grails - Groovy 中的闭包与委托(delegate)

Question

Closure u = {

if (params?.searchName) {
    def name = params?.searchName?.split(' ').toList()
    or {
        name.each {
            ilike('firstName', "%${it}%")
            ilike('lastName', "%${it}%")
        }
    }
}

def count = ShiroUser.createCriteria().get() {
    projections {
        count "id"
    }
    u.delegate = delegate
    u()
}

闭包 u 获取参数名称，然后代码拆分参数名称，然后使用 ilike 运算符进行检查，但是在获取 shiro 使用代码时执行此 u.delegate = delegate 然后调用 u() 闭包。请解释一下

为什么要这样做？

我们在哪个场景中执行此操作。

Answer 1

该代码有效地将闭包链接在一起:

def count = ShiroUser.createCriteria().get() {
  projections {
    count "id"
  }
  // Here you set the "context" of the 'u' closure to the current "context" of criteria query
  u.delegate = delegate 
  // here you run the 'u' closure and extend the criteria query with ilike search by name
  u()
}

另一个强调闭包委托(delegate)的例子是:

Closure u = { 
  // the closure from above
}

Closure counter = {
  projections {
    count "id"
  }
}

def count = ShiroUser.createCriteria().get() {
  counter.delegate = delegate
  counter.call() // same as counter()
  u.delegate = delegate
  u()
}

这样做的原因是 DRY。在这里，您可以将条件查询定义为闭包并重新使用它来获取结果和计数。