JSNI with backbone structure

Question

I got a question when trying to wrap some Javascript APIs with JSNI of Google Web Toolkit. The javascript API is provided by Parse.com, a cloud based server. My code is like this:

public class MMParseComm {

  private MMProject project = new MMProject();//MMProject has a member: String projectName.

  private String _projectName;

  private native void _retrieveCurrentProject_step1(int projectId) /*-{
    var ProjectList = $wnd.Parse.Object.extend("ProjectList");
    var query = new $wnd.Parse.Query(ProjectList);
    query.equalTo("projectId", projectId);
    query.find({
        success: function(results) {
            //Questions here: In this function, I can access "_projectName" by 
            //[email protected]::_projectName, 
            //but cannot access "project.projectName" using the same syntax.
            //Also, I have searched around but cannot find a way 
            //that can write out a JSON data retrieved in "results" 
            //as a JSONObject in Java.
        },
        error: function(error) {
                $wnd.alert("Error");
        }
    });
  }-*/;
}

As shown on the code above, the questions are in the commented part of the code. I'm not sure how can I write a string in array results out into project.projectName? Also, how can I wrap a JSON data retrieved from results in javascript to be a JSONObject in Java?

Thanks in advance!

Weibin

Answer 1

I don't think the JSNI external call syntax supports chain invocation which is why you can't access project.projectName.

I assume you have a external JavaScript prototype of type Project. You would be better off here creating a overlay type than using the JSONObject API to parse it - it's more efficient and simpler to work with. I'll get you started..

public class MMProject extends JavaScriptObject
{
    protected MMProject () { }

    public final native String getProjectId() /*-{
        return this.projectId;
    }-*/; 
}

Then utilize the wrapper with your success callback.

I suspect that results is probably an array type so your implementation might look like this:

public class MMParseComm
{
    private JsArray<MMProject> projects = null;

    private native void _retrieveCurrentProject_step1(int projectId) /*-{
        var ProjectList = $wnd.Parse.Object.extend("ProjectList");
        var query = new $wnd.Parse.Query(ProjectList);
        query.equalTo("projectId", projectId);
        query.find({
            success: function(results) {
                [email protected]::projects = results;
            },
            error: function(error) {
                $wnd.alert("Error");
            }
        });
    }-*/;
}

Without knowing the specifics of your object model this is the best I can advise you. If you need further clarity I can assist you.