[Java] Annotation Type NamedVariant
- groovy.transform.NamedVariant
Allows construction of a named-arg equivalent method or constructor. The method or constructor will have at least a first argument of type Map
and may have more arguments. As such, it can be called using Groovy's named-arg syntax. The original method/constructor is retained and is called by the generated method/constructor. One benefit of this approach is the potential for improved type checking. The annotated "tuple" method/constructor can be type rich and will be checked as such during normal compilation. The generated method/constructor using the map argument will be named-argument friendly but the map also hides type information. The generated method however contains no business logic so the chance of errors is minimal. Any arguments identified as named arguments will be supplied as part of the map. Any additional arguments are supplied in the normal tuple style. Named parameters are identified in one of three ways:
- Use one or more
@NamedParam
annotations to explicitly identify such parameters - Use one or more
@NamedDelegate
annotations to explicitly identify such parameters as delegate parameters - If no parameters with
@NamedParam
or@NamedDelegate
annotations are found then:- If
autoDelegate
is false (the default), all parameters are treated as if they were named parameters - If
autoDelegate
is true, the first parameters is treated as if it was a delegate parameter
- If
@NamedParam
and @NamedDelegate
annotations. Named arguments will be supplied via the map with their property name (configurable via annotation attributes within @NamedParam
) being the key and value being the argument value. For named delegates, any properties of the delegate can become map keys. Duplicate keys across delegate properties or named parameters are not allowed. The type of delegate parameters must be compatible with Groovy's as
cast operation from a Map
. Here is an example using implicit named parameters.
import groovy.transform.*
@NamedVariant
int makeSense(int dollars, int cents) {
100 * dollars + cents
}
assert makeSense(dollars: 2, cents: 50) == 250
Here is an example using a delegate parameter. import groovy.transform.*@ToString(includeNames=true)
class Color { Integer r, g, b }@NamedVariant
String foo(
- NamedDelegate:
- Color shade) { shade } def result = foo(g: 12, b: 42, r: 12) assert result.toString() == 'Color(r:12, g:12, b:42)' You could also explicitly annotate the
shade
argument with the@NamedDelegate
annotation if you wanted. The generated method will be something like this:String foo(Map args) { return foo(args as Color) }
The generated method/constructor retains the visibility and return type of the original method/constructor but the VisibilityOptions annotation can be added to customize the visibility. You could have the annotated method/constructor private for instance but have the generated one be public.
- See Also:
- VisibilityOptions
- NamedParam
- NamedDelegate
- Since:
- 2.5.0
Element Summary
Type | Name and Description |
---|---|
boolean |
autoDelegate If true, add an implicit
|
String |
visibilityId If specified, must match the optional "id" attribute in an applicable VisibilityOptions annotation. |
Inherited Methods Summary
Methods inherited from class | Name |
---|---|
class Object | wait, wait, wait, equals, toString, hashCode, getClass, notify, notifyAll |
Element Detail
public boolean autoDelegate
If true, add an implicit
- NamedDelegate:
- to the first parameter if no
- NamedDelegate:
- or
- NamedParam:
- annotations are found on any parameter.
- Since:
- 2.5.3
public String visibilityId
If specified, must match the optional "id" attribute in an applicable VisibilityOptions
annotation. @default Undefined.STRING
© 2003-2020 The Apache Software Foundation
Licensed under the Apache license.
https://docs.groovy-lang.org/2.5.14/html/gapi/groovy/transform/NamedVariant.html