topic Re: returned correct array with multiple objects, but array length is 0 - deferred? in ArcGIS Web AppBuilder Questions

returned correct array with multiple objects, but array length is 0 - deferred?

Alexwang — Thu, 25 Aug 2016 04:21:22 GMT

Hello All, I have a simple method to get portal users by a role and put them in an array and return the array. Please see codes below. When I call the method and log the result, the array has two objects. But when i log the length of the result array, i got 0. The length should be 2, why 0 was returned? Is this related to the deferred object? I have no idea how to deal with deferred object. Please help!

results:

Re: returned correct array with multiple objects, but array length is 0 - deferred?

RobertScheitlin__GISP — Sun, 12 Dec 2021 05:42:41 GMT

Alex,

You are checking the length of the array before the deferred has been returned. One way to resolve this is to make your function a deferred as well:

getUsersByRole: function(portal, param) {
    var users = []
    var def = new Deferred;
    portal.queryUsers(param).then(lang.hitch(this, function(items){
        if (items && items.results.length > 0){
            array.forEach(items.results, lang.hitch(this, function(item){
                var u = {};
                u.username = item.username;
                u.fullName = item.fullName;
                users.push(u);
            }));
            def.resolve(users);
        }
    }));
    return def;
},‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

and then simply call your deferred function like this:

portalHandler.getUsersByRole(this._portal, {q: 'role:' + 'org_user'}).then(function(result){
    console.info(result.length);
});‍‍‍

Re: returned correct array with multiple objects, but array length is 0 - deferred?

Alexwang — Thu, 25 Aug 2016 13:30:22 GMT

Worked! Thanks Robert. I have learned a lot from you. Now i know how to deal with a deferred object. But I have another issue if you don't mind to answer it here.

How can I assign the result to a variable under this scope within the call back? Please see codes below. Console outputs null. I can put all the work within the callback, but just wondering assign the result to a this scope variable to be used in other methods.

Re: returned correct array with multiple objects, but array length is 0 - deferred?

RobertScheitlin__GISP — Thu, 25 Aug 2016 13:48:57 GMT

Alex,

Again it is a timing issue as your console.info(this.users) is executing before the deferred has returned.

Re: returned correct array with multiple objects, but array length is 0 - deferred?

Alexwang — Thu, 25 Aug 2016 13:57:48 GMT

thanks Robert. So i have to either put all the logics within the call back, or use deferred again, right?

Re: returned correct array with multiple objects, but array length is 0 - deferred?

RobertScheitlin__GISP — Thu, 25 Aug 2016 14:19:40 GMT

Alex,

Yes or you can call another function from the deferred result that way your code will wait for the deferred execution.