复制 Groovy 类属性 [英] Copy Groovy class properties

问题描述

我想以通用方式将对象属性复制到另一个对象(如果目标对象上存在属性，我从源对象复制它).

I want to copy object properties to another object in a generic way (if a property exists on target object, I copy it from the source object).

我的代码使用 ExpandoMetaClass 可以正常工作，但我没有喜欢解决方案.有没有其他方法可以做到这一点?

My code works fine using ExpandoMetaClass, but I don't like the solution. Are there any other ways to do this?

class User {
    String name = 'Arturo'
    String city = 'Madrid'
    Integer age = 27
}

class AdminUser {
    String name
    String city
    Integer age
}

def copyProperties(source, target) {
    target.properties.each { key, value ->
        if (source.metaClass.hasProperty(source, key) && key != 'class' && key != 'metaClass') {
            target.setProperty(key, source.metaClass.getProperty(source, key))
        }
    }
}

def (user, adminUser) = [new User(), new AdminUser()]
assert adminUser.name == null
assert adminUser.city == null
assert adminUser.age == null

copyProperties(user, adminUser)
assert adminUser.name == 'Arturo'
assert adminUser.city == 'Madrid'
assert adminUser.age == 27

推荐答案

我认为您的解决方案非常好，并且走在正确的轨道上.至少我觉得很好理解.

I think your solution is quite good and is in the right track. At least I find it quite understandable.

该解决方案的更简洁版本可能是...

A more succint version of that solution could be...

def copyProperties(source, target) {
    source.properties.each { key, value ->
        if (target.hasProperty(key) && !(key in ['class', 'metaClass'])) 
            target[key] = value
    }
}

...但它并没有本质上的不同.我正在迭代源属性，以便我可以使用这些值分配给目标:).不过，它可能不如您的原始解决方案健壮，因为我认为如果目标对象定义了 getAt(String) 方法，它会中断.

... but it's not fundamentally different. I'm iterating over the source properties so I can then use the values to assign to the target :). It may be less robust than your original solution though, as I think it would break if the target object defines a getAt(String) method.

如果你想变得有趣，你可以这样做:

If you want to get fancy, you might do something like this:

def copyProperties(source, target) {
    def (sProps, tProps) = [source, target]*.properties*.keySet()
    def commonProps = sProps.intersect(tProps) - ['class', 'metaClass']
    commonProps.each { target[it] = source[it] }
}

基本上，它首先计算两个对象之间的共同属性，然后复制它们.它也有效，但我认为第一个更直接，更容易理解:)

Basically, it first computes the common properties between the two objects and then copies them. It also works, but I think the first one is more straightforward and easier to understand :)

有时少即是多.

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