ExtensionAware

Objects that can be extended at runtime with other objects.

// Extensions are just plain objects, there is no interface/type
class MyExtension {
  String foo

  MyExtension(String foo) {
    this.foo = foo
  }
}

// Add new extensions via the extension container
project.extensions.create('custom', MyExtension, "bar")
//                       («name»,   «type»,       «constructor args», …)

// extensions appear as properties on the target object by the given name
assert project.custom instanceof MyExtension
assert project.custom.foo == "bar"

// also via a namespace method
project.custom {
  assert foo == "bar"
  foo = "other"
}
assert project.custom.foo == "other"

// Extensions added with the extensnion container's create method are themselves extensible
assert project.custom instanceof ExtensionAware
project.custom.extensions.create("nested", MyExtension, "baz")
assert project.custom.nested.foo == "baz"

// All extension aware objects have a special “ext” extension of type ExtraPropertiesExtension
assert project.hasProperty("myProperty") == false
project.ext.myProperty = "myValue"

// Properties added to the “ext” extension are promoted to the owning object
assert project.myProperty == "myValue"

Many Gradle objects are extension aware. This includes; projects, tasks, configurations, dependencies etc.

For more on adding & creating extensions, see ExtensionContainer.

For more on extra properties, see ExtraPropertiesExtension.