Uml序列图：与默认构造函数比较绘制新的运算符

Question

Could someone tell me the how to draw the differences in a sequence diagram with the following C++ code example. I tried to be as clear as possible:)

main

#include "classa.h"

int main()
{
    ClassA a;
    return 0;
}

classa.h

#ifndef CLASSA_H
#define CLASSA_H
#include "classb.h"

class ClassA
{
public:
    ClassA();
    ~ClassA();
private:
    ClassB *var1;
    ClassB var2;
};

#endif // CLASSA_H

classb.h

#ifndef CLASSB_H
#define CLASSB_H

class ClassB
{
public:
    ClassB();
    void test();
};

#endif // CLASSB_H

classa.cpp

#include "classa.h"

ClassA::ClassA()
{
    var1 = new ClassB;
    var1->test();
    var2.test();
}

ClassA::~ClassA()
{
    delete var1;
}

classb.ccp

#include "classb.h"

ClassB::ClassB()
{
}

void ClassB::test()
{
    //Here some code
}

I Think the image below is used for the new operator (var1), but how is var2 drawn?

Answer 1

My c++ is a bit rusty but I think something like this:

var2 gets allocated automatically when a is created - so is created before var1 . As far as UML is concerned, it's still creation of a new class instance. There may be ways to further stereotype the <<create>> operation to indicate creation on the stack vs. heap but can't say I've ever used them. Like I say though, my C++ is a bit rusty.

hth.