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Things like TList are all very useful classes, and our code is made much simpler, easier to maintain, and more type-safe because of them. But using them merely makes us consumers of generics. If we want to truly take advantage of generics, we need to become producers of generic classes. It’s a big step to see the benefit of generic collections, but the truly big step is to start seeing opportunities for the use of generics in your own code. 7 A Contrived, Simple Example So in order to start thinking about generics with a producer’s mindset, consider the following code: type TOrderItem = class ID: integer; end; TOrder = class ID: integer; end; TCustomer = class ID: TGUID; end; Now this code is very simple – a set of classes that might represent a basic order entry system.

It’s quite straight forward. You simply declare a variable of the interface type you want to create, and then assign to it an instance of an object that implements that interface. '); end; Here are some things to note about the simple example above: • First, TPerson descends from TInterfacedObject, and therefore it meets the minimum requirements for implementing an interface – that is, _AddRef, _Release, and QueryInterface. • NamedPerson is defined as IName. This means that you can only call the methods of IName on NamedPerson even though TPerson may have more methods than IName does.

But their use will, as I mentioned above, start you thinking about your code in new, interesting and powerful ways. A Simple Example First, they can be used to define a method signature that your code can call, but that can be defined later. This enables you to define a class that is open to additional functionality at run-time by consumers of that class. Here’s an example. Let’s say you want to create a simple calculator. You might do it like this: Understanding Anonymous Methods 48 type TCalculator = class function Add(x, y: integer): integer; function Subtract(x, y: integer): integer; end; ...

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