Groovy for Domain-specific Languages - Second Edition

Closure parameters

In our previous examples, we have made use of the it keyword. When a closure accepts only a single parameter, we are able to refer to this parameter as it and are free from having to explicitly define the parameter. The possible syntax definitions for a closure are:

• The default case allows any parameters to be passed to the closure:

  {
  // statements
  }

• The closure does not accept any parameters:

  { -> 
  // statements
  }

• The closure can accept one to many parameters with optional type annotations:

  { [type] param (,[type] param)* -> 
  // statements
  }

The parameter list is a comma-separated list of parameter names with optional type definitions. Closures behave slightly different depending on whether we supply the optional type:

given: "Closures ...