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Inheritance Constructors & Overriden Functions
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More than meets the eye Objects always contain copy of parent class:
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Constructing/Destructing
Object built/destroyed in layers Base class constructed Geometric Object
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Constructing/Destructing
Object built/destroyed in layers Base class constructed Derived class constructed Geometric Object Circle
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Explicit Constructor Calls
Initialization list can specify parent constructor:
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Implicit Constructor Call
If no explicit call to parent constructor, get default added behind the scenes: Silently becomes
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When you have to… If a class does not provide no-arg constructor child classes must explicitly call one
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When you have to… If a class does not provide no-arg constructor child classes must explicitly call one
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When you have to… If derived class wants to set private variable and there is no set function:
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When you have to… Pass appropriate info to parent constructor, use rest to initialize your values
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Initialization List Can still use initializations list for own info
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Constructing/Destructing
Object built/destroyed in layers Base class constructed Derived class constructed Geometric Object Circle
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Constructing/Destructing
Object built/destroyed in layers Base class constructed Derived class constructed Derived class destroyed – clean up after itself Geometric Object
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Constructing/Destructing
Object built/destroyed in layers Base class constructed Derived class constructed Derived class destroyed – clean up after itself Base class destroyed – clean up after itself
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Overriden Functions
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Function Implementations
Functions redefined by child class normally use that version Geometric Object Circle
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Function Implementations
Scope resolution operator allows access to parent class version: Geometric Object Circle
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Function Implementations
Derived class can call Parent version Avoids code duplication!
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