Angular ngresource update method not a function

I am using the MEAN Stack. I am trying to add a PUT request into my $ngResource and I get an error:

TypeError: conService.update is not a function

at m.$scope.joinCon (http://localhost:3000/javascripts/chirpApp-ngresource.js:217:14)

at lb.functionCall (https://ajax.googleapis.com/ajax/libs/angularjs/1.3.16/angular.min.js:200:64)

at Hc.(anonymous function).compile.d.on.f (https://ajax.googleapis.com/ajax/libs/angularjs/1.3.16/angular.min.js:216:394)

at m.$get.m.$eval (https://ajax.googleapis.com/ajax/libs/angularjs/1.3.16/angular.min.js:126:250)

at m.$get.m.$apply (https://ajax.googleapis.com/ajax/libs/angularjs/1.3.16/angular.min.js:126:476)

at HTMLButtonElement.<anonymous> (https://ajax.googleapis.com/ajax/libs/angularjs/1.3.16/angular.min.js:216:446)

at HTMLButtonElement.c (https://ajax.googleapis.com/ajax/libs/angularjs/1.3.16/angular.min.js:32:389)

My code

//My factory
app.factory('conService', function ($resource) {return $resource('/api/cons', {'update': { method: 'PUT' }});});

//My update
conService.update({conName:$scope.cons.conName},$scope.cons);};

//My api to get all conventions
.get(function (req, res) {Con.find(function (err, cons) {if (err) { return res.send(500, err); }return res.send(cons);});})

Can anyone help me figure out what I am missing in my update? Thanks

Since it's a factory you should instantiate in controller code before usage it with following:

var cs = new conService();
cs.update(/*params here*/);

For more details read those great posts: AngularJS: Service vs provider vs factory, AngularJS : Factory and Service?