Package: groovy.transform

## [Java] Annotation Type TupleConstructor

- groovy.transform.TupleConstructor

-     @Documented
      @Retention(RetentionPolicy.SOURCE)
      @Target(ElementType.TYPE)
      @GroovyASTTransformationClass("org.codehaus.groovy.transform.TupleConstructorASTTransformation")
      public @interface TupleConstructor

  Class annotation used to assist in the creation of tuple constructors in classes. If the class is also annotated with `@ImmutableBase`, then the generated constructor will contain additional code needed for immutable classes. Should be used with care with other annotations which create constructors - see "Known Limitations" for more details.

  It allows you to write classes in this shortened form:

       @groovy.transform.TupleConstructor class Customer {
           String first, last
           int age
           Date since
           Collection favItems
       }
       def c1 = new Customer(first:'Tom', last:'Jones', age:21, since:new Date(), favItems:['Books', 'Games'])
       def c2 = new Customer('Tom', 'Jones', 21, new Date(), ['Books', 'Games'])
       def c3 = new Customer('Tom', 'Jones')

  The `@TupleConstructor` annotation instructs the compiler to execute an AST transformation which adds the necessary constructor method to your class.

  A tuple constructor is created with a parameter for each property (and optionally field and super properties). The default order is properties, pseudo/JavaBean properties and then fields for parent classes first (if includeSuperXxx annotation attributes are used). A default value is provided (using Java's default values) for all parameters in the constructor. Groovy's normal conventions then allows any number of parameters to be left off the end of the parameter list including all of the parameters - giving a no-arg constructor which can be used with the map-style naming conventions.

  The order of parameters is given by the properties of any super classes (if `includeSuperProperties` is set) with the most super first followed by the properties of the class followed by the fields of the class (if `includeFields` is set). Within each grouping the order is as attributes appear within the respective class.

  More examples:

       //--------------------------------------------------------------------------
       import groovy.transform.TupleConstructor

       @TupleConstructor()
       class Person {
           String name
           List likes
           private boolean active = false
       }

       def person = new Person('mrhaki', ['Groovy', 'Java'])

       assert person.name == 'mrhaki'
       assert person.likes == ['Groovy', 'Java']

       person = new Person('mrhaki')

       assert person.name == 'mrhaki'
       assert !person.likes

       //--------------------------------------------------------------------------
       // includeFields in the constructor creation.
       import groovy.transform.TupleConstructor

       @TupleConstructor(includeFields=true)
       class Person {
           String name
           List likes
           private boolean active = false

           boolean isActivated() { active }
       }

       def person = new Person('mrhaki', ['Groovy', 'Java'], true)

       assert person.name == 'mrhaki'
       assert person.likes == ['Groovy', 'Java']
       assert person.activated

       //--------------------------------------------------------------------------
       // use force attribute to force creation of constructor
       // even if we define our own constructors.
       import groovy.transform.TupleConstructor

       @TupleConstructor(force=true)
       class Person {
           String name
           List likes
           private boolean active = false

           Person(boolean active) {
               this.active = active
           }

           boolean isActivated() { active }
       }

       def person = new Person('mrhaki', ['Groovy', 'Java'])

       assert person.name == 'mrhaki'
       assert person.likes == ['Groovy', 'Java']
       assert !person.activated

       person = new Person(true)

       assert person.activated

       //--------------------------------------------------------------------------
       // include properties and fields from super class.
       import groovy.transform.TupleConstructor

       @TupleConstructor(includeFields=true)
       class Person {
           String name
           List likes
           private boolean active = false

           boolean isActivated() { active }
       }

       @TupleConstructor(callSuper=true, includeSuperProperties=true, includeSuperFields=true)
       class Student extends Person {
           List courses
       }

       def student = new Student('mrhaki', ['Groovy', 'Java'], true, ['IT'])

       assert student.name == 'mrhaki'
       assert student.likes == ['Groovy', 'Java']
       assert student.activated
       assert student.courses == ['IT']

  Custom visibility:

  - The `@TupleConstructor` annotation generates a public constructor unless an applicable VisibilityOptions annotation is also present. It can be useful to change the visibility if you want to also create a builder or provide your own static factory method for object creation. You can make the constructor private and access it from the builder or your factory method. (Note: you'll probably want to use `@CompileStatic` in conjunction with such an approach since dynamic Groovy currently gives the ability to access even private constructors.)
  - An optional `visibilityId` attribute can be specified. If present, it must match the optional `id` attribute of an applicable `VisibilityOptions` annotation. This can be useful if multiple `VisibilityOptions` annotations are needed.

