Ember: Setting a component object value within a promose

I have component with a couple of properties, using a promise in the willRender hook to try and create (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 => {

          relatedItems.forEach(function(item,index) {
              // set up the page object here, omitted for brevity
          });
          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

 // prints hello world

However, if I try and access eg , 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!