override description or stringValue in cocoa?

I want to have an descriptive string for an object in Cocoa. I'm thinking about overr开发者_如何学编程iding either the description method or the stringValue method. Which is preferable and why? The only guideline I could find was in here stating

You are discouraged from overriding description.

Is this indeed what you would suggest? Any other preferred overrride point?

I personally override description in virtually all subclasses I create. I guess, like Tom Duckering writes in his comment, that your quote only applies to Managed Objects.

- (NSString *)description
{
    return [NSString stringWithFormat:@"%@ <%p>", NSStringFromClass([self class]), self];
}

description is the way to go, that's what it's called to supply string representation of an object.

- (NSString*)description
{
    return [NSString stringWithFormat:@"%@, %@; %@", a, b, c];
}

I believe suggested by Hillegass' book as well.

To answer your question from the other direction, stringValue is something altogether different—it doesn't describe the receiver, it's a property of it. Your custom description may even include the stringValue, or an excerpt of it if it's long.

A key difference is that stringValue is often a mutable property (see, for example, that of NSControl), whereas description is always an immutable property, computed upon demand.

You can also override [NSObject debugDescription] which is called by the debugger. It's what is called when use "print to console" in the debugger. You can also call it directly in a NSLog.

By default in most classes debugDescription just calls description but you can make them return separate strings. It's a good place to load up the output with details.

Categories are a good place to park the method for both your custom classes and existing classes. This is especially useful because you can include the category in a debug build but exclude it in the release. If the category is not present, the code calls the default class method instead.

I have a debugging category for UIView that dumps out every attribute I could think of. If I hit a nasty bug I just include the category and then I can see everything about every view right in the debugger console.