Scope of std::vector

[Steve]

I have defined the following private object:

std::vector<Ban ana> bananas;

in my header file. I have also added a method called FillVector(), which
sets the size of the vector and fills it with Banana objects.

In another method (getSecondBanan a()) I want to access the contents of
bananas, using e.g.

Banana second_banana;
second_banana = bananas[1];

Unfortunately my program crashes when I try to do it like this. However it
*does* work when I fill the vector in the same method as I try to access the
contents of this. This suggests to me that the scope of the vector is
restricted to the method it is filled in. How do I set the scope of such an
object so that it can be accessed from anywhere within the class?

[Sumit Rajan]

"Steve" <st***@hello.co m> wrote in message
news:kv******** ********@newsfe 3-gui.ntli.net...

"Sumit Rajan" <su*********@gm ail.com> wrote in message
news:3r******** ****@individual .net...

Could you please post some code that demonstates your problem? Please
remember to keep it minimal and compile-able:
http://www.parashift.com/c++-faq-lit...t.html#faq-5.8
I get error Unhandled exception at 0x00415329 in ClientTestClass es.exe:
0xC0000005: Access violation reading location 0x000002c4. It's something
to do with the way I'm filling and/or accessing the vector.

I need to get RequestCall() to return a call from the call_list vector.

/* Manager.cpp */

void Manager::Login( )
{
proxy.FillVecto rs(); /* fills the vector in ClientProxy */
proxy.RequestCa ll(current_camp aign); /* crash occurs in this method */
}

The code is not complete, compile-able or minimal. :-)

However, take a look at the comments below and let me know if it fixes your
problem.

/* ClientProxy.h */
#ifndef __CLIENTPROXY__
#define __CLIENTPROXY__
#include "Call.h"
#include "Campaign.h "
#include "User.h"
#include "vector"
using namespace std;
Not a great idea to have a using directive in a header file.

class ClientProxy

{

public:
ClientProxy();
User Login(const std::string& sname, const std::string& ip, int pn);
Campaign RequestCampaign s(User u);
Call RequestCall(Cam paign c);
bool MarshallRequest ();

void FillVectors();

private:
/* Test variables below */
Call GetNextCall();
int call_counter;

/* Real vars */
Call current_call;
Campaign current_campaig n;
User user;
vector<Campaign > campaigns;
vector<Call> call_list;
Okay... two interesting members: call_list and campaigns.
};
/* END CLASS DEFINITION ClientProxy */

#endif

/* ClientProxy.cpp */

#include "ClientProx y.h"
#include "Call.h"
#include <vector>

ClientProxy::Cl ientProxy()
{

}

void ClientProxy::Fi llVectors()
{
printf("\n-FillVectors()") ;
vector<Campaign > campaigns(5);
Now you're defining another vector called "campaigns" . Remember that this is
a local one -- only valid here within this function.

//Consider skipping the above line and using vector<>::reser ve(). Something
like:
//campaigns.reser ve(5);

//Alternatively, you could initialize the vector to the size you want in the
initializer list
//for ClientProxy().
campaigns[0] = Campaign(1, "Camp1");
campaigns[1] = Campaign(2, "Camp2");
campaigns[2] = Campaign(3, "Camp3");
campaigns[3] = Campaign(4, "Camp4");
campaigns[4] = Campaign(5, "Camp5");
And you make changes to your local "campaigns" . None of all this affects the
data member by the same name.

vector<Call> call_list(5);

Same problem here. We got a local "call_list" and changes made are only to
the local "call_list" .

Regards,
Sumit.
--
Sumit Rajan <su****@msdc.hc ltech.com>

[Sumit Rajan]

"Sumit Rajan" <su*********@gm ail.com> wrote in message
news:3r******** ****@individual .net...

"Steve" <st***@hello.co m> wrote in message
news:kv******** ********@newsfe 3-gui.ntli.net...

"Sumit Rajan" <su*********@gm ail.com> wrote in message
news:3r******** ****@individual .net...

