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class initialized array

Hi

how can I initialize a const char* myarr[] in a class constructor?

class Myclass {
const char* myarr[] = { "abc", "def" };
....
};
Myclass::Myclas s():
myarr[]( ??? )
{}

thanks
Nov 8 '06 #1
14 2123
Gary Wessle wrote:
how can I initialize a const char* myarr[] in a class constructor?
You cannot. Nobody can. No way to do that.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
Nov 8 '06 #2
You need to add the static keyword.

class MyClass
{
public:

MyClass(){}
~MyClass(){}

static const char * myarr[];
};

const char * MyClass::myarr[] = {"abc", "def" };

Nov 8 '06 #3
Gary Wessle wrote:
how can I initialize a const char* myarr[] in a class constructor?

class Myclass {
const char* myarr[] = { "abc", "def" };
...
};
Myclass::Myclas s():
myarr[]( ??? )
{}
Use a vector of strings rather than an array of char pointers
(http://www.parashift.com/c++-faq-lit...html#faq-34.1), and
then use an initializer helper class:

template<typena me T>
class Initializer
{
vector<Tv_;
public:
Initializer( size_t reserveSize=0 ) { v_.reserve( reserveSize ); }
Initializer& Add( const T& t ) { v_.push_back(t) ; return *this; }
operator vector<T>() const { return v_; }
};

class Myclass {
const vector<stringmy arr;
public:
Myclass()
: myarr( Initializer( 2 )
.Add( "abc" )
.Add( "def" ) )
{}
};

Cheers! --M

Nov 8 '06 #4
XtremDev wrote:
You need to add the static keyword.

class MyClass
{
public:

MyClass(){}
~MyClass(){}

static const char * myarr[];
};

const char * MyClass::myarr[] = {"abc", "def" };
What if it's not static data?

Cheers! --M

Nov 8 '06 #5

mlimber a écrit :

What if it's not static data?

Cheers! --M
your solution ;o)

Nov 8 '06 #6
Gary Wessle wrote:
...
how can I initialize a const char* myarr[] in a class constructor?

class Myclass {
const char* myarr[] = { "abc", "def" };
...
};
Myclass::Myclas s():
myarr[]( ??? )
{}
...
In this context arrays support only one initializer syntax: '()'-initializer,
which leads to zero-initialization.

In your case one way around is to declare the array with explicitly specified size

class Myclass {
const char* myarr[2];
...
};

and use assignment instead of initialization

Myclass::Myclas s()
{
myarr[0] = "abc";
myarr[1] = "def";
}

--
Best regards,
Andrey Tarasevich
Nov 8 '06 #7
Andrey Tarasevich wrote:
Gary Wessle wrote:
...
how can I initialize a const char* myarr[] in a class constructor?

class Myclass {
const char* myarr[] = { "abc", "def" };
...
};
Myclass::Myclas s():
myarr[]( ??? )
{}
...

In this context arrays support only one initializer syntax: '()'-initializer,
which leads to zero-initialization.

In your case one way around is to declare the array with explicitly specified size

class Myclass {
const char* myarr[2];
...
};

and use assignment instead of initialization

Myclass::Myclas s()
{
myarr[0] = "abc";
myarr[1] = "def";
}
Right, although probably the pointers should almost certainly be const
also
(http://www.parashift.com/c++-faq-lit...html#faq-18.1),
which would eliminate this possibility.

Cheers! --M

Nov 8 '06 #8
mlimber wrote:
>...
and use assignment instead of initialization

Myclass::Myclas s()
{
myarr[0] = "abc";
myarr[1] = "def";
}

Right, although probably the pointers should almost certainly be const
also
...
That's something only the OP knows.

--
Best regards,
Andrey Tarasevich
Nov 8 '06 #9

Gary Wessle wrote:
Hi

how can I initialize a const char* myarr[] in a class constructor?

class Myclass {
const char* myarr[] = { "abc", "def" };
...
};
Myclass::Myclas s():
myarr[]( ??? )
{}

thanks
You could deal with allocating a pointer in the ctor body.
But thats old school stuff and frankly: much more work and way too
fragile.
You can only initialize an array with default values.
example:

template< typename T, const size_t Size >
MyClass
{
T array[ Size ];
MyClass() : array() { } // init elements to
// whatever the default T() might be
};

A std::string doesn't suffer from that handicap.

#include <iostream>
#include <ostream>
#include <string>

template < typename T >
class MyClass
{
T m_t;
public:
MyClass(const T& t) : m_t(t) { }
friend
std::ostream&
operator<<(std: :ostream& os, const MyClass& r_my)
{
return os << r_my.m_t;
}
};

int main()
{
MyClass< std::string instance("abc def");
std::cout << instance << std::endl; // so simple

return 0;
}

Nov 8 '06 #10

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