uuid.h File Reference

Detailed Description

A UUID is a sequence of 16 bytes that is unique throughout the universe, and which can uniquely identify anything you might want. It will never have a name conflict with any other UUID. To come up with a UUID of your own, run the 'uuidgen' program that comes with many Unix and Windows systems. Although any UUID is guaranteed to be unique, there is a downside: it's almost impossible for a human to read, understand, or remember the contents of a UUID. For a less unique, human-readable alternative to UUIDs, see IMoniker.

A UUID is what is known as a "strong name". It is like the name of a class in a C++ program, or of a global variable, but the "strong" part refers to how this name, unlike the name of a C++ class, is unique and refers precisely to this one thing. C++ names are "weak names", it is very easy to create two different things with the same name, for example, classes named "String" are very common, and two different "String" classes could not be used in the same program. When making a single program, it is possible to avoid these conflicts, but with a component system, you never know how components will be used together, thus the need for strong names.

The UUID is the standard way of looking up and indexing objects in XPLC. All "well-known" objects you need to look for (such as the standard XPLC moniker and category services, and other objects you create yourself) will have a UUID you can look up using the service manager. Note that objects referenced by a UUID are necessarily "singletons" - that is, objects of a class that is only instantiated once in any program. For example, a factory that produces HelloWorld objects would have its own UUID - so you can ask for a HelloWorldFactory and get "the" HelloWorldFactory - but the HelloWorld objects it produces would not be findable by UUID. (If they all had the same UUID, it wouldn't be very Universally Unique, would it? And if they all had different UUIDs, how would you know which UUID to look for?)

Also: when you retrieve a different interface from an IObject using its getInterface() method, you do so by looking up the UUID of that interface, also known as an IID (which is just a nickname for UUID, they are identical in meaning). Every interface must have an IID, but the IID is the same for all objects implementing that interface. However, you can have multiple objects implementing a particular interface, and each of those objects will have its own UUID.

Define Documentation

#define DEFINE_IID	(	iface,
		u1,
		u2,
		u3,
		u4,
		u5,
		u6,
		u7,
		u8,
		u9,
		u10,
		u11	)

Value:

static const UUID iface##_IID = u1, u2, u3, u4, u5, u6, u7, u8, u9, u10, u11; \
template <> \
struct XPLC_IID<iface> { \
  static const UUID& get() { \
    return iface##_IID; \
  } \
}

Used to define the IID of an interface.


Compounds
struct	_GUID
	The structure underlying UUIDs. More...
struct	XPLC_IID
	An Interface IDentifier. More...
Defines
#define	DEFINE_IID(iface, u1, u2, u3, u4, u5, u6, u7, u8, u9, u10, u11)
	Used to define the IID of an interface.

uuid.h File Reference

Compounds

Defines

Detailed Description

Define Documentation

Typedef Documentation