IterativeCondition (Flink : Libraries : CEP 2.1.0 API)

java.lang.Object
- org.apache.flink.cep.pattern.conditions.IterativeCondition<T>

All Implemented Interfaces:

Serializable, org.apache.flink.api.common.functions.Function

Direct Known Subclasses:

RichIterativeCondition, SimpleCondition
```
@PublicEvolving
public abstract class IterativeCondition<T>
extends Object
implements org.apache.flink.api.common.functions.Function, Serializable
```
A user-defined condition that decides if an element should be accepted in the pattern or not. Accepting an element also signals a state transition for the corresponding NFA.
A condition can be a simple filter or a more complex condition that iterates over the previously accepted elements in the pattern and decides to accept a new element or not based on some statistic over these elements. In the former case, the condition should extend the SimpleCondition class. In the later, the condition should extend this class, which gives you also access to the previously accepted elements through a IterativeCondition.Context.
An iterative condition that accepts an element if i) its name is middle, and ii) the sum of the prices of all accepted elements is less than 5 would look like:
```
{@code
 private class MyCondition extends IterativeCondition {
```
See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static interface IterativeCondition.Context<T>
The context used when evaluating the condition.

Constructor Summary

Constructors
Constructor Description

IterativeCondition()

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`abstract boolean`	`filter(T value, IterativeCondition.Context<T> ctx)`	The filter function that evaluates the predicate.

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

- Constructor Detail
  - IterativeCondition
```
public IterativeCondition()
```
- Method Detail
  - filter
```
public abstract boolean filter(T value,
                               IterativeCondition.Context<T> ctx)
                        throws Exception
```
    The filter function that evaluates the predicate.
    IMPORTANT: The system assumes that the function does not modify the elements on which the predicate is applied. Violating this assumption can lead to incorrect results.
    
    Parameters:
    
    value - The value to be tested.
    
    ctx - The IterativeCondition.Context used for the evaluation of the function and provides access to the already accepted events in the pattern (see IterativeCondition.Context.getEventsForPattern(String)).
    
    Returns:
    
    true for values that should be retained, false for values to be filtered out.
    
    Throws:
    
    Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.