Azure pre-triggers

Question

My goal is when I create a new item, the trigger sets the age to 18 years old.

this is my trigger function :

function trigger(item) {
    // Check if the document has an "age" field
    console.log("started triggering");
    if (item && item.age !== undefined) {
        // Update the "age" field to 18
        item.age = 18;
        console.log("done");
    }
    // Continue with the operation (insert)
    return item;
}

When I create new item, the age doesn't change input :

{
      "id": "86",
      "name": "dhia",
      "age": 11
}

output :

{
    "id": "86",
    "name": "dhia",
    "age": 11
}

My goal is when I create a new item, the trigger sets the age to 18 years old.

I tried to set the name, the age, even a small change to see the trigger working because I'm learning and this is my first pre-trigger ever.

Answer 1

My goal is when I create a new item, the trigger sets the age to 18 years old.

As Gaurav Mantri explained in this SO thread, the triggers are not run automatically whenever a document is inserted. What you would need to do is specify the trigger that you want to run when you're creating the document.

Below are the steps I followed:

• An object is created by CosmosClient utilizing a connection string containing an Azure Cosmos DB account's login data.

• The GetContainer function is used to get a reference to a particular container within the Cosmos DB account.

• An anonymous type having the properties id, name, and age is used to define an object.

• It generates an ItemRequestOptions object and sets the PreTriggers property of that object to a list with the pre-trigger name updateAge. This pre-trigger will be executed before creating the item.

• CreateItemAsync method on the container is used to create the item asynchronously.

• The item is the new document, null shows that the code doesn't specify a particular partition key, and requestOptions has the pre-trigger data.

Pre-Trigger:

function updateAge() {
  var context = getContext();
  var request = context.getRequest();
  var itemToCreate = request.getBody();
 
  itemToCreate.age = 18;

  request.setBody(itemToCreate);
}

• The request context and the object to be created are retrieved by updateAge().

• It modifies the age property of the item to set it to 18.

• Uses request.setBody(itemToCreate) to update the item's content with the modified age value.

Below Is the code I tried with:

public async Task CreateItemAsync()
{
    try
    {
        var client = new CosmosClient("*****");
        var container = client.GetContainer("newData", "newCont");

        var item = new
        {
            id = "3",
            name = "Pavan Balaji",
            age = 30
        };

        var requestOptions = new ItemRequestOptions
        {
            PreTriggers = new List<string> { "updateAge" }
        };

        var response = await container.CreateItemAsync(item, null, requestOptions);

        Console.WriteLine($"Request Charge: {response.RequestCharge}");
    }
    catch (CosmosException ex)
    {
        Console.WriteLine($"Cosmos DB Exception: {ex.Message}");
    }
}

static async Task Main(string[] args)
{
    ClassName Instance = new ClassName();
    await Instance.CreateItemAsync();
}

Output:

{
    "id": "3",
    "name": "Pavan Balaji",
    "age": 18
}