Collection_UniqueFunction (Geotools modules 31-SNAPSHOT API)

Object
- ExpressionAbstract
- - DefaultExpression
  - - FunctionExpressionImpl
    - - Collection_UniqueFunction

All Implemented Interfaces:

Expression, Function, FunctionExpression, Factory
```
public class Collection_UniqueFunction
extends FunctionExpressionImpl
```
Calculates the unique value of an attribute for a given FeatureCollection and Expression.

Since:

2.2M2

Author:

Cory Horner

Field Summary

Fields
Modifier and Type Field Description

static FunctionName NAME
- Fields inherited from class FunctionExpressionImpl
  fallback, functionName, name, params
- Fields inherited from interface Expression
  NIL

Constructor Summary

Constructors
Constructor Description

Collection_UniqueFunction()
Creates a new instance of Collection_UniqueFunction

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Object`	`evaluate(Object feature)`	Subclass should override, default implementation returns null.
`void`	`setExpression(Expression e)`
`void`	`setParameters(List<Expression> args)`	The provided arguments are evaulated with respect to the FeatureCollection.

Methods inherited from class FunctionExpressionImpl
accept, equals, functionName, getExpression, getFallbackValue, getFunctionName, getImplementationHints, getName, getParameters, hashCode, setFallbackValue, toString

Methods inherited from class DefaultExpression
isAttributeExpression, isExpression, isFunctionExpression, isGeometryExpression, isLiteralExpression, isMathExpression

Methods inherited from class ExpressionAbstract
evaluate

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

Methods inherited from interface Expression
evaluate

- Field Detail
  - NAME
```
public static FunctionName NAME
```
- Constructor Detail
  - Collection_UniqueFunction
```
public Collection_UniqueFunction()
```
    Creates a new instance of Collection_UniqueFunction
- Method Detail
  - setParameters
```
public void setParameters(List<Expression> args)
```
    The provided arguments are evaulated with respect to the FeatureCollection.
    For an aggregate function (like unique) please use the WFS mandated XPath syntax to refer to featureMember content.
    To refer to all 'X': featureMember/asterisk/X
    
    Specified by:
    
    setParameters in interface FunctionExpression
    
    Overrides:
    
    setParameters in class FunctionExpressionImpl
  - evaluate
```
public Object evaluate(Object feature)
```
    Description copied from class: ExpressionAbstract
    
    Subclass should override, default implementation returns null.
    
    Specified by:
    
    evaluate in interface Expression
    
    Overrides:
    
    evaluate in class FunctionExpressionImpl
    
    Returns:
    
    default implementation returns null
  - setExpression
```
public void setExpression(Expression e)
```