如何从Groovy中的对象获取嵌套的属性值? [英] How to get nested property value from object in Groovy?

问题描述

考虑在Groovy中键入Company的情况:

Consider situation where in Groovy you have type Company:

class Company {
  def name
  def contactPerson
}

和contactPerson的Contact类型:

class Contact {
  def firstName
  def lastName
  def email
}

然后我们有Company类的实例:

Then we have instance of Company class:

def stackOverflow = new Company(
  name: "Stack Overflow",
  contactPerson: new Contact(
    firstName: "Joel",
    lastName: "Spolsky",
    email: "[e-mail]"
  )
)

在Groovy中，我们简单地拥有:

In Groovy we simple have:

assert stackOverflow.contactPerson.firstName == "Joel"

或:

assert stackOverflow['contactPerson']['firstName'] == "Joel"

还有:

assert stackOverflow.name == "Stack Overflow"

或:

assert stackOverflow['name'] == "Stack Overflow"

甚至:

def fieldName = 'name'
assert stackOverflow.${fieldName} == "Stack Overflow"

但是假设我们有:

def nestedFieldName = 'contactPerson.firstName'

是否有实现这种目标的Groovy方式:

Is there a Groovy-way to achieve something like this:

assert stackOverflow.${nestedFieldName} == "Joel"

?

推荐答案

一种方法是减少键序列:

One approach is to reduce a sequence of keys:

nestedFieldName.split('\\.')
    .inject(stackOverflow) { object, property -> 
        object[property]
     }

哪个返回'Joel'，可用于读取任意深度的值.

Which returns 'Joel', and could be used to read values at arbitrary depths.

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