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Published byHomer Simon Modified over 9 years ago
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Intro to COM What is it and what can it do for me?
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COM Defined COM (Component Object Model) and DCOM (Distributed COM) are a set of binary and network standards for the modeling of objects and their communications.
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OK, What are Components? Components are big brother of Classes. Component = Object Interface = Function Set of that Object Properties = Member Variables –(all Properties are actually get & put calls) Methods = Functions BONUS: Components can have more than one interface.
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What makes up a Component? Implementation object Interface object(s) IFooExIFoo Implementation Object IUnknown Components are well-encapsulated objects
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Identifiers GUID (globally unique identifiers) –are stored in 16-byte (128 bit) structures CLSID (class identifier GUID) IID (interface identifier GUID) IUnknown QueryInterface –Returns a pointer to requested Interface AddRef –Increases the RefCount Release –Decreases the RefCount
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Where do components live? In-Process servers (.dll) Out-of-Process servers (.exe) Remote servers (.exe) ActiveX (.ocx)
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Using Components Rapid Application Development Seamless application updates Build great apps without reinventing the wheel Interface different systems with ease Examples: Serial port communications, Scanner image capture, Image archive systems, internet server interaction (CDDB)
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What languages can I use? C++, Java, Visual Basic and VB Script (IIS) ActiveX technology, Use MS ATL (VC++) Component creation Component use in applications
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Why should you learn COM? Saves tremendous time (after the initial learning curve) Use of existing objects Object Reuse: C++ tried to address this issue, but just made it easy to reuse source code. So you can use DCOM.
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Parallel Programming Three main types of applications: –CPU intensive graphics rendering BFA –Resource Specific DCOM lets you do this seamlessly –Highly connected custom data, application structures hybrid memory models
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Cradle - Traveling Salesman
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6min 30 sec 16 sec
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197 days 3.5 Days
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Life 3D
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Life3D face relationships 21 43 56 1 5 62 3 4
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Symera Viewer
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Clustering Scenarios Tight Coupling Loose Coupling
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Life3D Class Conversion CMainWindowCFaceWindow CCubeFace (interface) CFace (implementation) CSymObjCSymObjRef Original classes New classes Symera base classes CCubeFace CSymObj User Interface Distributed Object
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Recommended Reading Dr. GUI articles on COM - a MUST READ Essential COM by Don Box Inside COM & Inside Distributed COM (MS Press) ActiveX/COM Control Programming (WROX Press) For the complete history and theory, read: –Inside OLE (MS Press)
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