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I have an NSAttributed string (coming from HTML) that I set for a UITextView. 

- (void)setHtml:(NSString *)html {

    NSData *htmlData = [html dataUsingEncoding:NSUTF8StringEncoding];

    // Create the HTML string
    NSDictionary *importParams = @{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};
    NSError *error = nil;
    self.htmlString = [[NSAttributedString alloc] initWithData:htmlData options:importParams documentAttributes:NULL error:&error];

    self.editorView.attributedText = self.htmlString;

}

I then let the user edit what they want, and I would like to then convert it out to HTML again, so I use:

- (NSString *)getHTML {
    NSDictionary *exportParams = @{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};
    NSData *htmlData = [self.editorView.attributedText dataFromRange:NSMakeRange(0, self.editorView.attributedText.length) documentAttributes:exportParams error:nil];
    return [[NSString alloc] initWithData:htmlData encoding:NSUTF8StringEncoding];
}

It does return HTML, but it isn't how I want it. Everything is given a class attribute, and the CSS it put at the top of the document. Things like images and links are not even included in the returned HTML and probably tons more issues.

Is there a better way to get HTML from an NSAttributedString? Or, is there a way I could parse the NSAttributedString and write my own HTML?

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3 Answers 3

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+100

May be you could look at that repository: https://github.com/IdeasOnCanvas/Ashton

there is 2 interesting class:

AshtonHTMLReader.h

 - (NSAttributedString *)attributedStringFromHTMLString:(NSString *)htmlString;

And the writer:

AshtonHTMLWriter.h

- (NSString *)HTMLStringFromAttributedString:(NSAttributedString *)input;

The html generated isn't very nice but if you try to display it in a uiwebview, it looks pretty good.

Simple idea for image: encode it with base64 and put it directly in a < img > tag with the right frame.

It's ugly but it works => I've used this process to create and edit some html file few month ago

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4 Comments

This is a cool idea, but checking the source shows it is quite limited in its parsing capabilities. Styling would be an issue.
Actually this is not ideal. But this project are used to retrieve fonts, colors, Italic / Bold style etc ...Another problem is that the use of base64 encoding for images directly into the html makes pages very long to load!
As an extension to the question: I am interested in a way to include images in HTML without using base64 encoding. Something like the microsoft's .chm format, if someone has any idea!
This project is great! I had an issue where I wanted to paste a UITextView's attributed text into an E-Mail message that the user could send to themselves. Using the method in the original question resulted in loss of much of the formatting (font type and size). With this project, you can just call mn_HTMLRepresentation which is a category method on NSAttributedString and pass that to an MFMailComposeViewController as the body, and voila, a beautifully formatted E-Mail that looks exactly as it did in the app's textview.
9

This is a complex issue, and I will start with a shorter answer. You may ask me questions in the comments, and I will expand on the answer as needed.

We also tried to go the attributed string route, but found it not suited for full HTML editing. Many elements are just not supported, either because the converter is not fully developed, or these elements were deemed outside of scope by Apple. Parsing the attributed string is not good enough, because the attributed string has already lost most of the richness of the HTML by the time you attempt to recreate it.

Instead, we use a webview, load the document normally, and enable contentEditable on the body element. What this does is allow editing of the document in its fullest, limited only by WebKit. At the end, to retrieve the HTML back, we disable contentEditable and take the document.outerHTML to get an entire HTML as it was before, with changes made by the user.

Don't take the decision to implement this method lightly. It is a somewhat complex solution, but certainly possible. A webview is not as nice as a textview, but it can be, given enough massage.

I will expand on this answer as needed.

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11 Comments

Thanks for the response, but we are specifically leaving the UIWebView implementation as it has some serious issues with speed/UIScrollViews. I've been able to get everything working except Lists.
@JesseNaugher I have extensive knowledge in fixing webview bugs. If you have specific questions, you can ask questions here or contact me directly. Anyway you look at it, webview is the most robust method for complex editing, unless you wish to enter the world of CoreText (aka the Apple Pages implementation).
This is the route I ended up going too. One issue I still have is being able to return valid XHTML. Did you fine a solution to this?
@NicHubbard While I have not tried, wouldn't giving an XHTML input work? I think edited HTML would preserve the strictness of XHTML just fine.
@LeoNatan Yes, it does. But, since you have to add a xmlns namespace, we found that when we grab the innerHTML that it adds that attribute to all block elements. So we were not sure how to get around that strange issue.
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I also had to convert a NSAtttributedString to HTML in one of my projects. The code for doing this is as follows

//self.attributed String is the attributedString 
NSDictionary *documentAttributes = @{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};
NSData *htmlData = [self.attributedString dataFromRange:NSMakeRange(0, self.attributedString.length) documentAttributes:documentAttributes error:NULL];
NSString *htmlString = [[NSString alloc] initWithData:htmlData encoding:NSUTF8StringEncoding];
NSLog(@"%@", htmlString);
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2 Comments

The limitation with this approach as already stated in the question is that it skips the img tag. I tested it out and found the img tag is skipped in 9.0 but works fine with iOS 10
Ohk I am glad it works for iOS 10. Sorry it doesn't work for iOS 9

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