# ExtensionAware

API Documentation: | `ExtensionAware`

Known Subtypes: |
`Project` | `Gradle` | `Settings`
`DependencyHandler` | `Task` | `SourceSet`

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 extension 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`.

An `ExtensionAware` object has several 'scopes' that Gradle searches for properties. These scopes are:

- The object itself. This scope includes any property getters and setters declared by the implementation class. The properties of this scope are readable or writable depending on the presence of the corresponding getter or setter method.
- Groovy Meta-programming methods implemented by the object's class, like `propertyMissing()`. Care must be taken by plugin authors to ensure `propertyMissing()` is implemented such that if a property is not found a MissingPropertyException(String, Class) exception is thrown. If `propertyMissing()` always returns a value for any property, Gradle will not search the rest of the scopes below.
- The extra properties of the object. Each object maintains a map of extra properties, which can contain any arbitrary name -> value pair. Once defined, the properties of this scope are readable and writable.
- The extensions added to the object by plugins. Each extension is available as a read-only property with the same name as the extension.

### Properties

Property | Description
`extensions` | The container of extensions.

### Methods

No methods

### Script blocks

No script blocks

### Property details

#### `ExtensionContainer` `extensions` (read-only)

The container of extensions.