Adding metadata to an image in an iOS application

Question

I am creating an application to take a picture and save the image in the camera frame, but at the same time adding a data line to the image metadata, and this line will basically be a combination of user input in several text fields. So I take the image using the iphone camera that UIImagePicker is accessing. Now I want to save this and edit the metadata before saving. I was looking for a solution, but could not find a suitable one for a quick one.