001// Copyright 2011 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.plastic;
016
017/**
018 * Provides an indirect, or computed, value. This is used for certain
019 * kinds of injection, where the exact value to be injected must be computed
020 * for each <em>instance</em> being instantiated, rather than for the
021 * class as a whole.
022 * 
023 * @see PlasticField#injectComputed(ComputedValue)
024 */
025public interface ComputedValue<T>
026{
027    /**
028     * Computes or otherwise provides the value, given the instance's context.
029     */
030    T get(InstanceContext context);
031}