Groovy：運行期把方法mixin到對象實例

Groovy：運行期把方法mixin到對象實例

從Groovy 2.1 開始我們可以在運行期把方法mixin到對象實例。這個mixin和class的mixing用法很不一樣，他需要調用對象實例的metaClass屬性的mixin方法。

class Parrot {
    static String speak(String text) {
        /"$text" Polly wants a cracker!/
    }
}

// Runtime mixin on String object instead of class.
String s = 'Groovy is Gr8'
s.metaClass.mixin Parrot

assert s.speak() == '"Groovy is Gr8" Polly wants a cracker!'


String other = 'Groovy and Grails'
try {
    other.speak()
} catch (MissingMethodException e) {
    assert e.message.startsWith('No signature of method: java.lang.String.speak() is applicable for argument types: () values: []')
}