Copyright 2014 Netflix, Inc.
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.
/**
 * Copyright 2014 Netflix, Inc.
 *
 * 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.netflix.config;

import com.google.common.base.Function;

A property wrapper that can be used to derive any type of data as property value 
from string format.
Author:
awang
Type parameters:
<T> – Type of the property value/**
 * A property wrapper that can be used to derive any type of data as property value 
 * from string format.
 * 
 * @author awang
 *
 * @param <T> Type of the property value
 */
public class StringDerivedProperty<T> extends PropertyWrapper<T> {
    protected final Function<String, T> decoder;
    
    private volatile T derivedValue;
    
    
Create an instance of the property wrapper.
 
Params:
decoder – the function used to parse the string format into the desired data type./**
     * Create an instance of the property wrapper.
     *  
     * @param decoder the function used to parse the string format into the desired data type.
     */
    public StringDerivedProperty(String propName, T defaultValue, Function<String, T> decoder) {
        super(propName, defaultValue);
        this.decoder = decoder;
        propertyChangedInternal();
    }

    private final void propertyChangedInternal() {
        String stringValue = prop.getString();
        if (stringValue == null) {
            derivedValue = defaultValue;
        } else {
            derivedValue = decoder.apply(stringValue);
        }        
    }
    
    @Override
    protected final void propertyChanged() {
        propertyChangedInternal();
        propertyChanged(getValue());
    }
    
    @Override
    public T getValue() {
        return derivedValue;
    }
}