WRT below code, Abc & Xyz are 2 classes.
I get a reference in DoOperation(Xyz& temp) and want to assign it to a class data member ie mem1, so that this reference can be used by other member functions lile DOOperation_2(), DOOperation_3() etc..
I know we can't declare a reference in C++ without initialization. But how do I handle such a scenario in C++ ?
class Abc
{
public:
Xyz& mem; //ILLEGAL IN C++
void DoOperation(Xyz& temp)
{
mem = temp;
}
void DOOperation_2()
{
}
DOOperation_3()
{
}
};
It's simple: Use a pointer. Unlike references, pointers are assignable.
class Abc
{
public:
Xyz* mem1;
void DoOperation(Xyz& temp)
{
mem1 = &temp;
}
};
As you correctly noted, you need to initialize the reference . You also cannot change what a reference "points" to after it has been initialized .
So the simple solution here is to just use a pointer
class Abc {
public:
Xyz* mem1{nullptr};
void DoOperation(Xyz* ptr) {
mem1 = ptr;
}
};
And then you can use mem1
later on in a method like this (with a nice assert
)
void Abc::SomeMethod() {
assert(this->mem1);
mem1->something();
}
Note that a reference is very similar to a T* const
(const pointer). The key differences are outlined nicely in this answer Difference between const. pointer and reference?
If you absolutely have to use a reference, the only thing you can do is to initialize a reference in a constructor during initialization.
class Abc {
public:
Xyz& mem1;
Abc(Xyz& mem1_in) : mem1{mem1_in} {}
};
Initialize it in constructor:
class Abc
{
public:
Xyz& mem1;
Abc (xYZ& temp) : mem1(temp) {}
// ...
};
or use pointer:
class Abc
{
public:
Xyz* mem = nullptr;
void DoOperation(xYZ& temp)
{
mem = &temp;
}
// ...
};
Use a pointer instead.
class Abc
{
public:
Xyz* mem1; // pointer
void DoOperation(xYZ& temp)
{
mem1 = &temp; // take the address of the variable and save it to the pointer
}
void DOOperation_2()
{
}
DOOperation_3()
{
}
};
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