Ember: Setting a component object value within a promise - ember.js

Question

I have component with a couple of properties, using a promise in the willRender hook to try and create a (pagination) object:
export default Ember.Component.extend({
pagination:null,
testing:null, // to check if this.set is ok within the promise!
willRender() {
let page = {};
let model = this.get('data');
model.get('products').then(relatedItems => {
let maxRecords = relatedItems.get('length');
relatedItems.forEach(function(item,index) {
if (item.get('slug') === itemModel.get('id')) {
if (index === 0) {
page.Prev = null;
page.Next = relatedItems.objectAt(index+1).get('slug');
}
else if (index+1 === maxRecords) {
page.Prev = relatedItems.objectAt(index-1).get('slug');
page.Next = null;
}
else {
page.Prev = relatedItems.objectAt(index-1).get('slug');
page.Next = relatedItems.objectAt(index+1).get('slug');
}
}
});
this.set('testing','hello world');
console.log(this.get('testing')); // hello world
this.set('pagination',page);
console.log(this.get('pagination')); // Object {Prev: "product-1", Next: "product-2"}
},reject => {
console.log('error '+reject);
});
}
})
In my template
{{testing}} // prints hello world
However, if I try and access {{pagination}} eg {{log pagination}}, the browser crashes with a loop printing out the object to the console.
I don't know where I'm going wrong here - any help much appreciated!

Answer 1

It's likely you are triggering the template to rerender causing willRender to fire over and over which causes an infinite loop in your code.
willRender is a non-standard place to do this code, init would be more standard since it only fires on initialization of the component. Even better would be to use
myInit: Ember.on('init', function(){
....
})`
instead of overriding willRender on the object.

Answer 2

try to check whether Object is present at specific position. i think its going undefined during iteration of for loop. try to ensure that ObjectAt is not returning undefined or null value during running of for loop.
relatedItems.forEach(function(item,index) {
if (item.get('slug') === itemModel.get('id')) {
if (index === 0) {
page.Prev = null;
if(relatedItems.objectAt(index+1) ! = undefined) {
page.Next = relatedItems.objectAt(index+1).get('slug');
}else{
page.Next == null;
}
}
else if (index+1 === maxRecords) {
if(relatedItems.objectAt(index-1) ! = undefined) {
page.Prev = relatedItems.objectAt(index-1).get('slug');
}else{
page.Prev = null;
}
page.Next = null;
}
else {
if(relatedItems.objectAt(index-1) ! = undefined) {
page.Prev = relatedItems.objectAt(index-1).get('slug');
}else{
page.Prev = null;
}
if(relatedItems.objectAt(index+1) ! = undefined) {
page.Next = relatedItems.objectAt(index+1).get('slug');
}else{
page.Next = null;
}
}
}
Please ensure that Object at is returning object.

Answer 3

There seems to be a few problems here, would be interested to know what your console errors are.
You don't seem to have defined itemModel so don't know how you're referencing that.
Also you can't access this from within a .then. You need to do something like this to set a component variable.
var _this = this;
promise().then(function(results) {
_this.set('testing', 'hello world');
});

Answer 4

you are not using , after testing:null
there should be , after testing property like that
pagination:null,
testing:null, // i use ',' after testing: null property

Answer 5

try to use your pagination code under init hook rather than willrender hook
init() {
//you code
},