# init(contentsOf:options:) Initializes and returns an `NSXMLDTD` object created from the DTD declarations in a URL-referenced source. ``` convenience init(contentsOf url: URL, options mask: XMLNode.Options = []) throws ``` ## Parameters `url` An [`NSURL`](/documentation/Foundation/NSURL) object identifying a URL source. `mask` A bit mask specifying input options; bit-OR multiple options. The current valid options are `NSXMLNodePreserveWhitespace` and `NSXMLNodePreserveEntities`; these constants are described in the “Constants” section of the [`XMLNode`](/documentation/Foundation/XMLNode) reference. ## Return Value An initialized `NSXMLDTD` object or `nil` if initialization fails because of parsing errors or other reasons. ## Discussion You use this method to create a stand-alone DTD which you can thereafter query and use for validation. You can associate the DTD created through this message with a document by setting the [`dtd`](/documentation/Foundation/XMLDocument/dtd) property on an [`XMLDocument`](/documentation/Foundation/XMLDocument) object. > Handling Errors in Swift: > In Swift, this method returns a nonoptional result and is marked with the `throws` keyword to indicate that it throws an error in cases of failure. > > You call this method in a `try` expression and handle any errors in the `catch` clauses of a `do` statement, as described in [Error Handling](https://docs.swift.org/swift-book/LanguageGuide/ErrorHandling.html) in [The Swift Programming Language](https://docs.swift.org/swift-book/) and `About Imported Cocoa Error Parameters`. ## See Also [`- validateAndReturnError:`](/documentation/Foundation/XMLDocument/validate()) Validates the document against the governing schema and returns whether the document conforms to the schema. [Tree-Based XML Programming Guide](https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/NSXML_Concepts/NSXML.html#//apple_ref/doc/uid/TP40001269) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)