type 'String' is not a subtype of type 'int' of 'index' generally faced when you try to access a value from a map or list where the key or index is expected to be of type int, but you're providing a String (or vice versa). In your code, the problem is likely with how the API response data is being parsed in the fetchSertifikasi method.

Possible issue can be:

In fetchSertifikasi, you're returning response.data['data'], assuming it contains a list of dynamic objects (like maps). However, in your main project, the data field might not have the expected structure, or some fields (e.g., id_sertifikasi) might not have the correct data type (e.g., being a String instead of an int).

Debuging steps

Step 1: Log the response from the API to see its exact structure and confirm data types.

Step 2: Ensure Consistent Data Types If the API is returning id_sertifikasi as a String instead of int, you should modify how you handle this data.

Step 3: Check JSON Parsing If you expect specific data types from the API, use a model class to parse and validate the JSON