How do i convert NSAttributedString into HTML string?

Solution 1:

Use dataFromRange:documentAttributes: with the document type attribute (NSDocumentTypeDocumentAttribute) set to HTML (NSHTMLTextDocumentType):

NSAttributedString *s = ...;
NSDictionary *documentAttributes = @{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};    
NSData *htmlData = [s dataFromRange:NSMakeRange(0, s.length) documentAttributes:documentAttributes error:NULL];
NSString *htmlString = [[NSString alloc] initWithData:htmlData encoding:NSUTF8StringEncoding];

Solution 2:

This is a swift 4 conversion of @omz answer, hope is useful to anyone landing here

extension NSAttributedString {
    var attributedString2Html: String? {
        do {
            let htmlData = try self.data(from: NSRange(location: 0, length: self.length), documentAttributes:[.documentType: NSAttributedString.DocumentType.html]);
            return String.init(data: htmlData, encoding: String.Encoding.utf8)
        } catch {
            print("error:", error)
            return nil
        }
    }
}