[英]Grails/Groovy: Understanding the parameters of the closure code
I'm new to Grails/Groovy, and so please bear with me as I try to understand a piece of code that I had come across in a book. 我是Grails / Groovy的新手,所以在尝试理解我在书中遇到的一段代码时,请多多包涵。
It is a simple Album domain class: 这是一个简单的Album域类:
class Album {
String artist
String title
List songs = []
List durations = []
static constraints = {
artist blank: false
title blank: false
songs minSize:1, validator:{ val, obj ->
if(val.size() != obj.durations.size())
return "songs.durations.not.equal.size"
}
}
My question comes from the constraints property block of code. 我的问题来自代码的constraints属性块。
In the validator constraint, the author uses a closure. 在验证者约束中,作者使用闭包。
But what exactly are "val" and "obj"? 但是“ val”和“ obj”到底是什么? What values will they be given?
他们会得到什么价值?
Also, a bonus question, what type is "constraints"? 另外,还有一个奖励问题,“约束”是什么类型? I don't think it is a map as they are defined as [ ] in Groovy.
我不认为这是一张地图,因为它们在Groovy中被定义为[]。 Coming from a Java perspective,
x = { .. }
is an array, but I'm not sure it is the same in Groovy. 从Java的角度来看,
x = { .. }
是一个数组,但是我不确定Groovy中的数组是否相同。
Thanks for the help! 谢谢您的帮助!
Your first question, val
and obj
parameters refer to the value of the property and a pointer to the instance, respectively. 第一个问题,
val
和obj
参数分别引用属性的值和实例的指针。 The documentation for custom validation routines explains this in further detail. 自定义验证例程的文档对此进行了更详细的说明。
As for the bonus question constraints
is a Groovy closure . 至于奖金问题的
constraints
是Groovy 闭包 。
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