    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}