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/*
* Copyright 2000-2021 Vaadin Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.vaadin.data;
import com.vaadin.server.SerializableFunction;
/**
* A callback interface for providing values from a given source.
* <p>
* For example this interface can be implemented to simply extract a value with
* a getter, or to create a composite value based on the fields of the source
* object.
*
* @author Vaadin Ltd.
* @since 8.0
*
* @param <SOURCE>
* the type of the object used to provide the value
* @param <TARGET>
* the type of the provided value
*/
@FunctionalInterface
public interface ValueProvider<SOURCE, TARGET>
extends SerializableFunction<SOURCE, TARGET> {
/**
* Returns a value provider that always returns its input argument.
*
* @param <T>
* the type of the input and output objects to the function
* @return a function that always returns its input argument
*/
public static <T> ValueProvider<T, T> identity() {
return t -> t;
}
/**
* Provides a value from the given source object.
*
* @param source
* the source to retrieve the value from
* @return the value provided by the source
*/
@Override
public TARGET apply(SOURCE source);
}
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