Could you please post some code that demonstates your problem? Please
remember to keep it minimal and compile-able:
http://www.parashift.com/c++-faq-lit...t.html#faq-5.8

I get error Unhandled exception at 0x00415329 in ClientTestClass es.exe:
0xC0000005: Access violation reading location 0x000002c4. It's something
to do with the way I'm filling and/or accessing the vector.

I need to get RequestCall() to return a call from the call_list vector.

/* Manager.cpp */

void Manager::Login( )
{
proxy.FillVecto rs(); /* fills the vector in ClientProxy */
proxy.RequestCa ll(current_camp aign); /* crash occurs in this method */
}

The code is not complete, compile-able or minimal. :-)

However, take a look at the comments below and let me know if it fixes
your problem.

/* ClientProxy.h */
#ifndef __CLIENTPROXY__
#define __CLIENTPROXY__
#include "Call.h"
#include "Campaign.h "
#include "User.h"
#include "vector"
using namespace std;

Not a great idea to have a using directive in a header file.

class ClientProxy

{

public:
ClientProxy();
User Login(const std::string& sname, const std::string& ip, int pn);
Campaign RequestCampaign s(User u);
Call RequestCall(Cam paign c);
bool MarshallRequest ();

void FillVectors();

private:
/* Test variables below */
Call GetNextCall();
int call_counter;

/* Real vars */
Call current_call;
Campaign current_campaig n;
User user;
vector<Campaign > campaigns;
vector<Call> call_list;

Okay... two interesting members: call_list and campaigns.

};
/* END CLASS DEFINITION ClientProxy */

#endif

/* ClientProxy.cpp */

#include "ClientProx y.h"
#include "Call.h"
#include <vector>

ClientProxy::Cl ientProxy()
{

}

void ClientProxy::Fi llVectors()
{
printf("\n-FillVectors()") ;
vector<Campaign > campaigns(5);

Now you're defining another vector called "campaigns" . Remember that this
is a local one -- only valid here within this function.

//Consider skipping the above line and using vector<>::reser ve().
Something like:
//campaigns.reser ve(5);

//Alternatively, you could initialize the vector to the size you want in
the initializer list
//for ClientProxy().

Or you could skip the above line (vector<Campaig n> campaigns(5);)
entirely and just use
campaigns.push_ back(...);
every time you want to add an element to the vector.

Regards,
Sumit.
--
Sumit Rajan <su****@msdc.hc ltech.com>

[Steve]

"Sumit Rajan" <su*********@gm ail.com> wrote in message
news:3r******** ****@individual .net...

Or you could skip the above line (vector<Campaig n> campaigns(5);)
entirely and just use
campaigns.push_ back(...);
every time you want to add an element to the vector.

Thanks Sumit, it works a treat. :)

[Ali Çehreli]

"Steve" <st***@hello.co m> wrote in message
news:kv******** ********@newsfe 3-gui.ntli.net...

"Sumit Rajan" <su*********@gm ail.com> wrote in message
news:3r******** ****@individual .net... /* ClientProxy.h */ #ifndef __CLIENTPROXY__
#define __CLIENTPROXY__
__CLIENTPROXY__ is a reserved name. Quoting from the standard with my
formatting:

<quote>
17.4.3.1.2 Global names

1 Certain sets of names and function signatures are always reserved to the
implementation:

-- Each name that contains a double underscore (_ _) or begins with an
underscore followed by an uppercase letter (2.11) is reserved to the
implementation for any use.

-- Each name that begins with an underscore is reserved to the
implementation for use as a name in the global namespace.165)

[...]

Footnote 165) Such names are also reserved in namespace ::std (17.4.3.1).
</quote>

[...]

Also, you included "vector" in ClientProxy.h:
#include "vector"
[...]
/* ClientProxy.cpp */

#include "ClientProx y.h"
#include "Call.h"
Then you included <vector> in ClientProxy.cpp
#include <vector>

Though I doubt that it has anything to do with your problems, those two
headers are potentially different, because the rules for finding headers
(e.g. searching in directory paths) are different between "" and <> headers.

Ali