Block meteor helper from returning when doing http request

Question

I need to prevent my meteor helper from returning right away until either the timeout or data returns from my Meteor.http.get(url, ...) request. For example,

Meteor.templateName.helpers ({
    testHelper: function()
         {
          var ss = "doesnt wait";
               Meteor.http.get("http://api.somesite.com",
                    function (error, result) {
                        if(!error){
                           if(result.statusCode === 200) {
                              var respJson = JSON.parse(result.content);
                              console.log(respJson);
                              ss =  "should have this value";
                          }
                      }
                  });

               return ss;
          }

     })

Is Meteor.http not a blocking call, how can i make the helper method stop until the get request returns data. Do i need to move the get request to a Meteor.Method ?

Answer 1

On the client, you don't have the fiber module, as a result is not possible to make a synchronous call to a function. One solution might be to use a Session because of it's reactivity. You just set a default value, and use it in your helper function

Session.setDefault('testHelper', {msg: 'wait'})
Meteor.templateName.helpers ({
    testHelper: function() {
        return Session.get('testHelper');
    }
});

Then update this session every time you want:

Template.templateName.rendered = function () {
    Meteor.http.get("http://api.somesite.com",
        function (error, result) {
            if(!error && result.statusCode === 200){
                var respJson = JSON.parse(result.content);
                Session.set('testHelper', respJson)
            }
        }
    );
}

If you don't want to use a Session, you can implement your own reactivity mecanism using the Deps module. For instance in the Meteor.http.get callback you can set a Template.templateName attribute and invalidate a context object in order to rerun the helper function. But a Session is definitly more easy ;-)