How can I add a custom attribute in REST API?

[springimport]

Question 1:

I'm trying place an order using Magento 2 API. I have a custom attribute that I want to submit along with this.
I tried submitting the custom attribute.

{
  "paymentMethod": {
    "poNumber": "1234567",
    "method": "purchaseorder"
  },
  "billingAddress": {
    "firstname": "Tom",
    "lastname": "Sawyer",
    "region": {
        "region_code": "NY",
        "region": "New York",
        "region_id": 43
    },
    "region_id": 43,
    "country_id": "US",
    "street": [
        "Main St"
    ],
    "telephone": "64868564631",
    "postcode": "11011",
    "city": "New York"
  },



  "order_date": "2003-01-16 23:12:01" // my custom attribute
}

But it comes back with the error below:

Property \"OrderDate\" does not have corresponding setter in class \"Magento\\Quote\\Api\\Data\\PaymentInterface\

Question 2:

I'm trying to add a custom field to the following:

1. [GET] /V1/orders/{id}
2. [GET] /V1/orders

How can I extend Magento\Sales\Api\Data\OrderInterface?

[SerhiyShkolyarenko]

@springimport to declare custom attribute to interface please look through http://devdocs.magento.com/guides/v2.0/extension-dev-guide/attributes.html
You can find examples at code/Magento/GiftCardAccount/etc/extension_attributes.xml and code/Magento/Quote/etc/extension_attributes.xml

For examples of payload please refer to http://devdocs.magento.com/swagger/index.html =>
salesOrderRepositoryV1 => POST /V1/orders

[springimport]

You can find examples at code/Magento/GiftCardAccount/etc/extension_attributes.xml and code/Magento/Quote/etc/extension_attributes.xml

I have Vendor\OrderAttributes\etc\extension_attributes.xml

<?xml version="1.0"?> 
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Sales\Api\Data\OrderInterface">
        <attribute code="order_date" type="string"/>
    </extension_attributes>
</config>

For examples of payload please refer to http://devdocs.magento.com/swagger/index.html =>
salesOrderRepositoryV1 => POST /V1/orders

{
    "message": "Request does not match any route.",
    "trace": null
}

[springimport]

{
    "message": "Request does not match any route.",
    "trace": null
}

I solved this problem upgraded magento to 2.1.0.

[springimport]

I still don't understand how to add attributes. In your link "orders" do not participate in EAV attributes.

I guess I need to use an interface, but how?

[SerhiyShkolyarenko]

@springimport, I created a module with etc/extension_attributes.xml file equivalent to yours and passed checkout. \Magento\Sales\Api\Data\OrderExtensionInterface was autogenerated in var/generation/Magento/Sales/Api/Data/OrderExtensionInterface.php
It has getOrderDate() and setOrderDate() methods. Don't you have the same?

[SerhiyShkolyarenko]

To generate this extension interface you may also use ./bin/magento setup:di:compile

[springimport]

@SerhiyShkolyarenko Придется объяснить так.

Этого файла в системе нет.
\Magento\Sales\Api\Data\OrderExtensionInterface

Этот есть, да, с нужными методами getOrderDate() and setOrderDate().
var/generation/Magento/Sales/Api/Data/OrderExtensionInterface.php

Я уже понял что API требует интерфейс для понимания какие поля нужно возвращать, в данном случае он получает \Magento\Sales\Api\Data\OrderInterface который по определению не имеет моих методов и константы const ORDER_DATE = 'order date'; Поэтому в ответе не будет моего атрибута.

Как временное решение я пофиксил @return в паре классов на мой интерфейс, это помогло.

Так же я так и не понял как OrderExtensionInterface может повлиять на ситуацию.

[SerhiyShkolyarenko]

@springimport Sorry we can use here english only as an international language.
\Magento\Sales\Api\Data\OrderExtensionInterface is autogenerated interface, so corresponding class is located at var/generation directory.
Full documentation is here: http://devdocs.magento.com/guides/v2.0/extension-dev-guide/attributes.html
As an example please investigate code/Magento/GiftMessage/etc/extension_attributes.xml and code/Magento/GiftMessage/etc/di.xml. In the first file gift_message option is added to Magento\Sales\Api\OrderRepositoryInterface and in the second two plugins are added to this interface for gift_message option processing on save and load.