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narkisr on 02/05/08

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Decorator Design Pattern Groovy

/ Published in: Groovy

Decorator design pattern implemented in Groovy, two implementation are provided, the first is naive and not general, the second is MOP based and can be used in much more scenarios.

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// the decorated class
package design.patterns.decorator
 
class Logger {
    def log(text) {
        println(text)
    }
}
 
// the naive implementation
package design.patterns.decorator
 
class LowerCaseLogger extends Logger {
 
    def logger
 
    LowerCaseLogger(log) {
        logger = log
    }
 
    def log(text) {
        logger.log(text.toLowerCase())
    }
 
 
    public static void main(String[] args) {
        def logger = new LowerCaseLogger(new Logger())
        logger.log('HELLO DECORATION')
    }
}
 
// the more general implementation
package design.patterns.decorator
 
class GenericLowerLogger {
    private delegate
 
    GenericLowerLogger(delegate) {
        this.delegate = delegate
    }
    def invokeMethod(String name, args) {
        def newargs = args.collect {arg ->
            if (arg instanceof String) return arg.toLowerCase()
            else return arg
        }
        delegate.invokeMethod(name, newargs)
    }
 
    public static void main(String[] args) {
        def logger = new GenericLowerLogger(new Logger())
        logger.log('HELLO DECORATION')// hello decoration
    }
}