    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
    015    package 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     */
    025    public interface ComputedValue<T>
    026    {
    027        /**
    028         * Computes or otherwise provides the value, given the instance's context.
    029         */
    030        T get(InstanceContext context);
    031    }