DefFunction (Lucene 8.1.0 API)

java.lang.Object
- org.apache.lucene.queries.function.ValueSource
- - org.apache.lucene.queries.function.valuesource.MultiFunction
  - - org.apache.lucene.queries.function.valuesource.DefFunction

```
public class DefFunction
extends MultiFunction
```
ValueSource implementation which only returns the values from the provided ValueSources which are available for a particular docId. Consequently, when combined with a ConstValueSource, this function serves as a way to return a default value when the values for a field are unavailable.

Nested Class Summary
- Nested classes/interfaces inherited from class org.apache.lucene.queries.function.valuesource.MultiFunction
  MultiFunction.Values

Field Summary
- Fields inherited from class org.apache.lucene.queries.function.valuesource.MultiFunction
  sources

Constructor Summary

Constructors
Constructor Description

DefFunction(List<ValueSource> sources)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`FunctionValues`	`getValues(Map fcontext, LeafReaderContext readerContext)`	Gets the values for this reader and the context that was previously passed to createWeight().
`protected String`	`name()`

Methods inherited from class org.apache.lucene.queries.function.valuesource.MultiFunction
allExists, allExists, anyExists, anyExists, createWeight, description, description, equals, hashCode, toString, valsArr

Methods inherited from class org.apache.lucene.queries.function.ValueSource
asDoubleValuesSource, asLongValuesSource, fromDoubleValuesSource, getSortField, newContext, toString

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - DefFunction
```
public DefFunction(List<ValueSource> sources)
```
- Method Detail
  - name
```
protected String name()
```
    Specified by:
    
    name in class MultiFunction
  - getValues
```
public FunctionValues getValues(Map fcontext,
                                LeafReaderContext readerContext)
                         throws IOException
```
    Description copied from class: ValueSource
    
    Gets the values for this reader and the context that was previously passed to createWeight(). The values must be consumed in a forward docID manner, and you must call this method again to iterate through the values again.
    
    Specified by:
    
    getValues in class ValueSource
    
    Throws:
    
    IOException