Question

I’ve come across what I think is an interesting bug in iOS 5.0 (this code works perfectly in 5.1). After ages of narrowing it down using lots of Console.Write()’s, I narrowed the crash to:

nsUrl.ToString();

This is either in the MonoTouch library or iOS.

Anybody else come across this? It’s annoying, as we obviously want to support the minimum iOS version possible.

Answer 1

In MonoTouch the default ToString implementation, for NSObject subclasses, is to call the description selector.

In some cases (and yes it varies with iOS versions) calling description can fail (or even crash the process). That generally occurs when the native object is a bad state (e.g. mis-initialized, invalid value…).

MonoTouch tries to handle such cases (when possible and known) by using a different ToString implementation (e.g. with extra checks or by falling back to the default ToString, which returns the type name).

Note: If you find such behaviour please report them in bug reports and we’ll see if they can be handled differently.