Daniel Walker wrote:
On 4/23/06, Peter Dimov <pdimov@mmltd.net> wrote:
Daniel Walker wrote:
On 4/23/06, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
Ok, why is that exception better than the one I generate if I don't meet the tag I expect, of if the contents of a tag is not of the type I expect?
Well, you don't have to write C++ code to check if the tag/content is what you expect. You declare the acceptable content (tags, attribute/values, branch structures/sub-trees, etc) for your config file in a schema, and the parser determines whether or not the XML file conforms to the format declared in the schema.
I wouldn't omit the checks in the code, even when using a validating parser. When the schema and the program logic disagree, the program logic "wins". Or crashes. Either way, the schema loses. :-)
Good point about crashes. It is still possible to write programs that crash even when using a schema. There is no silver bullet. Whether or not you want to double check the parser/scheme is the same sort of decision as whether or not you define NDEBUG in a released/deployed system. Sure, the asserts are still useful, but do you really need the extra check? The answer probably depends on the specific circumstances and is somewhat a matter of taste. I think the more common case is that you forget to manually check a constraint on the XML in your code, in which case you would be glad if you had a validating parser.
At least for my code, a crash is not acceptable compared to a nice popup message: "Error in xml-file: foo"; -Thorsten