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It looks like AfxGetMainWnd() will return NULL if it is called from a non-GUI thread. ie. A Worker thread. Or of course if the main window in a GUI thread is not of type CMyMainWnd or derived from it.
Simple enough to test what AfxGetMainWnd() returns and ASSERT or log errors.
BTW. We can't see you <cast_type> You need to use the < and > and pre and code Formatting Toolbar options when embedding code in posts.
Neville Franks, Author of ED for Windows www.getsoft.com and coming soon: Surfulater www.surfulater.com
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No, AfxGetMainWnd() does not return NULL. How else could I get the Window caption? 
The thing is that the caption is correct, just the caption of the main window as it should be. So, I assume that AfxGetMainWnd() returns the correct window pointer, but the cast just fails.
And thanks for the hint on the < and >... I will keep that in mind next time.
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Neville Franks wrote:
BTW. We can't see you <cast_type> You need to use the < and > and pre and code Formatting Toolbar options when embedding code in posts.
It looks like it is:
return dynamic_cast<CMyMainWnd*>(AfxGetMainWnd());
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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why dynamic_cast and not static_cast?
~Nitron.
ññòòïðïðB A
start
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You'd have to ask Tak that one. I was simply helping Neville see potentially hidden text.
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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I have an ATL com dll and i want to get a function from it. The question is what is the syntax.
Lets say the name of my dll is: Test and the name of my function is getName ?.
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The syntax... the syntax of what?
The syntax of the function? Do you mean the function prototype, do you need to know the function's prototype?
Or perhaps you want to know how to go about calling that function.
Please clarify.
Regards,
Alvaro
Give a man a fish, he owes you one fish. Teach a man to fish, you give up your monopoly on fisheries.
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I want to know how to call the function.
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You'd do it the same way you call any COM method. First you need to get a hold of the COM object, and then you can call its method. There are several alternatives:
- Import the DLL's type library into your project. Look at the #import directive.
- Use the Class Wizard to add a class wrapper for the COM object. Open Class Wizard/Add Class/From a type library.
- Use one of the template classes like CComQIPtr (ATL), or com_ptr_t.
- Use the CoCreateInstance API.
If my memory serves me right the first option is the easiest -- look into it. Good luck!
Regards,
Alvaro
Give a man a fish, he owes you one fish. Teach a man to fish, you give up your monopoly on fisheries.
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 I use the fetch_row method for mysql and then retrieve the info from that field with a simple
value = row[i];
this works well with all other fields, but for some reason date fields only return me a 0000-00-00
does anyone know what's going on?
thanks in advance
If it's broken, I probably did it
bdiamond
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Hello,
I want to have a function that returns a vector.. I'm unsure on how to define this function.
here's how i define the vector..
class CXMLParser
{
public:
CXMLParser(CString strUrl);
virtual ~CXMLParser();
.... code snipped ......
public:
struct RSS_struct {
// Channel info.
CString strChannelTitle,
strChannelLink,
strChannelDescription,
strChannelDate;
// Item info.
CString strTitle,
strLink,
strDescription,
strDate;
};
std::vector<RSS_struct> v_RSS;
};
Whoever said nothing's impossible never tried slamming a revolving door!
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Include a method signature in your header file for the class, something like the following:
std::vector<RSS_struct> GetData();
Write your function in the .cpp file:
std::vector<RSS_struct> GetData()
{
std::vector<RSS_struct> vect;
RSS_struct data;
vect.push_back(data);
return vect;
}
Don't forget to #include <vector> and using namespace std;.
- Nick Parker
My Blog | My Articles
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Thank you!
Rob
Whoever said nothing's impossible never tried slamming a revolving door!
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First I recommend you typedef your vector type:
typedef std::vector<RSS_struct> RSSVector;
Then you can define your v_RSS like this:
RSSVector v_RSS;
This makes adding your member function easy:
RSSVector& GetRSSVector() { return v_RSS; }
Regards,
Alvaro
Give a man a fish, he owes you one fish. Teach a man to fish, you give up your monopoly on fisheries.
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I would advise against this, it makes your code unreadable. At least, it's made code I've had to maintain unreadable.
Christian
I have drunk the cool-aid and found it wan and bitter. - Chris Maunder
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As long as the typedefs are well named, I find that they can sometimes be helpful, since they reduce code complexity.
