# Save instance with natural compound id

**URL:** <https://forums.bitovi.com/t/save-instance-with-natural-compound-id/654>\
**Category:** CanJS\
**Created:** [June 2, 2017, 4:47pm UTC](https://forums.bitovi.com/t/save-instance-with-natural-compound-id/654 "2017-06-02T16:47:04Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Gregorio\_Godoy](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@Gregorio\_Godoy](https://forums.bitovi.com/u/Gregorio_Godoy)\
**Post date:** [June 2, 2017, 4:47pm UTC](https://forums.bitovi.com/t/save-instance-with-natural-compound-id/654/1 "2017-06-02T16:47:04Z")

</div>

Hi,

I have the following model:

```auto
import DefineMap from 'can-define/map/';
import DefineList from 'can-define/list/';
import set from 'can-set';
import superMap from 'can-connect/can/super-map/';
import loader from '@loader';

const QuickbriefDetail = DefineMap.extend({
	seal: false
}, {
	quickbrief_number: 'number',
	product_id: 'number'
});

const algebra = new set.Algebra(
	set.props.id('quickbrief_number'),
	set.props.id('product_id')
);

QuickbriefDetail.List = DefineList.extend({
	'#': QuickbriefDetail
});

QuickbriefDetail.Connection = superMap({

	url: loader.serviceBaseURL + '/quickbrief_detail',  
	Map: QuickbriefDetail,
	List: QuickbriefDetail.List,
	name: 'quickbrief_detail',
	algebra
});

export default QuickbriefDetail;

```

The quickbrief\_detail table has a composite primary key or compound id: quickbrief\_number and product\_id. Please note the models algebra. I can see in the inspector that all retrieved instances have an id {quickbrief\_number}@|@{product\_id}. So, algebra is working as expected, its assuming the compound id, GREAT!

But, when i need to persist a **new** instance calling save(), the connection’s updateData function is called. But what i want is that the createData function is called. I want to POST to the API, not PUT.

```auto
var modelInstance = new QuickbriefDetail({
	quickbrief_number: 1,
	product_id: 5,
	prize: 100,
	description: 'Some description'
});

modelInstance.save();

```

I understand that save(), evaluates if the instance has the id property defined. In this case, the id is defined by the algebra and both properties are set with a value (quickbrief\_number, product\_id). The values are setted by the app, not generated by the API like a sequence.

What is the best or less hackish approach to resolve this scenario? I was considering add a property called \_new (boolean) acting as a flag and overwrite the save method. When the instance is retrieved from database the property \_new will not exist, but when the instance is no yet persisted i would add the \_new prop with the value true. And in the save() function i would evaluate this flag.

But im sure someone else had the same scenario and is somehow resolved. I just cant figure it out how.

Any comments and help is really appreciated! THANKS

---

<div class="post-metadata">

**Author:** ![pmgmendes](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.bitovi.com/pmgmendes/32/248_2.png) [@pmgmendes](https://forums.bitovi.com/u/pmgmendes)\
**Post date:** [June 19, 2017, 10:27pm UTC](https://forums.bitovi.com/t/save-instance-with-natural-compound-id/654/2 "2017-06-19T22:27:09Z")

</div>

@Gregorio_Godoy, the following might work:

- Add a new boolean prop “\_ new” to your type.
- Provide your own “id” method to the type’s connection (see docs can-connect/base/base.js#id). Your id’s implementation returns “undefined” when instance.\_new is true. This way constructor.js#save will fall into the createData flow instead of updateData.
- To set instance.\_new to false provide a custom “hydrateInstance” method in a custom behavior that still calls the baseConnection#hydrateInstance (because you’re using the superMap I’m not sure where your custom method should be declared in order to be picked up…).