  Custom property handling:

  - The `@TupleConstructor` 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 when initializing any property (or field).

  Named-argument support:

  - Groovy supports named-arguments for classes with a no-arg constructor or a constructor with a Map as the first argument. This is compatible with the default kind of constructor(s) that `@TupleConstructor` produces.
  - If the `defaults` annotation attribute is set to `false`, and no other map-based constructor are added then named-argument processing will not be available.
  - If there is more than one included property (and/or field) and the first property (or field) has type Object, AbstractMap, Map or HashMap, then a special `LinkedHashMap` constructor will be created in addition to the tuple constructor to support named parameters in the normal way. This won't be created if the class is already annotated with `@MapConstructor` or if the `defaults` annotation attribute is set to `false`.
  - If the first property (or field) has type `LinkedHashMap` or if there is a single Object, AbstractMap, Map or HashMap property (or field), then no additional constructor will be added and Groovy's normal map-style naming conventions will not be available.

  Known limitations/special cases:

  - This AST transform might become a no-op if you are defining your own constructors or combining with other AST transforms which create constructors (e.g. `@InheritConstructors`); the order in which the particular transforms are processed becomes important in that case. See the `force` attribute for further details about customizing this behavior.
  - This AST transform normally uses default parameter values which creates multiple constructors under the covers. You should use with care if you are defining your own constructors or combining with other AST transforms which create constructors (e.g. `@InheritConstructors`); the order in which the particular transforms are processed becomes important in that case. See the `defaults` attribute for further details about customizing this behavior.
  See Also:
    PropertyOptions
    VisibilityOptions
  Since:
    1.8.0

- - ### Element Summary

    Optional Element Summary
    Type | Name and Description
    --- | ---
    `boolean` | `allNames` Whether to include all fields and/or properties within the constructor, including those with names that are considered internal.
    `boolean` | `allProperties` Whether to include all properties (as per the JavaBean spec) in the generated constructor.
    `boolean` | `callSuper` Should super properties be called within a call to the parent constructor rather than set as properties.
    `boolean` | `defaults` Used to set whether default value processing is enabled (the default) or disabled.
    `DefaultsMode` | `defaultsMode` Used to set the mode for default value processing.
    `String[]` | `excludes` List of field and/or property names to exclude from the constructor.
    `boolean` | `force` By default, this annotation becomes a no-op if you provide your own constructor.
    `boolean` | `includeFields` Include fields in the constructor.
    `boolean` | `includeProperties` Include properties in the constructor.
    `boolean` | `includeSuperFields` Include visible fields from super classes in the constructor.
    `boolean` | `includeSuperProperties` Include properties from super classes in the constructor.
    `String[]` | `includes` List of field and/or property names to include within the constructor.
    `boolean` | `namedVariant` If true, add a map-based named-arg variant.
    `Class` | `post` A Closure containing statements which will be appended to the end of the generated constructor.
    `Class` | `pre` A Closure containing statements which will be prepended to the generated constructor.
    `boolean` | `useSetters` By default, properties are set directly using their respective field.
    `String` | `visibilityId` If specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.

  - ### Inherited Methods Summary

    Inherited Methods
    Methods inherited from class | Name
    --- | ---
    `class Object` | `equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Element Detail

    - #### public boolean allNames

      Whether to include all fields and/or properties within the constructor, including those with names that are considered internal.

      Since:
        2.5.0
      Default:
        false

    - #### public boolean allProperties

      Whether to include all properties (as per the JavaBean spec) in the generated constructor. When true, Groovy treats any explicitly created setXxx() methods as property setters as per the JavaBean specification. JavaBean properties come after any Groovy properties but before any fields for a given class (unless 'includes' is used to determine the order).

      Since:
        2.5.0
      Default:
        false

    - #### public boolean callSuper

      Should super properties be called within a call to the parent constructor rather than set as properties. Typically used in combination with `includeSuperProperties`. Can't be true if using `pre` with a `super` first statement.

