在groovy中动态添加一个属性或方法给一个对象

#在groovy中动态添加一个属性或方法给一个对象| 来源: 网络整理| 查看: 265

百度翻译此文有道翻译此文问题描述

Is it possible to add a property or a method to an object dynamically in Groovy? This is what I have tried so far:

class Greet { def name Greet(who) { name = who[0].toUpperCase() + [1..-1] } def salute() { println "Hello $name!" } } g = new Greet('world') // create object g.salute() // Output "Hello World!" g.bye = { println "Goodbye, $name" } g.bye()

But I get the following exception:

Hello World! Caught: groovy.lang.MissingPropertyException: No such property: bye for class: Greet Possible solutions: name at test.run(greet.groovy:11) 推荐答案

If you just want to add the bye() method to the single instance g of the class Greet, you need to do:

g.metaClass.bye = { println "Goodbye, $name" } g.bye()

Otherwise, to add bye() to all instance of Greet (from now on), call

GreetaClass.bye = { println "Goodbye, $name" }

But you'd need to do this before you create an instance of the Greet class

Here is a page on the per-instance metaClass

And here is the page on MetaClasses in general

Also, there's a bug in your constructor. You're missing who from infront of your [1..-1] and if the constructor is passed a String of less than 2 characters in length, it will throw an exception

A better version might be:

Greet( String who ) { name = who.inject( '' ) { String s, String c -> s += s ? c.toLowerCase() : c.toUpperCase() } }

As metioned in the comments,

Greet( String who ) { name = who.capitalize() }

is the proper way

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