FatFractal grabBagAdd() -- Error 400: Cannot add NULL items to a object's grab bag

Question

I am getting an error when calling the grabBagAdd() method using the FatFractal JavaScript (HTML5) SDK. For this particular problem, my data model is simple, and only involves two object types: a custom Team object and the default FFUser object.

Relevant FFDL Declarations:

CREATE OBJECTTYPE FFUser (userName STRING, firstName STRING, lastName STRING, email STRING, active BOOLEAN, authDomain STRING, groups GRABBAG /FFUserGroup, notif_ids GRABBAG /FFNotificationID)
CREATE OBJECTTYPE Team (teamName STRING, members GRABBAG /FFUser)

CREATE COLLECTION /FFUser OBJECTTYPE FFUser
CREATE COLLECTION /Teams OBJECTTYPE Team

JS Object Declarations:

function Team(data){
    if(data){
        this.clazz = data.clazz;
        this.guid = data.guid;
        this.teamName = data.teamName;
    }
    else{
        this.clazz = "Team";
        this.guid = null;
        this.teamName = null;
    }
    return this;
}

function FFUser(data){
    if(data){
        this.clazz = data.clazz;
        this.userName = data.userName;
        this.firstName = data.firstName;
        this.lastName = data.lastName;
        this.email = data.email;
        this.active = data.active;
        this.guid = data.guid;
    }
    else{
        this.clazz = "FFUser";
        this.userName = null;
        this.firstName = null;
        this.lastName = null;
        this.email = null;
        this.active = null;
        this.guid = null;
    }
    return this;
}

I'm simply attempting to add an FFUser to a selected Team's members grab bag. I am using KnockoutJS bindings to display my web app's data and KnockoutJS observables to store the data locally. The pertinent steps in the use case generating the error are as follows:

Pull Teams from my app's back-end after user logs in. Below, self.teams is an observable array which is bound to an HTML select menu.

    function loadTeams() {
        ff.getArrayFromUri("/ff/resources/Teams",function(loadedTeams) {
            if(loadedTeams.length > 0) {
                for(var i = 0; i < teams.length; i++) {
                    var team = new Team(loadedTeams[i]);
                    self.teams.push(team);
                }
            }
            else console.log("No teams to load!");
        },function(statusCode,responseText) {
            alert(JSON.parse(responseText).statusMessage);
        });
    };

The user selects a team from the select menu and enters a username to add as a team member. Upon submission, the grabBagAdd() is executed. Below, self.selectedTeam is an observable bound to the value of the select menu and contains one of the Team objects from self.teams. Also, self.addMemberEmail is an observable bound to the value of the username input box.

    self.addMember = function() {
        if(self.addMemberEmail()) {
            ff.getObjFromUri("/ff/resources/FFUser/(userName eq '" + self.addMemberEmail() + "')",function(user) {
                if(user){
                    var member = new FFUser(user);
                    ff.grabBagAdd(member,self.selectedTeam(),"members",function() {
                        console.log("Added member to grabbag!");
                    },function(statusCode,responseText) {
                        alert(JSON.parse(responseText).statusMessage);
                    });         
                }
                else alert("No users found with the provided username.");
            },function(statusCode,responseText) {
                alert(JSON.parse(responseText).statusMessage);
            });
        }
        else alert("Must provide member email.");
    };

FatFractal returns a 400: Bad Request error as follows:

FatFractal.handleGrabBagRequest 400, {"result":null,"statusMessage":"Cannot add NULL items to a object's grab bag"}

Not sure what to make of the error. Any help would be appreciated!

Answer 1

The grabBagAdd function takes ffUrls, not the objects themselves, as the first two arguments. So, try the following:

ff.grabBagAdd(member.ffUrl, self.selectedTeam().ffUrl, "members", ...

From your question, it's not completely clear that self.selectedTeam() will return an object with metadata, but anyway you get the idea.