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    <p>Objective-C methods are designed to be self documenting, and they borrow from the rich tradition of Smalltalk.</p> <p>I'll try to explain what you have here, <code>-(NSInteger) pickerView:(UIPickerView*)pickerView numberOfRowsInComponent:(NSInteger)component</code>.</p> <ul> <li><p><code>- (NSInteger)</code><br> This first portion indicates that this is an Objective C <strong>instance</strong> method that returns a NSInteger object. the <code>-</code> (dash) indicates that this is an <strong>instance</strong> method, where a <code>+</code> would indicate that this is a <strong>class</strong> method. The first value in parenthesis is the return type of the method. </p></li> <li><p><code>pickerView:</code><br> This portion is a part of the <strong>message name</strong>. The <strong>full message name</strong> in this case is <code>pickerView:numberOfRowsInComponent:</code>. The Objective-C runtime takes this method information and sends it to the indicated receiver. In pure C, this would look like<br> <code>NSInteger pickerView(UIPickerView* pickerView, NSInteger component)</code>. However, since this is Objective-C, additional information is packed into the message name. </p></li> <li><p><code>(UIPickerView*)pickerView</code><br> This portion is part of the <strong>input</strong>. The input here is of type <code>UIPickerView*</code> and has a local variable name of pickerView. </p></li> <li><p><code>numberOfRowsInComponent:</code><br> This portion is the second part of the <strong>message name</strong>. As you can see here, message names are split up to help indicate what information you are passing to the receiver. Thus, if I were to message an object myObject with the variables foo and bar, I would type:<br> <code>[myObject pickerView:foo numberOfRowsInComponent:bar];</code><br> as opposed to C++ style:<br> <code>myObject.pickerView(foo, bar);</code>.</p></li> <li><p><code>(NSInteger)component</code><br> This is the last portion of the <strong>input</strong>. the input here is of type <code>NSInteger</code> and has a local variable name of component.</p></li> </ul>
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    1. CO+1 for a great answer. I would suggest changing "factory" to "class" in your first point, since the "+" officially indicates a class method. It just so happens that many "+" methods are factory methods, but that isn't the proper definition.
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    2. COThanks! One additional question: If you were to message an object myObject with the variables foo and bar like you showed: [myObject pickerView:foo numberOfRowsInComponent:bar]; Does pickerView refer to the method name or parameter?
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    3. CONeither. It is good style for it to refer to both the method name AND parameter, but the full method name is actually pickerView:numberOfRowsInComponent:. If you were to try to invoke pickerView:, you would recieve a runtime error, as the method would not exist.
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