How to Successfully Retrieve Data from Multiple Forms in Flask Using Ajax: A Concise Guide

Learn how to send multiple forms' data to a Flask server using Ajax. Discover the correct way to gather form inputs and make effective requests with easy-to-follow steps.
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How to Successfully Retrieve Data from Multiple Forms in Flask Using Ajax: A Concise Guide

When working with web applications, it's common to collect user input through forms. In many scenarios, developers may need to send data from multiple forms to a web server, such as when using Flask as a back end. However, a common issue arises when trying to send multiple form data together with Ajax. This guide addresses the challenge of retrieving data from multiple forms in Flask and offers a straightforward solution.

The Problem: Sending Multiple Forms to Flask

In the provided example, the user's intention is to send data from two different forms (form1 and form2) to a Flask server. However, despite successful uploading of files, the server struggles to retrieve the inputs from the second form. The challenge lies in how the data is structured and sent through Ajax. Below are key points to help us understand the issue at hand:

Data from form2 isn't accessible: The input values filled in the second form (form2) aren’t being passed correctly, leaving the server blind to these inputs.

The Solution: Properly Structure Form Data

To handle multiple forms correctly when sending data to Flask, the FormData object may not be nested (i.e., you cannot append one FormData object into another). Instead, you must collect all fields from both forms and populate a single FormData object. Below are step-by-step instructions to achieve this.

Step 1: Modify the JavaScript to Capture All Form Fields

Revise the Ajax call to manually append fields from both forms to a single FormData object. Here's how you can do this:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Update the Ajax Function

Make sure that you send the consolidated FormData object in your Ajax call. Here is a refreshed version of your send_request_to_flask function:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Execute the Function on Event Trigger

Ensure the function fires correctly when relevant events occur, such as when the user interacts with the file input or submits the form:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the outlined steps, you’ll be able to successfully send data from multiple forms to a Flask back end using Ajax. Rather than attempting to append one FormData object to another, collect all necessary fields from both forms into a single FormData object. This method ensures that all inputs are sent together, making it easy for your Flask server to process them.

By taking these measures, you not only solve the issue of retrieving form data, but you also gain better control over the data being sent to your server. Happy coding!