在调用groovy闭包之前检查是否没有传递任何参数

Question

i use maximumNumberOfParameters to check number of parameters used in closure ;

   def callerCls(Closure c){
     prinltn 'Nb :'+c.maximumNumberOfParameters;
      c();
  }

the pb that the follwing snippet has the same result .

  callerCls{


  }
 // and 
 callerCls{param1->

  }

Both of them return:

Nb :1

Although the follwing code, returns Nb :2 .

 callerCls{p1,p2->

      }

How to distinguish closure where no parameter used (as the first snippet) ?

Answer 1

Answer had been found in groovy official site

Parameter notes A Closure without -> , ie {} , is a Closure with one argument that is implicitly named as 'it'. (see below for details) In some cases, you need to construct a Closure with zero arguments, eg using GString for templating, defining EMC Property etc. You have to explicity define your Closure as { -> } instead of just { }

You can also use varargs as parameters, refer to the Formal Guide for details. A JavaScript-style dynamic args could be simulated, refer to the Informal Guide.