Groovy 全局闭包在嵌套方法调用中不起作用

Question

我有一个简单的闭包，我希望能够在我的代码中使用它来测量任何其他闭包所需的时间。它看起来像这样:

def benchmark = {name,closure ->
    start = System.currentTimeMillis()
    ret =  closure.call()
    now = System.currentTimeMillis()   println(name + " took: " +  (now - start))
    ret
}

当从同一范围调用时它会起作用，如下所示:

benchmark('works') { println("Hello, World\n")}

但是当它调用嵌套作用域时它似乎不起作用

def nested()
{
   benchmark('doesnt_work'){print("hello")}
}

nested()

Answer 1

那是因为您在脚本中运行它。

Groovy 将以上内容转换为:

class Script {
    def run() {
        def benchmark = {name,closure -> ...
        nested()
    }

    def nested() {
        benchmark('doesnt_work'){print("hello")}
    }
}

如您所见，闭包对于隐式 run 方法是本地的，但 nested 方法属于该类...

我相信你有3个选择:

1. 将nested设为闭包，它们将存在于同一范围内

   def benchmark = {name,closure ->
       start = System.currentTimeMillis()
       ret =  closure.call()
       now = System.currentTimeMillis()
       println(name + " took: " +  (now - start))
       ret
   }
   
   def nested = {
      benchmark('doesnt_work'){print("hello")}
   }
   
   nested()
   

2. 编写适当的类并自己控制范围

   class Test {
       def benchmark = {name,closure ->
           long start = System.currentTimeMillis()
           def ret =  closure.call()
           long now = System.currentTimeMillis()
           println(name + " took: " +  (now - start))
           ret
       }
   
       def nested() {
           benchmark('doesnt_work'){print("hello")}
       }
   
       static main( args ) {
           new Test().nested()
       }
   }
   

3. 在 def benchmark = {name,closure -> ... 之前添加 @groovy.transform.Field 这会将闭包定义提升为property of this Script class

   @groovy.transform.Field def benchmark = { name, closure ->
       start = System.currentTimeMillis()
       ret =  closure.call()
       now = System.currentTimeMillis()
       println(name + " took: " +  (now - start))
       ret
   }
   
   def nested() {
      benchmark('doesnt_work'){print("hello")}
   }
   
   nested()