Mryntu

There has been similar issues posted without an answer unfortunately but I am posting two ways in the API to set a category on a product both of which give different errors.

The first is using the categories repository (catalogCategoryLinkRepositoryV1)

example
In body POST

 
 "productLink" :
 
 "sku" : "TEST_SKU5", 
 "position" : 0, 
 "categoryId" : "8",
 "extensionAttributes": 

 
 

Example Response : This is the same response regardless of what category or product.

 "message": "Could not save product "%1" with position %2 to category %3",
 "parameters": [
 "144",
 0,
 "8"
 ]

The second is setting it under custom_attribute using the product repository in either new or update calls. Both give the same result.

When setting the custom_attribute like below regardless of what sku and category I get an error. If I leave out "category_ids" it works fine but defeats the purpose of using the API to manage product import and updates.

'custom_attributes' => array(
 array( 'attribute_code' => 'category_ids', 'value' => ["8"] ),
 array( 'attribute_code' => 'description', 'value' => 'Simple Description' ),
 array( 'attribute_code' => 'short_description', 'value' => 'Simple Short Description' ),
 )

Error being the following, which is the only error I get regardless of what combination of sku and category even if the sku is not made yet and I am creating a new product..

""message":"URL key for specified store already exists.""

You have to check below code for set product in category with position,

 <?php 
 $url="http://127.0.0.1/magento2.1/"; //your custom site url...
 $token_url=$url."rest/V1/integration/admin/token";

 //Below 9 is category id....
 $product_url=$url. "rest/V1/categories/9/products"; 
 $username="admin";
 $password="admin123";
 //Authentication rest API magento2, get access token
 $ch = curl_init();
 $data = array("username" => $username, "password" => $password);
 $data_string = json_encode($data);

 $ch = curl_init($token_url);
 curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
 curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 curl_setopt($ch, CURLOPT_HTTPHEADER, array(
 'Content-Type: application/json',
 'Content-Length: ' . strlen($data_string))
 );
 $token = curl_exec($ch);
 $adminToken= json_decode($token);

 //9 is category id...
 $sampleProductData = array(
 "sku" => "24-MB01",
 "position" => 5,
 "category_id" => "9",
 "extension_attributes" => array()
 );
 $categoryData = json_encode(array('productLink' => $sampleProductData));

 $setHaders = array('Content-Type:application/json','Authorization:Bearer '.$adminToken);
 $ch = curl_init();
 curl_setopt($ch,CURLOPT_URL, $product_url);
 curl_setopt($ch,CURLOPT_POSTFIELDS, $categoryData);
 curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
 curl_setopt($ch, CURLOPT_HTTPHEADER, $setHaders);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 $response = curl_exec($ch);
 curl_close($ch);