Detecting Mappings in Components

You can detect whether a component is part of a Polymer template using the isTemplateMapped method.

This is useful if you want to execute custom logic depending on whether the component was mapped in a template (injected via the @Id or @Uses annotations) or created directly using one of its constructors, for example.

Example: Calling the isTemplateMapped method in MyComponent.

Java

@Tag("div")
public class MyComponent extends Div {
  public MyComponent() {
    if (!isTemplateMapped()) {
      getElement().getStyle().set("color", "red");
    }
  }
}

• By default, the component only sets a style when the component is not part of a template.

See Binding Components from a PolymerTemplate for more about To @Id mappings.