Use Mixin property in a Controller - ember.js

Question

This is a crappy example, but I am merely trying to use a mixin's property in a controller. I did the same thing in a route and could access that property. I've tried every way to reference a property I know... What am I misunderstanding?
// app/mixins/author-data.js
import Ember from 'ember';
export default Ember.Mixin.create({
authorName: 'Example author name',
});
// app/controllers/application.js
import Ember from 'ember';
import AuthorDatas from 'app-name/mixins/author-data';
export default Ember.Controller.extend(AuthorDatas, {
siteTitle: `Site title`,
fromAuthorData: this.get('authorName'),
// returns 💩 - what is the proper syntax?
actions: {
showAuthor() {
var author = this.get('fromAuthorData');
console.log(`Author from controller: ${author}`);
},
},
});
// app/templates/application.hbs
{{fromAuthorData}}
This works...
// app/routes/application.js
import Ember from 'ember';
import AuthorDatas from 'app-name/mixins/author-data';
export default Ember.Route.extend(AuthorDatas, {
afterModel() { // arbitrary
var intro = `Author from route:`;
console.log(`${intro} this.authorName`, this.authorName );
console.log(`${intro} this.get('author-name')`, this.get('authorName') );
},
});
(I would have made an ember-twiddle - but I wasn't sure if Mixins would work the same way ~ since they aren't on the list and there is 0 documentation)

Answer 1

The fromAuthorData property on your controller should be defined like this (I think):
fromAuthorData: Ember.computed('authorName', function() {
return this.get('authorName'); // or whatever derived value you need
}

Answer 2

To understand the problem we need to talk about scope, when you extend/create an object you are merely passing in options, your code is no different than:
let options = {
siteTitle: `Site title`,
// `this` is undefined since we are in strict mode
fromAuthorData: this.get('authorName'),
actions: {
showAuthor() {
var author = this.get('fromAuthorData');
console.log(`Author from controller: ${author}`);
},
}
};
export default Ember.Controller.extend(AuthorDatas, options);
Now to access properties that rely on this being the object holding it you will need a function that is run with the object as it's context that returns that value, enter computed properties.
Your code becomes:
// app/controllers/application.js
import Ember from 'ember';
import AuthorDatas from 'app-name/mixins/author-data';
const { computed } = Ember;
export default Ember.Controller.extend(AuthorDatas, {
siteTitle: `Site title`,
// We add `authorName` as the dependent key, should it change `fromAuthorData` will update
fromAuthorData: computed('authorName', function() {
// your author data stuff
let authorName = this.get('authorName');
// ...
return authorDetails;
}),
actions: {
showAuthor() {
var author = this.get('fromAuthorData');
console.log(`Author from controller: ${author}`);
},
},
});