class func availableMemory() -> size_t { return os_proc_available_memory() } Cannot find 'os_proc_available_memory' in scope Is there a version I can access from Swift?

memoryFootprint is quite confusing code but useful. Putting it in the debugger and studying info (at line return info.phys_footprint) I see it has a field limit_bytes_remaining Is this a useful guideline as to how much memory is available for allocation? I notice that when UIGraphicsBeginImageContextWithOptions(size,....) fails with a message "Cannot allocate X bytes" X is 16 x size.width x size.height I would like to know if UIGraphicsBeginImageContextWithOptions will fail before I call it and crash

This is ongoing. I simplified the code to: import UIKit func SaveImageAsPhoto(image:UIImage) { UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil) } and I get the same results. At best it works half the time.

Do I need to use a semephore to serialise the callback? If I call UIImageWriteToSavedPhotosAlbum twice without waiting for the callback to complete will the second call fail silently?