avoiding repeated code in initialization lists

[cppaddict]

If you have a class with:

1. Many members

2. Two or more constructors

and if you follow the C++ FAQ guidelines of initializing all member
variables in a contructor initialiazation list, then you might have
two constructors that repeat much of the same code:

MyClass() :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
...etc...
{}

MyClass(int x, int y) :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
...etc...
{
// does some stuff with x and y
}

How can you avoid this unnecessary repetition?

Thanks for any ideas,
cpp

 

[John Harrison]

If you have a class with:

1. Many members

2. Two or more constructors

and if you follow the C++ FAQ guidelines of initializing all member
variables in a contructor initialiazation list, then you might have
two constructors that repeat much of the same code:

MyClass() :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
...etc...
{}

MyClass(int x, int y) :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
...etc...
{
// does some stuff with x and y
}

How can you avoid this unnecessary repetition?

Thanks for any ideas,
cpp

One way is to factor out the common code into another class, usually making
that other class a base class.

class MyClassBase
{
public:
MyClassBase() :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
{
}
protected:
int _member1;
int _member2;
string _member3;
double _member4;
};

class MyClass : public MyClassBase
{
public:
MyClass() {}
MyClass(int x, int y)
{
// do something with x and y
}
};

john

 

[Maxim Yegorushkin]

If you have a class with:

1. Many members

2. Two or more constructors
[]

How can you avoid this unnecessary repetition?

You might like using boost::value_initialized<>. It takes care of member default initialization.

 

[AciD_X]

If you have a class with:

1. Many members

2. Two or more constructors

and if you follow the C++ FAQ guidelines of initializing all member
variables in a contructor initialiazation list, then you might have
two constructors that repeat much of the same code:

MyClass() :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
...etc...
{}

MyClass(int x, int y) :
_member1(0),
_member2(0),
_member3("default string")
_member4(0.0)
...etc...
{
// does some stuff with x and y
}

How can you avoid this unnecessary repetition?

Thanks for any ideas,
cpp

Instead of overloading the constructors, You might consider using default
parameters. This may or may not be appropriate, depending on how the
class and the constructors are designed ...