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This question regards application design and does not have a source code component. Is it common practice, or good practice, to use an abstract class and and multiple interfaces (small i) together in the same application? Consider the example of an abstract class automobile. This general class would enforce the "is a" constraints of all automobile types. Several different interface(s) would be defined and applied to the subclasses of automobile based on the type of automobile being defined. Does this seem reasonable? Or does defining an abstract class and multiple interfaces seem like over-kill?
Hello, This is a beginner's question regarding the "creating errors messages" (pp 381) and the "putting it all together" (pp 415). I'd appreciate if someone could clarify some of the code. In page 318, in the HTML after the paragraph "With that HTML, elem.parentNode refers to the DIV, so appending a new child results in: ..." 1) Shouldn't the span in this HTML have a class = 'error', which was assigned in step 4 ? 2) Why do we need to add a class = 'error' to the span and to the label anyway? I am assuming it is for changing the CSS but I don't see it used in the "Putting it all together" code of page 415. In page 415-420, "Putting it all together": 1) Why do we need the class = "two" in each DIV ? 2) How the CSS was manipulated to change the labels with error to red color. Thank you very much for your help.
hi using a static counter variable in a class lets us to count the number of objects created so far is there a way to to access all Live objects instantiated from a class.(not just the number of them but the names of them !) i want to write a simple code for a human class . and in its __construct method i want that object to say hello to all previously created objects!
First, thanks to both of you for writing the book and for how well the content is explained. However I'm having trouble understanding this statement on page 260: From what I can find via Google searches and tinkering with the pets4.cpp code, having a method in the derived class with the same name (different signature or not) as one in the base class hides the base class method, much like overriding a method seems to. Can you maybe explain that in a different way so it makes more sense to me? Thanks in advance!