Directive controllerAs and scope

[facultymatt]

When using multiple directives that use the controllerAs: 'vm' syntax and do not have scope, they will conflict and vm will get overwritten. For example, the following directives will not work as expected:

angular
    .module('app')
    .directive('myExampleOne', myExampleOne);

function myExampleOne() {
    var directive = {
        templateUrl: 'app/feature/example.directiveOne.html',
        controllerAs: 'vm',
        bindToController: true 
    };
    return directive;
}

angular
    .module('app')
    .directive('myExampleTwo', myExampleTwo);

function myExampleTwo() {
    var directive = {
        templateUrl: 'app/feature/example.directiveTwo.html',
        controllerAs: 'vm',
        bindToController: true 
    };
    return directive;
}

A few questions here:

1. Does it make sense to always use scope? scope: {} or even scope: true will fix this issue. In my experience this is good practice to avoid scope conflicts even sans controllerAs.
2. Should we not use bindToController in these examples?

Related style

https://github.com/johnpapa/angular-styleguide#style-y075

[lunks]

I'd say that it is a good practice to always create a new scope for directives.

[jansepke]

using only isolated scopes, gives you more control over the dataflow of your application. and yes since angular 1.4 you should always use bindToController with isolated scopes and controllerAs.

[lunks]

Any changes on angular 1.4 that makes this different than 1.3, @Jandalf?

[jansepke]

@lunks yes bindToController supports now an object value to follow the angular 2 binding style

e.g.: scope: {}, bindToController {param1: '='}

see #543

[karlhorky]

Are isolated scopes not bad for composability (more directives on one element)? Since Angular 1.2 there is an error Multiple Directive Resource Contention when using multiple directives with isolated scopes. For instance:

<input my-directive my-second-directive ng-model="title">

angular.module('app', []).directive('myDirective', function () {
  return {
    restrict: 'A',
    scope: {}
  };
}).directive('mySecondDirective', function () {
  return {
    restrict: 'A',
    scope: {}
  };
});

Demo on Plunker

Resulting error: https://docs.angularjs.org/error/$compile/multidir?p0=myDirective&p1=mySecondDirective&p2=new%2Fisolatedundefinedcope&p3=undefined

[karlhorky]

I've opened #608 for an answer to this.

[karlhorky]

For this reason I would like an alternative answer to this question though - without using isolated scope. One thing I can imagine is to rename controllerAs based on the directive name.

angular
    .module('app')
    .directive('myExampleOne', myExampleOne);

function myExampleOne() {
    var directive = {
        templateUrl: 'app/feature/example.directiveOne.html',
        controllerAs: 'myExampleOneVm',
        bindToController: true 
    };
    return directive;
}

angular
    .module('app')
    .directive('myExampleTwo', myExampleTwo);

function myExampleTwo() {
    var directive = {
        templateUrl: 'app/feature/example.directiveTwo.html',
        controllerAs: 'myExampleTwoVm',
        bindToController: true 
    };
    return directive;
}

This would still not solve nested directives of the same type though...