Difference between revisions of "Cpp Coding Standards/VIRTUAL"
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| − | + | === Virtual Classes (VIRTUAL) - Summary === | |
| + | ''These items refer to class hierarchies where the base class is virtual and the derived classes are intended to be used – at least sometimes – via pointers or references to the base class.'' | ||
| − | + | ===== Liskov Substitution Principle <span id="LSP">(LSP)</span> ===== | |
| − | + | Always follow the Liskov Substitution Principle: Everything a client can do with a base class, it must be able to do with each derived class as well. [[/LSP|-> Details]] | |
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| − | ==== Liskov Substitution Principle <span id="LSP">(LSP)</span> ==== | + | |
| − | Always follow the Liskov Substitution Principle: Everything a client can do with a base class, it must be able to do with each derived class as well. | + | |
| − | [[/ | + | ===== Instantiate Only Leaves <span id="Inst">(Inst)</span> ===== |
| + | In an inheritance tree of virtual classes, instantiate only the leaves. Make all other classes either abstract or their constructors protected, so instantiation is impossible. [[/Inst|-> Details]] | ||
| − | ==== | + | ===== Overrides <span id="Over">(Over)</span> ===== |
| − | + | Do not give overrides of a virtual function stronger preconditions or weaker postconditions. <br> | |
| + | Give them the same default values.<br> | ||
| + | Use the “virtual” keyword also on all overrides. [[/Over|-> Details]] | ||
| − | [[/ | + | ===== Right Destructor <span id="RightDestr">(RightDestr)</span> ===== |
| + | All virtual classes need a virtual destructor. If the class can not be instantiated, the destructor may be inline, else it has to be non-inline. <br> | ||
| + | Non-virtual mix-in classes need a protected destructor. [[/RightDestr|-> Details]] | ||
| − | ==== | + | ===== Non Virtual Interfaces <span id="NVI">(NVI)</span> ===== |
| − | + | If a class has more than one parallel derived class, use the Non Virtual Interface idiom. [[/NVI|-> Details]] | |
| − | + | ===== Safe Copying <span id="SafeCopy">(SafeCopy)</span> ===== | |
| − | + | If a virtual class needs to be copied via references to a base class, disable the copy constructor and operator=() in the base classes and implement the clone() idiom instead. [[/SafeCopy|-> Details]] | |
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| − | ==== Safe Copying <span id="SafeCopy">(SafeCopy)</span> ==== | + | |
| − | If a virtual class needs to be copied via references to a base class, disable the copy constructor and operator=() in the base classes and implement the clone() idiom instead. | + | |
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| − | [[/SafeCopy|Details]] | + | |
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Revision as of 11:14, 13 April 2007
Contents
Virtual Classes (VIRTUAL) - Summary
These items refer to class hierarchies where the base class is virtual and the derived classes are intended to be used – at least sometimes – via pointers or references to the base class.
Liskov Substitution Principle (LSP)
Always follow the Liskov Substitution Principle: Everything a client can do with a base class, it must be able to do with each derived class as well. -> Details
Instantiate Only Leaves (Inst)
In an inheritance tree of virtual classes, instantiate only the leaves. Make all other classes either abstract or their constructors protected, so instantiation is impossible. -> Details
Overrides (Over)
Do not give overrides of a virtual function stronger preconditions or weaker postconditions.
Give them the same default values.
Use the “virtual” keyword also on all overrides. -> Details
Right Destructor (RightDestr)
All virtual classes need a virtual destructor. If the class can not be instantiated, the destructor may be inline, else it has to be non-inline.
Non-virtual mix-in classes need a protected destructor. -> Details
Non Virtual Interfaces (NVI)
If a class has more than one parallel derived class, use the Non Virtual Interface idiom. -> Details
Safe Copying (SafeCopy)
If a virtual class needs to be copied via references to a base class, disable the copy constructor and operator=() in the base classes and implement the clone() idiom instead. -> Details
Related Rules
- CLSDESIGN:Inherit - How to Inherit
