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I have an empty function that's deregistering my controllers in Angularjs

Using Angularjs 1.6.3, I have a controller like this:
'use strict';
var ngnControllers = angular.module('ngnControllers');
ngnControllers.controller('TestCtrl', ['$scope', '$location', '$http',
function TestCtrl($scope, $location, $http) {
console.log("Before defining $scope.play()");
$scope.play() = function() {
};
console.log("After defining $scope.play()");
}
]);
I copied the $scope.play() function from another controller where it was having the same effect:
When it is not commented out, I get a message saying that the controller is not registered, but that's all. When it is commented out everything works fine.
I am at a loss. Any ideas?

Because your function declaration syntax is wrong and as a result is throwing an error. The error gets caught internally and simply causes the controller registration to fail
Change:
$scope.play() = function() {
To
$scope.play = function() {

You should have empty dependencies added to your module,
var ngnControllers = angular.module('ngnControllers',[]);

Angular doesn't work when defining a service and factory separately

I'm trying to write a simple angular service and a factory like below:
html:
<div ng-controller="mycontroller">
{{saycheese}}
</div>
Javascript
var myApp = angular.module('myApp', []);
myApp.service('myservice', function() {
this.sayHello = function() {
return "from service";
};
});
myApp.factory('myfactory', function() {
return {
sayHello: function() {
return "from factory!"
}
};
});
//defining a controller over here
myapp.controller("mycontroller", ["myfactory", "myservice", function(myfactory, myservice) {
$scope.saycheese = [
myfactory.sayHello(),
myservice.sayHello()
];
}]);
But the JSFiddle still just displays {{saycheese}} instead of angular mapping the function.
Link to my fiddle:
http://jsfiddle.net/PxdSP/3047/
Can you point me where am I going wrong in this case ? Thanks.

You have several syntax errors in your code, and checking the console would have helped without questioning the SO. Here's one possible way to write the controller (demo):
myApp.controller("mycontroller", ["$scope", "myfactory", "myservice",
function($scope, myfactory, myservice) {
$scope.saycheese = [
myfactory.sayHello(),
myservice.sayHello()
];
}]);
Apart from obvious fix myapp => myApp (variable names are case-sensitive in JavaScript), $scope should be passed into controller as an argument (and mentioned as its dependency if using arrayed - proper - form of controller definition, as you did) before you can access it. Otherwise you just get ReferenceError: $scope is not defined exception when controller code is invoked.

Couple things:
myapp.controller(...) should be myApp.controller(...)
You need to inject $scope in your controller.
Fixed controller:
myApp.controller("mycontroller", ["myfactory", "myservice", "$scope", function(myfactory, myservice, $scope) {
$scope.saycheese = [
myfactory.sayHello(),
myservice.sayHello()
];
}]);

Angular: Not able to access variables in controller using service

I am trying to share a variable between a controller and a function. But i get an error from the controller, saying this:
TypeError: Cannot read property 'getSet' of undefined
I have gone through numerous tutorials, but don't know where am I going wrong.
My service code is like this:
app.service('shareData', function() {
var selected = ["plz", "print", "something"];
var putSet = function(set) {
selected = set;
};
var getSet = function() {
return selected;
};
return {
putSet: putSet,
getSet: getSet
};
});
I am able to reach selected from my function defined like this:
setDisplay = function($scope, $mdDialog, shareData) {
console.log(shareData.getSet()); // this is working
$scope.selected = shareData.getSet();
$scope.hide = function() {
$mdDialog.hide();
};
$scope.cancel = function() {
$mdDialog.cancel();
};
$scope.answer = function(answer) {
$mdDialog.hide(answer);
};
};
My controller is like this:
app.controller('topicController', ['$scope', '$http', '$mdDialog', 'shareData',
function ($scope, $http, $mdDialog, $mdToast, shareData) {
console.log(shareData.getSet()); // NOT WORKING
}]);

You had extra $mdToast in your topicController controller's factory function, you need to remove it.
The reason behind it was not working is, currently you had 4 dependency mentioned in array like ['$scope', '$http', '$mdDialog', 'shareData', function & then you are using its instance inside the function next to DI array. Inside that function you had actually 5 dependencies where $mdToast extra. So behind the scene what happening is $scope of function hold an value of '$scope' DI array likewise you go right to left. But when it comes to $mdToast(in controller function) it was holding a value of 'shareData'(of DI array) & then the next parameter shareData get nothing.
app.controller('topicController', ['$scope', '$http', '$mdDialog', 'shareData',
function ($scope, $http, $mdDialog, shareData) { //<--removed $mdToast
console.log(shareData.getSet());
}
]);
NOTE: You are using DI inline array annotation, so the sequence in which dependency are injected in array, in same sequence you should
inject then in underlying factory function.

