objective c - Saving custom attributes in NSAttributedString

Question

I need to add a custom attribute to the selected text in an NSTextView. So I can do that by getting the attributed string for the selection, adding a custom attribute to it, and then replacing the selection with my new attributed string.

So now I get the text view's attributed string as NSData and write it to a file. Later when I open that file and restore it to the text view my custom attributes are gone! After working out the entire scheme for my custom attribute I find that custom attributes are not saved for you. Look at the IMPORTANT note here: http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Conceptual/AttributedStrings/Tasks/RTFAndAttrStrings.html

So I have no idea how to save and restore my documents with this custom attribute. Any help?

Answer 1

The normal way of saving an NSAttributedString is to use RTF, and RTF data is what the -dataFromRange:documentAttributes:error: method of NSAttributedString generates.

However, the RTF format has no support for custom attributes. Instead, you should use the NSCoding protocol to archive your attributed string, which will preserve the custom attributes:

//asssume attributedString is your NSAttributedString
//encode the string as NSData
NSData* stringData = [NSKeyedArchiver archivedDataWithRootObject:attributedString];
[stringData writeToFile:pathToFile atomically:YES];

//read the data back in and decode the string
NSData* newStringData = [NSData dataWithContentsOfFile:pathToFile];
NSAttributedString* newString = [NSKeyedUnarchiver unarchiveObjectWithData:newStringData];