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POConstructor in class with inheritance
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  1. POConstructor in class with inheritance
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    copied!<p>I'm having some problems with inheritance and constructors in C++. What I've got is a class <code>VirtualMotor</code> which inherits <code>Motor</code> (is that the correct way to say it?). The class VirtualMotor should have it's own constructor, but I'm doing something wrong when I create it and the compiler gives me an error (se below). My source code is like this:</p> <h3>Motor.h</h3> <pre><code>class Motor { protected: float speed; float angle; public: Motor(); float getSpeed(); float getAngle(); virtual void setSpeed( float speed ); virtual void setAngle( float angle ); </code></pre> <h3>Motor.cpp</h3> <pre><code>#include "Motor.h" float Motor::getSpeed() { return speed; } float Motor::getAngle() { return angle; } </code></pre> <h3>VirtualMotor.h</h3> <pre><code>#include "Motor.h" class VirtualMotor: public Motor { private: float lastSpeed; public: VirtualMotor(); void setSpeed(float speed); void setAngle(float angle); }; </code></pre> <h3>VirtualMotor.cpp</h3> <pre><code>#include "VirtualMotor.h" VirtualMotor::VirtualMotor() { speed = 2; angle = 5; } void VirtualMotor::setSpeed(float speed) { this-&gt;speed = speed; } void VirtualMotor::setAngle(float angle) { this-&gt;angle = angle; } </code></pre> <h3>Main.cpp</h3> <pre><code>#include &lt;iostream&gt; #include "VirtualMotor.h" using namespace std; int main (int argc, char **argv) { VirtualMotor m; cout &lt;&lt; m.getSpeed() &lt;&lt; endl; m.setSpeed(9); cout &lt;&lt; m.getSpeed() &lt;&lt; endl; return 0; } </code></pre> <p>To compile I use the command <code>g++ Main.cpp Motor.cpp VirtualMotor.cpp -o main</code> and I get the following error:</p> <pre><code>/tmp/ccIdYJaR.o: In function `VirtualMotor::VirtualMotor()': VirtualMotor.cpp:(.text+0x29): undefined reference to `Motor::Motor()' /tmp/ccIdYJaR.o: In function `VirtualMotor::VirtualMotor()': VirtualMotor.cpp:(.text+0x5d): undefined reference to `Motor::Motor()' /tmp/ccIdYJaR.o:(.rodata._ZTI12VirtualMotor[typeinfo for VirtualMotor]+0x8): undefined reference to `typeinfo for Motor' collect2: ld returned 1 exit status </code></pre> <p>I feel there's a really simple solution to this, but I just can't see it. I've tried to use <code>VirtualMotor::VirtualMotor() : Motor::Motor()</code> and other variations without any luck.</p>
 

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