Objective C override %@ for custom objects

I'd like to override the default print function in NSLog for custom objects;

For example:

MyObject *myObject = [[MyObject alloc] init];
NSLog(@"This is my object: %@", myObjcet);

Will print out:

This is my object: <MyObject: 0x4324234>

Is there a function I override in MyObject to print out a prettier description?

Cheers! Nick.