groovy.lang

Annotation Type Newify

@Documented
 @Retention(value=SOURCE)
 @Target(value={CONSTRUCTOR,METHOD,TYPE,FIELD,LOCAL_VARIABLE})
public @interface Newify

Annotation that supports writing constructor call expressions without the 'new' keyword. Instead they can be written "Ruby-style" as a method call to a 'new' method or "Python-style" by just omitting the 'new' keyword.

WARNING: For the Python style with class-name-matching pattern, the pattern should be chosen as to avoid matching method names if possible. If following Java/Groovy naming conventions, class names (contrary to method names) start with an uppercase letter. In this case pattern="[A-Z].*" (see Pattern for supported Java pattern syntax) is the recommended pattern to allow all classes to be created without requiring a new keyword. Using a pattern that also matches method names (e.g. ".+", ".*" or "[a-zA-Z].*") might negatively impact build performance, since the Groovy compiler will have to match every class in context against any potential constructor call.

@Newify allows you to write code snippets like this ("Python-style"):

  @Newify([Tree,Leaf]) class MyTreeProcessor {
     def myTree = Tree(Tree(Leaf("A"), Leaf("B")), Leaf("C"))
     def process() { ... }
 }
 

  // Any class whose name matches pattern can be created without new
  @Newify(pattern="[A-Z].*") class MyTreeProcessor {
     final myTree = Tree(Tree(Leaf("A"), Leaf("B")), Leaf("C"))
     final sb = StringBuilder("...")
     def dir = File('.')
     def root = XmlSlurper().parseText(File(dir, sb.toString()).text)
 }
 

or this ("Ruby-style"):

  @Newify class MyTreeProcessor {
     def myTree = Tree.new(Tree.new(Leaf.new("A"), Leaf.new("B")), Leaf.new("C"))
     def process() { ... }
 }
 

After the AST transformation, the following code is passed on for further compilation:

 class MyTreeProcessor {
     def myTree = new Tree(new Tree(new Leaf("A"), new Leaf("B")), new Leaf("C"))
     def process() { ... }
 }
 

The annotation can be used on a whole class as shown above or selectively on a particular method, constructor or field.

The "Ruby-style" new conversions occur automatically unless the 'auto=false' flag is given when using the annotation. You might do this if you create a new method using meta programming.

For the "Python-style" conversions you can either specify each class name on which you want them to apply, or supply a pattern to match class names against. The transformation then works by matching the basename of the provided classes to any similarly named instance method calls not specifically bound to an object, i.e. associated with the 'this' object. In other words Leaf("A") would be transformed to new Leaf("A") but x.Leaf("A") would not be touched.

An example showing how to use the annotation at different levels:

  @Newify(auto=false, value=Foo)
 class Main {
      @Newify // turn auto on for field
     def field1 = java.math.BigInteger.new(42)
     def field2, field3, field4

      @Newify(pattern="[A-z][A-Za-z0-9_]*") // Any class name that starts with an uppercase letter
     def process() {
         field2 = A(Bb(Ccc("my bar")))
     }

      @Newify(Baz)
     Main() {
         field3 = Foo("my foo")
         field4 = Baz("my baz")
     }
 }
 

The annotation is intended to be used sparingly; perhaps in DSL scenarios or when using deeply nested structural types. In particular, there is no support for using the facility with two similarly named classes from different packages at the same time. Though it is OK to have different packages in different contexts. Also, there is no support for turning "Ruby-style" conversions off at the method, constructor or field level if already turned on at the class level.

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
boolean	auto
String	pattern
Class<?>[]	value

Element Detail

value

public abstract Class<?>[] value

Returns:

one or more classes where "Python-style" constructor notation will be supported

Default:

{}

auto

public abstract boolean auto

Returns:

if automatic conversion of "Ruby-style" new method calls should occur

Default:

true

pattern

public abstract String pattern

Returns:

a regex pattern for class names where "Python-style" constructor notation will be supported

Since:

2.5.0

Default:

""