nsComponentManager
nsServiceManager
No restrictions. You can call any function from the static classes nsComponentManager and nsServiceManager. XPCOM will do the right @@ -40,8 +79,8 @@ it is only in Init_XPCOM() do we create register the RegistryFactory() with the ComponentManager.
Init_XPCOM()@@ -67,7 +106,8 @@ from both NS_GetGlobalComponentManager() and NS_GetGlobalServiceManager() we will be safe.-Is there a global Registry being maintained
+Is there a global +Registry being maintainedNo. The nsIRegistry is designed to be lightweight access to the registry. Consumers who need to access the registry should use the @@ -79,7 +119,8 @@ is going to be a major headach.
-ComponentManager Vs ServiceManager
+ComponentManager +Vs ServiceManagerComponentManager is the only way for component creation. ComponentManager always uses the component's factory @@ -95,36 +136,42 @@ to exist. Hence the notion of getting a service not creating one. (as opposed to the notion of Creating instances with the componentManager). ServiceManager is a convenience because components can technically force singletonism by making their factory return the same instance if one was created already. -The other big use of ServiceManager is the (still unimplemented) notion -of Shutting down a service. +The +other big use of ServiceManager is the (still unimplemented) notion of +Shutting down a service.Client
Should a component do anything at creation to become a Service -
- When does a client use the service manager vs component manager
-
When a client knows that the component that -they are trying to instantiate is a singleton, they need to call service -manager instead of component manager. Clients dont have to worry about -calling the ComponentManager at all in this case. The ServiceManager will -take care of creating the instance if the first one doesn't exist already. +
++
When a client knows that the component that they +are trying to instantiate is a singleton, they need to call service manager +instead of component manager. Clients dont have to worry about calling +the ComponentManager at all in this case. The ServiceManager will take +care of creating the instance if the first one doesn't exist already.
-- When does a client use the Component Manager as opposed to Service Manager
-
When a client wants a private instance of -a component, they call the Component Manager. From the Clients point of -view, a new xpcom object creation happens everytime they call CreateInstance() -Anything else is an implementation detail that the Client need not worry -about. +
++
When a client wants a private instance of a component, +they call the Component Manager. From the Clients point of view, a new +xpcom object creation happens everytime they call CreateInstance() Anything +else is an implementation detail that the Client need not worry about.
-- How does a Client know that they have to instantiate a singleton
-
For now, the Client just has to know. There -is no way of telling which component is a Service and which isn't. In fact, +
++
For now, the Client just has to know. There is +no way of telling which component is a Service and which isn't. In fact, in todays xpcom (Mar 1999) any component can be accessed as a Service. Use your judgement until there is a proper method or service manager is eliminated. There is nothing even in the code that detects Services from @@ -138,7 +185,9 @@ dp@netscape.com
- Can a component enforce use only as a Service
-
No. The notion of the ServiceManager is available +
++
No. The notion of the ServiceManager is available only to Clients.
Note that at some points when a component wants another component, it actually behaves as a client and hence follows the @@ -164,26 +213,30 @@ the same object will be returned hence guaranteeing singletonism.
No. Again, the notion of a ServiceManager -is available only to Clients. +
++
No. Again, the notion of a ServiceManager is available +only to Clients.
-Can a component advertise that it is a service so clients can use it as one -
No. There isn't a way other than a comment in the interface of the -header file. +
++
No. There isn't a way other than a comment in the interface of the header +file.
-ProgID Vs CLSID
+ProgID Vs CLSIDClassID or CLSID is the unique indentification of a component. It is a structure of huge numbers generated by using uuidgen on a windows box. It is represented as a string in documentation as {108d75a0-bab5-11d2-96c4-0060b0fb9956}+ +ProgID is the string identification of an implementation of a component -the client is looking for. The representation takes a URI syntax. Eg. component://netscape/network/protocol&name=http -Some simplify this to, ProgID is a more readable string form of a CLSID. +the client is looking for. The representation takes a URI syntax. Eg. component://netscape/network/protocol?name=http;description=Http%20Protocol%20Handler +
Some simplify this to, ProgID is a more readable string form of a CLSID. That is acceptable on the periphery. The ProgID is a Client thing. Components register with component manager to claim that they are the implementation for a ProgID. A component can register to be the implementation for multiple @@ -191,23 +244,42 @@ ProgIDs (not implemented yet).Client
+implementation of a component. +
- -Should CreateInstance() calls use ProgID or CLSID
+ +
-
-ProgID is what Clients should use to CreateInstances. Clients should +Should CreateInstance() calls use ProgID or CLSID
ProgID is what Clients should use to CreateInstances. Clients should not even know about the CLSID unless they are hell bent on creating a particular -implementation of a component.
-- -
- Component+Should Components register with both a CID and ProgID -
- -Should Components register with both a CID and ProgID
-
-
-Absolutely.
+
Absolutely. ++How to debug components ?
+ +Since components are dynamically loaded only on demand, debugging +them could be a hard. Here are some tips to debugging components. +Windows: VC5.0 VC6.0 +
Include your component library in the Project->Settings, Additional +Dll. drop down. After that breakpoints can be enabled. +
+Unix: gdb +
Let the program run until you are sure that your component +is loaded. Type Control-C. Now all symbols from your component will be +available in gdb. Put your breakpoints and restart the app. Gdb will complain +that it cannot set the breakpoint, and that it is temporarily disabling +it, but when the *.so is loaded, the breakpoint is enabled automatically. +- <Eric Van Der Poel>+Mac: Codewarrior +
Just open the appropriate .xSYM file in the debugger; the debugger +will target the library when the application is run. - <Simon +Fraser>+
diff --git a/xpcom/doc/xpcom-component-registration.html b/xpcom/doc/xpcom-component-registration.html index 7b2a90cbf871..89658cdbdddc 100644 --- a/xpcom/doc/xpcom-component-registration.html +++ b/xpcom/doc/xpcom-component-registration.html @@ -151,7 +151,8 @@ do to salvage this situation other than warning the user of possible instability and advice a restart upon which the re-registration will happen.ProgID Spec
-Let us consider some more examples: +The general format of ProgIDs is component://netscape/compname?var=value;var=value;var=value... +Let us consider some more examples:
- A pluggable protocol that implementes the nfs protocol
@@ -176,31 +177,31 @@ they particularly do.The ProgID for these would look like
{Assume proper escaping of all above URI}
- -component://netscape/network-protocol&type=nfs
+component://netscape/network-protocol?type=nfs- -component://netscape/data-converter&type=application/x-zip
+component://netscape/data-converter?type=application/x-zip- -component://netscape/plugin&type=image/gif&name=ImageMedia's -Gif Image Plugin&Description=Reders GIF Images....
+component://netscape/plugin?type=image/gif;name=ImageMedia Gif Image +Plugin;Description=Reders GIF Images....- -component://netscape/widget&type=toolbar
+component://netscape/widget?type=toolbar- -component://netscape/rdf/datsource&type=mail
+component://netscape/rdf/datsource?type=mail- -component://netscape/helperapp&type=application/postscript
+component://netscape/helperapp?type=application/postscriptThe above semantics would let ProgID be an extensible mechanism that could be searched on multiple ways. And
query on a progid should match only whatever was passed in. So a query for -
component://netscape/plugin&type=image/gif should pass for the -progid specified above. We could extend this +
component://netscape/plugin?type=image/gif should pass for the progid +specified above. We could extend this
mechanism with wildcards, but I dont want to go there yet... :-)