Invalid property value: API create Mutation Sanity.io Reference is string - how to define as reference? - properties

Question

i am building a ecommerce site.
I have trouble adding orderItems to the Array in the Order-Document.
As you can see i am trying to reference the customer-Document and Product-Dokument in my orderItem. i am Posting in an array of objects that looks like:
[
{
productId: '5b79b3f8-6ef8-4c6d-bd85-5dcb14fb836d',
kundenId: 'c3777230-74cd-411b-a455-7fa905c90957',
quant: 1,
name: 'Position 1'
}
]
Can someone help me how i get sanity to understand the strings as _ref ?
My schemas are as follows:
export default {
title: 'Order Item',
name: 'orderItem',
type: 'object',
fields: [
{
title: 'Name',
name: 'name',
type: 'string',
},
{
name: 'kundenId',
title: 'Customer',
type: 'reference',
to: [{ type: 'customer' }],
options: {
disableNew: true,
},
},
{
name: 'productId',
title: 'Product',
type: 'reference',
to: [{ type: 'product' }],
options: {
disableNew: true,
},
},
{
title: 'Quantity',
name: 'quant',
type: 'number',
},
{
title: 'Price',
name: 'price',
type: 'number',
},
],
};
and:
export default {
name: 'order',
title: 'Order',
type: 'document',
fields: [
{
name: 'user',
title: 'User',
type: 'reference',
to: [{ type: 'user' }],
options: {
disableNew: true,
},
},
{
name: 'userName',
title: 'User Name',
type: 'string',
},
{
title: 'Order Items',
name: 'orderItems',
type: 'array',
of: [
{
title: 'Order Item',
type: 'orderItem',
},
],
},
{
title: 'CreatedAt',
name: 'createdAt',
type: 'datetime',
},
],
};

Answer 1

so i solved this by using JSON.parse like so:
productId: JSON.parse(`{"_ref":"${artikel._id}"}`),
Good luck to everyone with the same issue.