What is the difference between NSURLRequest's mainDocumentURL and URL properties?

Question

I've built a web browser for iOS and I'm trying to pull the URL to display in an address bar.
I look at the NSURLRequest in the webView:shouldStartLoadWithRequest:navigationType: and the webViewDidFinishLoad: UIWebView delegate methods.

Should I use the URL or the mainDocumentURL property of the NSURLRequest for that purpose, and what is the difference?

Wil Shipley · Answer 1 · 2014-01-28T21:15:49.227

3

You want to use URL.

mainDocumentURL would be used when loading sub-parts of a page (like images, scripts, whatever) to tell the system which cookies it can safely use when loading those sub-parts. It’s nothing you’d want to display, and is documented to be unused in the current version of the framework anyhow.

/*!
    @method mainDocumentURL
    @abstract The main document URL associated with this load.
    @discussion This URL is used for the cookie "same domain as main
    document" policy. There may also be other future uses.
    See setMainDocumentURL:
    NOTE: In the current implementation, this value is unused by the
    framework. A fully functional version of this method will be available 
    in the future. 
    @result The main document URL.
*/

edited Jan 28 '14 at 21:15

answered Jan 28 '14 at 19:47

Wil Shipley

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Where does the documentation say that it is unused? It looks like in the tests I've run that URL is not set and mainDocumentURL is set in the webView:shouldStartLoadWithRequest:navigationType: delegate method in some instances. – Austin Jan 28 '14 at 19:54
I’m not clear how an NSURLRequest would load anything if it doesn’t have a URL to load, but I’m not an expert in this realm. – Wil Shipley Jan 28 '14 at 21:16
I would advise using mainDocumentURL instead of URL. As a matter of fact URL can refer to a sub-part of the site the UIWebView is currently displaying. – Joss Sep 17 '14 at 09:53

score 1 · Answer 2 · edited Jun 20 '20 at 09:12

The documentation is not very clear, but it appears that mainDocumentURL used for cookie policy internals.

From NSHTTPCookieStorage Class Reference > setCookies:forURL:mainDocumentURL:

mainDocumentURL

The URL of the main HTML document for the top-level frame, if known. Can be nil. This URL is used to determine if the cookie should be accepted if the cookie accept policy is NSHTTPCookieAcceptPolicyOnlyFromMainDocumentDomain.

If it's possible that the URL you are using is a sub-frame or some media type embedded in an HTML document, then you may wish to know what the mainDocumentURL is; otherwise, just use URL.

What is the difference between NSURLRequest's mainDocumentURL and URL properties?

2 Answers2