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PONSInvocation for Dummies?
 

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    <p>How exactly does <code>NSInvocation</code> work? Is there a good introduction?</p> <p>I’m specifically having issues understanding how the following code (from <em>Cocoa Programming for Mac OS X, 3rd Edition</em>) works, but then also be able to apply the concepts independently of the tutorial sample. The code:</p> <pre><code>- (void)insertObject:(Person *)p inEmployeesAtIndex:(int)index { NSLog(@"adding %@ to %@", p, employees); // Add inverse of this operation to undo stack NSUndoManager *undo = [self undoManager]; [[undo prepareWithInvocationTarget:self] removeObjectFromEmployeesAtIndex:index]; if (![undo isUndoing]) [undo setActionName:@"Insert Person"]; // Finally, add person to the array [employees insertObject:p atIndex:index]; } - (void)removeObjectFromEmployeesAtIndex:(int)index { Person *p = [employees objectAtIndex:index]; NSLog(@"removing %@ from %@", p, employees); // Add inverse of this operation to undo stack NSUndoManager *undo = [self undoManager]; [[undo prepareWithInvocationTarget:self] insertObject:p inEmployeesAtIndex:index]; if (![undo isUndoing]) [undo setActionName:@"Delete Person"]; // Finally, remove person from array [employees removeObjectAtIndex:index]; } </code></pre> <p>I get what it’s trying to do. (BTW, <code>employees</code> is an <code>NSArray</code> of a custom <code>Person</code> class.)</p> <p>Being a .NET guy, I try to associate unfamiliar Obj-C and Cocoa concepts to roughly analogous .NET concepts. Is this similar to .NET’s delegate concept, but untyped? </p> <p>This isn’t 100% clear from the book, so I’m looking for something supplemental from real Cocoa/Obj-C experts, again with the goal that I understand the fundamental concept beneath the simple(-ish) example. I'm really looking to be able to independently apply the knowledge -- up until chapter 9, I was having no difficulty doing that. But now ... </p> <p>Thanks in advance!</p>
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