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Node or NodeI ?

rc_hzrc_hz Member Eric RCOrganization: www.genband.comProject: No project yet ✭✭✭
Page 368 in Ice 3.1.0 document:
12.8.1Instantiating a Servant
  Instantiating a servant means to allocate an instance:    
      Node servant = new NodeI("Fred");
      
  This code creates a new NodeI instance and assigns its address to a reference of 
  type Node. This works because NodeI is derived from Node, so a Node reference
  can refer to an instance of type NodeI. [color="Red"]However, if we want to invoke a
  member function of the NodeI class at this point, we must use a NodeI reference[/color]:
      NodeI servant = new NodeI("Fred");
  
  Whether you use a Node or a NodeI reference [color="red"]depends purely on whether you
  want to invoke a member function of the NodeI class[/color]: if not, a Node reference
  works just as well as a NodeI reference.


That is, the document emphasizes that if we want to invoke a member function of the XXXI class, we must use a XXXI reference instead of XXX interface reference. Can you explain a little more why ?

Further, in %ICEJ_HOME%\demo\book\simple_filesystem\Server.java:
	[b]File file[/b] = new FileI("README", root);                                      
	String[] text;                                                              
	text = new String[] { "This file system contains a collection of poetry." };
	try {                                                                       
		[b]file.write(text, null);[/b]
	} catch (GenericError e) {                                                  
		System.err.println(e.reason);                                       
	}                                                                           

Are they inconsistent ?

Thank you !

Comments

  • marcmarc FloridaAdministrators, ZeroC Staff Marc LaukienOrganization: ZeroC, Inc.Project: The Internet Communications Engine ZeroC Staff
    What is meant here are member functions of NodeI that are not defined in the Slice definition of Node.
  • rc_hzrc_hz Member Eric RCOrganization: www.genband.comProject: No project yet ✭✭✭
    marc wrote:
    What is meant here are member functions of NodeI that are not defined in the Slice definition of Node.
    Thanks. So it is just a problem of inheritance. I think this paragraph is a little misleading.
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