Package groovy.transform.builder

# Class InitializerStrategy

java.lang.Object
org.codehaus.groovy.transform.BuilderASTTransformation.AbstractBuilderStrategy
groovy.transform.builder.InitializerStrategy

All Implemented Interfaces:
  `BuilderASTTransformation.BuilderStrategy`

    public class InitializerStrategy
    extends BuilderASTTransformation.AbstractBuilderStrategy

This strategy is used with the `Builder` AST transform to create a builder helper class for the fluent and type-safe creation of instances of a specified class. It is modelled roughly on the design outlined here: http://michid.wordpress.com/2008/08/13/type-safe-builder-pattern-in-java/ You define classes which use the type-safe initializer pattern as follows:

     import groovy.transform.builder.*
     import groovy.transform.*

     @ToString
     @Builder(builderStrategy=InitializerStrategy) class Person {
         String firstName
         String lastName
         int age
     }

While it isn't required to do so, the benefit of this builder strategy comes in conjunction with static type-checking or static compilation. Typical usage is as follows:

     @CompileStatic
     def main() {
         println new Person(Person.createInitializer().firstName("John").lastName("Smith").age(21))
     }

which prints:

     Person(John, Smith, 21)

If you don't initialise some of the properties, your code won't compile, e.g. if the method body above was changed to this:

     println new Person(Person.createInitializer().firstName("John").lastName("Smith"))

then the following compile-time error would result:

     [Static type checking] - Cannot find matching method Person#<init>(Person$PersonInitializer <groovy.transform.builder.InitializerStrategy$SET, groovy.transform.builder.InitializerStrategy$SET, groovy.transform.builder.InitializerStrategy$UNSET>). Please check if the declared type is correct and if the method exists.

The message is a little cryptic, but it is basically the static compiler telling us that the third parameter, `age` in our case, is unset. You can also add this annotation to your predefined constructors. These will be made private and an initializer will be set up to call your constructor. Any parameters to your constructor become the properties expected by the initializer. If you use such a builder on a constructor as well as on the class or on more than one constructor, then it is up to you to define unique values for 'builderClassName' and 'builderMethodName' for each annotation.

- ## Nested Class Summary

  Nested Classes
  Modifier and Type | Class | Description
  --- | --- | ---
  `static class` | `InitializerStrategy.SET` | Internal phantom type used by the `InitializerStrategy` to indicate that a property has been set.
  `static class` | `InitializerStrategy.UNSET` | Internal phantom type used by the `InitializerStrategy` to indicate that a property remains unset.

  ## Nested classes/interfaces inherited from class org.codehaus.groovy.transform.BuilderASTTransformation.AbstractBuilderStrategy

  `BuilderASTTransformation.AbstractBuilderStrategy.PropertyInfo`

- ## Constructor Summary

  Constructors
  Constructor | Description
  --- | ---
  `InitializerStrategy()` |

- ## Method Summary

  Modifier and Type | Method | Description
  --- | --- | ---
  `void` | `build​(BuilderASTTransformation transform, AnnotatedNode annotatedNode, AnnotationNode anno)` |

  ### Methods inherited from class org.codehaus.groovy.transform.BuilderASTTransformation.AbstractBuilderStrategy

  `checkKnownField, checkKnownProperty, getFields, getIncludeExclude, getPropertyInfoFromBeanInfo, getPropertyInfoFromClassNode, getPropertyInfoFromClassNode, getPropertyInfoFromClassNode, getPropertyInfos, getSetterName, unsupportedAttribute, unsupportedAttribute`

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### InitializerStrategy

    public InitializerStrategy()

- ## Method Details

  - ### build

    public void build​(BuilderASTTransformation transform, AnnotatedNode annotatedNode, AnnotationNode anno)