Groovy：生成equals和hashCode方法 [英] Groovy: generate equals and hashCode methods

问题描述

如果我有一个简单的Groovy类，例如

  class Address {
 
 Integer streetNumber 
字符串streetName 
字符串状态
字符串zip 
国家国家
} 
  

虽然我可以编写（或使用IDE来生成） hashCode 和等于方法：

  boolean equals（o）{
 if（this.is（o））return true; 
 
 if（！o || getClass（）！= o.class）return false; 
 
地址=（地址）o; 
 
 if（streetNumber？！streetNumber.equals（that.streetNumber）：that.streetNumber！= null）return false; 
 if（streetName？！streetName.equals（that.streetName）：that.streetName！= null）return false; 
 if（state？！state.equals（that.state）：that.state！= null）return false; 
 if（zip？！zip.equals（that.zip）：that.zip！= null）return false; 
 if（country？！zip.equals（that.zip）：that.zip！= null）return false; 
 
返回true; 
 
 
 int hashCode（）{
 int result =（streetNumber？streetNumber.hashCode（）：0）; 
 result = 31 * result +（streetName？streetName.hashCode（）：0）; 
 result = 31 * result +（state？state.hashCode（）：0）; 
 result = 31 * result +（zip？zip.hashCode（）：0）; 
 return 31 * result +（country？country.hashCode（）：0）; 
} 
  

尽管这样可以很好地工作，但我觉得我可以更好地使用Groovy的活力在少得多的代码中实现相同的目标。想到的一个方法是使用 .properties 来获取对象属性名称和值的映射。然后我可以迭代这些属性，在每个属性上调用 hashCode（）或 equals（）来获得相同的结果如上所述。

在我走下这条路之前，我只想检查其他人是否找到了解决这个问题的好办法。我对自己的解决方案有点小心，因为弄乱了 equals（）或 hashCode（）



谢谢，
Don

解决方案

我不是一个时髦的开发人员，但我从groovy 1.8了解到，您可以使用类型上的@EqualsAndHashCode调用AST转换。

If I have a simple Groovy class such as

class Address {

  Integer streetNumber
  String streetName
  String state
  String zip
  Country country    
}

Although I could write (or use an IDE to generate) hashCode and equals methods like:

boolean equals(o) {
    if (this.is(o)) return true;

    if (!o || getClass() != o.class) return false;

    Address that = (Address) o;

    if (streetNumber? !streetNumber.equals(that.streetNumber) : that.streetNumber!= null) return false;
    if (streetName? !streetName.equals(that.streetName) : that.streetName!= null) return false;
    if (state? !state.equals(that.state) : that.state!= null) return false;
    if (zip? !zip.equals(that.zip) : that.zip!= null) return false;
    if (country? !zip.equals(that.zip) : that.zip!= null) return false;

    return true;
}

int hashCode() {
    int result = (streetNumber ? streetNumber.hashCode() : 0);
    result = 31 * result + (streetName ? streetName.hashCode() : 0);
    result = 31 * result + (state ? state.hashCode() : 0);
    result = 31 * result + (zip ? zip.hashCode() : 0);
    return 31 * result + (country ? country.hashCode() : 0);
}

Although this will work fine, I feel I could be making better use of Groovy's dynamism to achieve the same thing in a lot less code. One approach that springs to mind is using .properties to get a map of an object's property names and values. I can then iterate over these properties, calling hashCode() or equals() on each one to achieve the same result as above.

Before I go down this path, I just want to check whether anyone else has found a good solution to this problem. I'm a bit wary of rolling my own solution, because the consequences of messing up equals() or hashCode() are potentially dire and hard to track down.

Thanks, Don

解决方案

I'm not a groovy developer, but I understood that from groovy 1.8 you can invoke the AST transformation using @EqualsAndHashCode on the type.

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