How to construct Controller name from route in angularjs

I am trying to define a generic route which will handle most of request. Adding a route for each and every feature addition is what I feel not good and not maintainable.
So my target is to write a generic route and resolve the decencies dynamically, which include resolving all dependent controller & service files, resolving templateUrl and resolving controller name. I can resolve/construct everything except controller name. Please help me a way around
My route with a custom resolver:
$routeProvider
.when('/:module/:controller/:action?', routeResolver.resolve())
Inside my custom resolver:
function routeResolverProvider(){
this.$get= function(){
return this;
}
this.resolve = function (options) {
var route = {};
route.templateUrl = function (params) {
var path = String.format('/app/components/{0}/{1}.view.html', params.module, params.controller);
return path;
};
//================================================================================
route.controller='THIS IS WHAT I WANT TO CONSTRUCT FROM ROUTE as templateUrl'
//================================================================================
route.resolve = {
loadDependencies: ['$q', '$rootScope', '$route', function ($q, $rootScope, $route) {
// MY RESOLVE LOGIC HERE
// I construct dependent file path from route values
// String.format('/app/components/{0}/{1}.controller.js', params.module, params.controller);
}]
};
return route;
}}
app.provider('routeResolver', routeResolverProvider)
Some good articles:
https://github.com/angular/angular.js/wiki/Understanding-Dependency-Injection
https://medium.com/opinionated-angularjs/advanced-routing-and-resolves-a2fcbf874a1c

If I understand your question correctly, then you want to be able to instantiate a controller by name.
This is possible in AngularJS as explained under Testing Controllers.
You have to use the $controller service like this:
$scope = $rootScope.$new();
$controller('NamedController', {$scope: $scope});
Here is a working plunker: http://plnkr.co/edit/AVCEdLS9zhIzCyZgcXZF?p=preview

Thanks a lot Dan, I was looking exactly for this kind also. So I modify my resolver as and finally its bingo.
this.$get = ['$rootScope', '$scope', '$route', '$controller', function () {
return this;
}];
route.controller = function ($rootScope, $scope, $route, $controller) {
var params = $route.current.params;
$controller(params.controller.toLowerCase() + 'Controller', {$scope: $scope});
}
Finally I solved my issue but would like to discuss the possible disadvantages of this approach.

AngularJS $rootScope variable exists, but not accessible

I set a $rootScope variable in one of my modules and now want to access that same $rootScope variable in another module. Thus far I can see that in both modules the variable has been set properly, but when I try accessing the variable in $rootScope, I only get undefined.
How can I access this variable without doing a factory/service workaround? The variable is really simple and $rootScope should suffice for what I need. I've put some generic sample code below to illustrate the issue:
file1.js
var app = angular.module('MyApp1', []);
app.controller('Ctrl1', ['$scope', '$rootScope', function($scope, $rootScope) {
$scope.myFunc = function() {
$rootScope.test = 1;
}
}
file2.js
var app = angular.module('MyApp2', []);
app.controller('Ctrl2', ['$scope', '$rootScope', function($scope, $rootScope) {
$scope.need_to_access_this = $rootScope.test; // undefined
console.log($rootScope); // returns JS object w/ test property set to 1
}

I was just stuck in the same problem when I figured out that you have define those properties for $rootScope before the controllers or services load. So what I did was set inital values when the application runs. In your case it will be like:
app.run(function($rootScope){
$rootScope.test="variable";
})
`

In Ctrl1 the $rootScope.test value is set inside the $scope.myFunc.
The problem is that you aren't calling that function, so the test property in $rootScope is never set.
You need to call $scope.myFunc(); in Ctrl1 or set $rootScope.test = 1; dirrectly in the Controller:
app.controller('Ctrl1', ['$scope', '$rootScope', function($scope, $rootScope) {
$scope.myFunc = function() {
$rootScope.test = 1;
};
$scope.myFunc();
}
or
app.controller('Ctrl1', ['$scope', '$rootScope', function($scope, $rootScope) {
$rootScope.test = 1;
}
EDIT:
The above suggestions still remain valid, thus you need to call myFunc().
But the problem with your code is that Ctrl1 belongs to MyApp1 and Ctrl2 belongs to MyApp2.
Every application has a single root scope (docs here)
You will need to create Ctrl2 as a controller of MyApp1:
angular.module('MyApp1')
.controller('Ctrl2', ['$scope', '$rootScope', function($scope, $rootScope) {
$scope.need_to_access_this = $rootScope.test; // undefined
console.log($rootScope); // returns JS object w/ test property set to 1
}]);