Peter Duniho wrote:
In C#:
void setColor(NSColor color)
{
undoManager.prepareWithInvocationTarget(this).setColor(mColor);
mColor = color;
}
Your point being? If you think your example is useful in presenting
your claim, you'll need to be a lot more specific.
[...]
Well, I'm still waiting for someone to show me how that flexibility
is used. You are certainly doing a great job of stating the same
party line I've heard countless times already. But you're also
failing to provide a compelling example of how this flexibility
comes into play in the real world. Again, this is not only typical,
it's characteristic of _every_ single time I've heard the party line
stated.
You've translated the Objective-C syntax into C# syntax, but the point
of the question is to think about what prepareWithInvocationTarget()
does. How would you write that method in C#?
In Objective-C, after you call -prepareWithInvocationTarget: on an
NSUndoManager, it then accepts _any_ message call of any kind. It is
completely and totally dynamic. It accepts messages from your
application which weren't defined and didn't exist when the
NSUndoManager class was compiled. The undo manager accepts the
message, saves the target and method invocation with an arbitrary
number of arguments and is able to re-invoke it later on the original
target when the user asks you to Undo.
This is an example of what a dynamic message dispatch mechanism can do
for you. How would you implement that in a direct invocation or v-
table environment? Of course Undo is still doable in Java or C#: these
are all turing equivalent languages, but how much code would it take
and how complicated would it be for the programmer using the undo
management library to define this-is-something-to-undo?
Hope this helps,
- Greg
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