member initialization

[josh]

Hi,

if I've:

class Date
{
public:
Date(int m, int d, int y);
}

Date::Date(int m, int d, int y)
{
....
}


and then a class in which I've another object:
class A
{
public:
A(int, int, int);

private:
Date d;
}
A::A(int m, int d, int y) : d(m, d, y)
{
...
}
above is the only method to initialize objects?
I can't do:
A::A(int m, int d, int y)
{
d(m, d, y);
}

Correct?

[s_amrollahi@yahoo.com]

Re: member initialization


josh äæÔÊå ÇÓÊ:

Hi,
>
if I've:
>
class Date
{
public:
Date(int m, int d, int y);
}
>
Date::Date(int m, int d, int y)
{
...
}
>
>
and then a class in which I've another object:
class A
{
public:
A(int, int, int);
>
private:
Date d;
}
A::A(int m, int d, int y) : d(m, d, y)
{
..
}
above is the only method to initialize objects?
I can't do:
A::A(int m, int d, int y)
{
d(m, d, y);
}
>
Correct?

Yes. Because Date has no Default Coonstructor, So it should be
initialized using member initialization list in A's constructor.

Regards

[eriwik@student.chalmers.se]

Re: member initialization

s_amrollahi@yah oo.com wrote:

josh äæÔÊå ÇÓÊ:

Hi,

if I've:

class Date
{
public:
Date(int m, int d, int y);
}

Date::Date(int m, int d, int y)
{
...
}


and then a class in which I've another object:
class A
{
public:
A(int, int, int);

private:
Date d;
}
A::A(int m, int d, int y) : d(m, d, y)
{
..
}
above is the only method to initialize objects?
I can't do:
A::A(int m, int d, int y)
{
d(m, d, y);
}

Correct?

Yes. Because Date has no Default Coonstructor, So it should be
initialized using member initialization list in A's constructor.

Yes, and even if you did have a default constructor it would still be
the best way to initialize the object, since if you didn't a
Date-object would first be created and then replaced with the one with
the right date set. Using an initializer-list you only create one
Date-object.

--
Erik Wikström

[LR]

Re: member initialization

eriwik@student. chalmers.se wrote:

s_amrollahi@yah oo.com wrote:
>
>

>>josh äæÔÊå ÇÓÊ:
>>

>>>Hi,
>>>
>>>if I've:
>>>
>>>class Date
>>>{
>> public:
>> Date(int m, int d, int y);
>>>}
>>>
>>>Date::Date(i nt m, int d, int y)
>>>{
>>>...
>>>}
>>>
>>>
>>>and then a class in which I've another object:
>>>class A
>>>{
>>>public:
>> A(int, int, int);
>>>
>>>private:
>> Date d;
>>>}
>>>A::A(int m, int d, int y) : d(m, d, y)
>>>{
>>>..
>>>}
>>>above is the only method to initialize objects?
>>>I can't do:
>>>A::A(int m, int d, int y)
>>>{
>> d(m, d, y);
>>>}
>>>
>>>Correct?

>>
>>Yes. Because Date has no Default Coonstructor, So it should be
>>initialized using member initialization list in A's constructor.

>
>
Yes, and even if you did have a default constructor it would still be
the best way to initialize the object, since if you didn't a
Date-object would first be created and then replaced with the one with
the right date set. Using an initializer-list you only create one
Date-object.

So efficiency is more important then, say readability? Because I'd find
this a little bit clearer

A a(Date(11,15,20 06));

then this:

A a(11,15,2006);

Of course, I'm supposing that Date has a copy ctor, and A has a ctor
that looks like:

A::A(const Date &dateArgumen t) : d(dateArgument) {}

I think this also has the advantage of being a little more flexible if
for some reason Date gets new ctors. After all, you have a Date that is
a member of A, why expose, even as data initializers, the component
members of Date in A's ctor?


And even if Date didn't have a copy ctor, but had getters for m, d and y
(month, day and year might be better names?) I would still think that
having a ctor in A that looked like this would be clearer (even if it
was a lot less efficient):

A::A(const Date &dateArgumen t)
:
d(dateArgument. month(), dateArgument.da y(), dateArgument.ye ar())
{}

But then, your application and YMWV.


LR