Groovy Goodness: Use Constructor as Method Pointer

In Java 8 we can create a constructor reference. We must use the syntax Class::new and we get a constructor reference. This syntax is not supported in Groovy, but we can use the method pointer or reference syntax .& to turn a method into a closure. We can even turn a constructor into a closure and use it everywhere where closures are allowed.

In the following sample code we have a User class with some properties. Via the User.metaClass we can get a reference to the method invokeConstructor and turn it into a method closure:

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@groovy.transform.Immutable class User {     String name     int age }     // Initial list with user defined // using a map or Object array. def userList = [     // User defined as map, keys     // are properties of User class.     [name: 'mrhaki', age: 41],           // Object array with name and     // age properties for User class.     ['john', 30] as Object[] ]   // Create constructor reference. // Result is a closure we can use in our code. def createUser = User.metaClass.&invokeConstructor   // Invoke the collect method with our // constructor reference. At the end // all elements of the userList // are converted to new User objects. def users = userList.collect(createUser)     assert users.name == ['mrhaki', 'john'] assert users.age == [41, 30]

Code written with Groovy 2.4.1.