by B does not match any return value of A, the element is put in the exiting selection and can be retrieved using UpdateSelection.exit().

Parameters:

context - the current element when this method is invoked for the existing elements of the selection, or null when this method is invoked for the new data array

newDataArray - the new data array when this method is invoked for the elements in the new data array, or null when this method is invoked for the existing elements of the selection.

datum - the datum element of the new data array, or the datum of the current element context

index - the index of the datum in the new data array, or the index of the element in the selection

Returns:

a key to be used to map new datum to existing elements.

See Also:

Selection.data(com.google.gwt.core.client.JavaScriptObject, KeyFunction)