Package groovy.transform

Annotation Interface ImmutableBase

@Documented @Retention(SOURCE) @Target(TYPE) public @interface ImmutableBase
Class annotation used to assist in the creation of immutable classes. Checks on the validity of an immutable class and makes some preliminary changes to the class. Usually used via the @Immutable meta annotation.

Custom property handling:

  • The @ImmutableBase annotation supports customization using @PropertyOptions which allows a custom property handler to be defined. This is most typically used behind the scenes by the @Immutable meta-annotation but you can also define your own handler. If a custom handler is present, it will determine the code generated for the getters and setters of any property.
Since:
2.5.0
See Also:

  • Optional Element Summary

    Optional Elements
    Modifier and Type
    Optional Element
    Description
    boolean
    copyWith
    If true, this adds a method copyWith which takes a Map of new property values and returns a new instance of the Immutable class with these values set.

  • Element Details

    • copyWith

      boolean copyWith
      If true, this adds a method copyWith which takes a Map of new property values and returns a new instance of the Immutable class with these values set. Example: 
       @groovy.transform.Immutable(copyWith = true)
 class Person {
     String first, last
 }

 def tim   = new Person( 'tim', 'yates' )
 def alice = tim.copyWith( first:'alice' )

 assert tim.first   == 'tim'
 assert alice.first == 'alice'
      Unknown keys in the map are ignored, and if the values would not change the object, then the original object is returned.

      A key may also be a dotted nested path — copyWith then returns a new instance with that nested value updated, reusing the untouched branches (identity is preserved transitively): 

       @groovy.transform.Immutable(copyWith = true) class Address { String city, zip }
 @groovy.transform.Immutable(copyWith = true) class Person  { String name; Address address }

 def p = new Person('Alice', new Address('NYC', '10001'))
 def q = p.copyWith('address.city': 'Boston')
 assert q.address.city == 'Boston'
 assert q.address.zip  == '10001'
      Every node on a nested path must itself provide copyWith(Map) (e.g. an @Immutable/@RecordType declared with copyWith=true); otherwise a clear error is raised.

      A transactional block form is also generated, sugar over the map form. Within it, old is the original (pre-state) object — aligning with old in @Ensures/@Contract — so values may be derived from it; prop.modify { } is a shorthand for the common transform-this-same-field case: 

       def q = p.copyWith {
     name = 'Bob'                              // plain set
     address.city = old.address.city.reverse() // derive from pre-state
     loginCount.modify { it + 1 }              // single-field shorthand
 }
      On a navigated path modify is reserved by the block, so use the old form (x = old.x.modify { ... }) to call a real same-named method on the value type — or simply when .modify would read confusingly. If a method called copyWith that takes a single parameter already exists in the class, then this setting is ignored, and no method is generated.
      Default:
      false