      Default:
        false

    - #### public boolean defaults

      Used to set whether default value processing is enabled (the default) or disabled. Ignored if an explicit value is given for `defaultsMode()`.

      By default, every constructor parameter is given a default value. This is the equivalent of DefaultsMode.ON.

      When set to false, default values are not allowed for properties and fields. This is the equivalent of DefaultsMode.OFF.

      Since:
        2.5.0
      Default:
        true

    - #### public DefaultsMode defaultsMode

      Used to set the mode for default value processing.

      When set to `ON` (the default value), every constructor parameter is given a default value. This value will be Java's default for primitive types (zero or false) and null for Objects, unless an initial value is given when declaring the property or field. A consequence of this design is that you can leave off parameters from the right if the default value will suffice. As far as Java interoperability is concerned, Groovy will create additional constructors under the covers representing the constructors with parameters left off, all the way from the constructor with all arguments to the no-arg constructor.

      When set to `AUTO`, default values are catered for where explicit default values are given for the respective property/field. Additional positional constructors are generated as per Groovy's normal default value processing. Properties/fields with an explicit initial value are deemed optional and may be dropped. Properties/fields with no initial value are deemed mandatory and must be supplied as an argument to the respective constructor. Optional arguments to a positional constructor are dropped from the right.

      When set to `OFF`, default values are not allowed for properties and fields. Only the constructor containing all arguments will be provided. In particular, a no-arg constructor won't be provided and since this is currently used by Groovy when using named-arguments, the named-argument style won't be available.

      Since:
        4.0.0
      Default:
        DefaultsMode.ON

    - #### public String[] excludes

      List of field and/or property names to exclude from the constructor. Must not be used if 'includes' is used. For convenience, a String with comma separated names can be used in addition to an array (using Groovy's literal list notation) of String values.

      Default:
        {}

    - #### public boolean force

      By default, this annotation becomes a no-op if you provide your own constructor. By setting `force=true` then the tuple constructor(s) will be added regardless of whether existing constructors exist. It is up to you to avoid creating duplicate constructors.

      Default:
        false

    - #### public boolean includeFields

      Include fields in the constructor. Fields come after any properties.

      Default:
        false

    - #### public boolean includeProperties

      Include properties in the constructor.

      Default:
        true

    - #### public boolean includeSuperFields

      Include visible fields from super classes in the constructor. Groovy properties, JavaBean properties and fields (in that order) from superclasses come before the members from a subclass (unless 'includes' is used to determine the order).

      Default:
        false

    - #### public boolean includeSuperProperties

      Include properties from super classes in the constructor. Groovy properties, JavaBean properties and fields (in that order) from superclasses come before the members from a subclass (unless 'includes' is used to determine the order).

      Default:
        false

    - #### public String[] includes

      List of field and/or property names to include within the constructor. The order of inclusion is determined by the order in which the names are specified. Must not be used if 'excludes' is used. For convenience, a String with comma separated names can be used in addition to an array (using Groovy's literal list notation) of String values. The default value is a special marker value indicating that no includes are defined; all fields are included if includes remains undefined and excludes is explicitly or implicitly an empty list.

      Default:
        { Undefined.STRING }

    - #### public boolean namedVariant

      If true, add a map-based named-arg variant. Similar to using `@MapConstructor` but handles just the parameters handled by the generated tuple constructor. Setting `namedVariant=true` is incompatible with using `@MapConstructor`.

      Since:
        4.0.0
      Default:
        false

    - #### public Class post

      A Closure containing statements which will be appended to the end of the generated constructor. Useful for validation steps or tweaking the populated fields/properties.

      Since:
        2.5.0
      Default:
        Undefined.CLASS.class

    - #### public Class pre

      A Closure containing statements which will be prepended to the generated constructor. The first statement within the Closure may be `super(someArgs)` in which case the no-arg super constructor won't be called.

      Since:
        2.5.0
      Default:
        Undefined.CLASS.class

    - #### public boolean useSetters

      By default, properties are set directly using their respective field. By setting `useSetters=true` then a writable property will be set using its setter. If turning on this flag we recommend that setters that might be called are made null-safe wrt the parameter.

      Since:
        2.5.0
      Default:
        false

    - #### public String visibilityId

      If specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.

      Since:
        2.5.0
      Default:
        Undefined.STRING