When to use GWT ensureInjected()?

css, gwt

Solution

As Christian said, inside the UiBinder `ui.xml` file you don't have to worry about invoking `ensureInjected()`, the following XML statements do the job:

<ui:with field='myStyle' type='com...MyStyle'/>

<div class='{myStyle.redBorder}'/>

Of course this is assuming that there is somewhere a `MyStyle` interface defined:

public interface MyStyle {
    public String redBorder();
}

Now I agree with you that things get annoying when you need to manipulate the `CssResource` extension outside of UiBinder templates. Precisely because you have to take care of invoking `ensureInjected()` somewhere before using the `MyStyle` instance with your widgets.

I personally use GIN to inject instances of extensions of `CssResource` whenever I need them.That way you can implement a custom GIN provider ensuring that `ensureInjected()` is called on the `CssResource` before injecting it. There are three steps involved there:

Create an interface for `MyStyle` alongside with a CSS file. MyStyle.java

public interface MyStyle {
    public String redBorder();
}

MyStyle.css

.redBorder { border: 1px solid red; }

Expose it through a `ClientBundle` extension. Resources.java

public interface Resources extends ClientBundle {
    @Source("MyStyle.css")
    public MyStyle style();
}

Configure a GIN provider method to inject your instances of `MyStyle`. ClientModule.java

public class ClientModule extends AbstractGinModule {
    @Override
    protected void configure() {
    //...
    }

    @Provides MyStyle createStyle(final Resources resources) {
        MyStyle style = resources.style();
        style.ensureInjected();
        return style;
    }
}

We smoothly inject the `Resources` instance here above, which means no more hassle of a static accessor calling `GWT.<Resources>create(Resources.class)` anywhere, it just all happens through the GIN injection.

Having done that you can inject your instances of `MyStyle` when you need them. For example (in some MVP context):

private Widget widget;

@Inject
public SomeView(final MyStyle style) {
    //...
    widget = uiBinder.createAndBindUi(this);
    widget.addStyleName(style.redBorder());
}

Problem

I created a few styles into a CSSResource and it works well whether I use ``` GWT.<MyResources>create(MyResources.class).myStyles().ensureInjected(); ``` or not. Could anyone shed a light on this and explain when to use ensureInjected or not? Thank you! Daniel

Original source