每个对象的Groovy动态属性 [英] Groovy dynamic property per object

问题描述

使用Groovy 1.8。我正在尝试创建一个动态类定义，它将缓存每个对象的属性。我没有使用 propertyMissing 而不添加对象的属性就好了。我只是想缓存属性会更有效率。

Using Groovy 1.8. I'm trying to create a dynamic class definition that will cache properties per object. I did use propertyMissing without adding the property to the object just fine. I just think caching the properties would be more efficient. Right?

请注意，每个实例都必须有自己的不同属性。

Note that each instance must have its own different properties.

以下代码正常工作： / p>

The code below works fine:

class C {}
def c = new C()
c.metaClass.prop = "a C property"
println c.prop

def x = new C()
x.prop

将输出：

a C property
groovy.lang.MissingPropertyException: No such property: prop for class: C

如果我需要这个问题：

class A {
    def propertyMissing(String name) {
        if(!this.hasProperty(name)) {
            println "create new propery $name"
            this.metaClass."$name" = "Dyna prop $name"
            println "created new propery $name"
        }
        this.metaClass."$name"
    }
}

a = new A()
println a.p1

对于 A ，我得到crea新的属性，但行 this.metaClass。$ name=Dyna prop $ name失败与：没有这样的属性：p1对于第5行的课程

For A, I get as far as "create new property", but the line this.metaClass."$name" = "Dyna prop $name" fails with: No such property: p1 for class at line 5

有什么问题？

推荐答案

此代码应该做你想要的：

This code should do what you want:

class A {
  A() {
    def mc = new ExpandoMetaClass( A, false, true)
    mc.initialize()
    this.metaClass = mc
  }

  def propertyMissing( String name ) {
    println "create new propery $name"
    def result = "Dyna prop $name"
    this.metaClass."$name" = result
    println "created new propery $name"
    result
  }
}

a = new A()
println a.p1
println a.p1

输出：

create new propery p1
created new propery p1
Dyna prop p1
Dyna prop p1

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