using collections in c++

[tessellated]

Hi all,

I want to iterate through a collection and at each item in the
collection access a particular property. In C# i know how to do this
easily, but with c++ I am a bit mystified Below is some sample code to
give you an idea of what i am trying to do.


SPGlobalAdmin * globAdmin = new SPGlobalAdmin();
SPVirtualServerCollection * servers = globAdmin->VirtualServers;
SPVirtualServer * vserver;
for (i = 0; i < servers->Count; i++)
{
//access properties of each vserver here
}

If this were c# I would just use a foreach loop like this

SPGlobalAdmin globAdmin = new SPGlobalAdmin();
foreach (SPVirtualServer vServer in globAdmin.VirtualServers)
{
string url = vServer.Url;
}


How to do this with c++?

 

[Carl Daniel [VC++ MVP]]

Hi all,

I want to iterate through a collection and at each item in the
collection access a particular property. In C# i know how to do this
easily, but with c++ I am a bit mystified Below is some sample code to
give you an idea of what i am trying to do.


SPGlobalAdmin * globAdmin = new SPGlobalAdmin();
SPVirtualServerCollection * servers = globAdmin->VirtualServers;
SPVirtualServer * vserver;
for (i = 0; i < servers->Count; i++)
{
//access properties of each vserver here
}

If this were c# I would just use a foreach loop like this

SPGlobalAdmin globAdmin = new SPGlobalAdmin();
foreach (SPVirtualServer vServer in globAdmin.VirtualServers)
{
string url = vServer.Url;
}


How to do this with c++?

If you're using C++/CLI (VC++ 2005) then you can use for each (note the
space) just as you would in C#. Otherwise, read on.


What kind of a collection is SPVirtualServersCollection? Each collection
class has some API to allow access to it's members. In the framework
classes, this API is usually expressed as IEnumerable, IList, ICollection,
IDictionary (or their generic equivalents in 2.0), or a combination of
these.

The C# foreach statement simply packages usage of the IEnumerable API into a
neat bit of syntactic sugar.

foreach (T t in C)
{
// stuff
}

is 100% equivalent to (and translated by the compiler literally to):

IEnumerator e = C.GetEnumerator();
while (e.MoveNext())
{
T t = (T)e.Current;

// stuff
}

You can use the same code in Managed C++ (VS2002/2003) to access framework
collections.

Of course, if you're talking about a C++ native collection such as a
std::vector, or on of the MFC collection classes, then they have different
APIs - but I gather that's not the kind of collection you're talking about.

-cd

 

[tessellated]

Well, I'm using VS2003 so the foreach option is not available. I did
discover the IEnumerator and that is working well, so that makes me
happy!

But now for my other issue. I need to grab the server's url out of the
collection in the form of a char*. The problem is addr below is of type
System::String and I don't know how to convert over.


System::Collections::IEnumerator * iEnum = NULL;
SPGlobalAdmin * globAdmin = new SPGlobalAdmin();
SPVirtualServerCollection * servers = globAdmin->VirtualServers;
iEnum = servers->GetEnumerator();

System::String * addr;
while(iEnum->MoveNext())
{
SPVirtualServer * vs =
static_cast<SPVirtualServer*>(iEnum->get_Current());
addr = vs->Url->ToString();
}

 

[Carl Daniel [VC++ MVP]]

Well, I'm using VS2003 so the foreach option is not available. I did
discover the IEnumerator and that is working well, so that makes me
happy!

But now for my other issue. I need to grab the server's url out of the
collection in the form of a char*. The problem is addr below is of
type System::String and I don't know how to convert over.


System::Collections::IEnumerator * iEnum = NULL;
SPGlobalAdmin * globAdmin = new SPGlobalAdmin();
SPVirtualServerCollection * servers = globAdmin->VirtualServers;
iEnum = servers->GetEnumerator();

System::String * addr;
while(iEnum->MoveNext())
{
SPVirtualServer * vs =
static_cast<SPVirtualServer*>(iEnum->get_Current());
addr = vs->Url->ToString();
}

See System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi

-cd