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I guess it's a matter of opinion. I've never had trouble reading STL code, or found it overly complex.
Christian
I have drunk the cool-aid and found it wan and bitter. - Chris Maunder
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You cannot say that this:
std::vector<RSS_struct>
is as concise as this:
RSSVector
And yes, you can throw in a "using std::vector" declaration and simplify a bit, but the non-typedef'd version is still longer. And really, how is a using declaration fundamentally different than a typedef? They both make code prettier by giving up a little bit of explicitness.
I tend to find that the angle brackets are unpleasant to look at, as well.
I'm not saying that typedefs are necessary. Nor am I saying that they should be used most of the time. But you said they make code unreadable, and I believe that's clearly not the case.
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Curi0us_George wrote:
You cannot say that this:
std::vector
is as concise as this:
RSSVector
No, but it has the advantage of being C++. I know what it means when I read it.
Curi0us_George wrote:
And yes, you can throw in a "using std::vector" declaration and simplify a bit
Seriously, who on earth DOESN'T do that ?
Curi0us_George wrote:
And really, how is a using declaration fundamentally different than a typedef?
It's valid C++, I know right away that it's lurking somewhere when I see vector without the std in code. I don't need to go looking for the using statement to decipher the vector variable. Not so your typedef.
Curi0us_George wrote:
I tend to find that the angle brackets are unpleasant to look at, as well.
That's your call. I find they make it easy for me to scan STL code to get to the bits I need to know what is going on.
Curi0us_George wrote:
But you said they make code unreadable, and I believe that's clearly not the case.
You're clearly wrong. My original statement was that they CAN make code unreadable. I've downloaded code, I think here from CP, and spent half a day deciphering it because it used a LOT of different STL container instances, and the typedef names they used were plain awful. It was like looking at a different programming language altogether.
Christian
I have drunk the cool-aid and found it wan and bitter. - Chris Maunder
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typedef is part of the C++ language, just like the using declaration. It is perfectly valid C++, and Stroustrup himself gave similar examples of when one might use typedefs. He said that "unsigned char" is really too long and unwieldy to use, so we might define "uchar". Same with vector<sometype>. It's often convenient to use a shorter synonym.
As for knowing that "vector" refers to "std::vector", you are wrong. You do not know when you see a vector reference with no namespace qualifier, that the vector is a std::vector. If you did, then C++ namespaces would be meaningless. Typically your assumption would be correct, but not always.
"You're clearly wrong. My original statement was that they CAN make code unreadable."
I don't really think I'm wrong. You said, "I would advise against this, it makes your code unreadable." RSS_vector was a fairly clear typedef. That's all I was saying. Rather than blaming the typedef functionality for poor clarity, blame the poor names. Poorly named classes also lead to poor clarity, but it's not a fault with the feature. It's a fault with the programmer.
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Curi0us_George wrote:
typedef is part of the C++ language, just like the using declaration. It is perfectly valid C++, and Stroustrup himself gave similar examples of when one might use typedefs. He said that "unsigned char" is really too long and unwieldy to use, so we might define "uchar". Same with vector. It's often convenient to use a shorter synonym.
Your first point is valid, and I am well aware that Stroustrup shows the use of typedefs in similar circumstances to those we are talking about. He also makes clear that C++ langauge features were included on the basis of how they could be used well, not excluded based on how they could be abused by the clueless. The designers of C# could have learned from this approach. What I'm saying is that just because you CAN typedef, does not mean you SHOULD. Stroustrup also says that macros should never be used, they are always a sign of a bad design or a bad programmer. A typedef is really not much different to one possible use of a macro, that of creating our own language ( exactly what Stroustrup warned against ), by creating new names for things that already exist.
Curi0us_George wrote:
Typically your assumption would be correct, but not always.
Which makes your comment obviously dumb. Yes, it's entirely possible that it would be referring to some other class called vector, but from my point of view, I'd be forgiven for assuming it was a std::vector, and if every time you see a vector in code you go searching to make sure that it's from namespace std, then I'm afraid you're being overly anal.
Curi0us_George wrote:
Rather than blaming the typedef functionality for poor clarity, blame the poor names. Poorly named classes also lead to poor clarity, but it's not a fault with the feature. It's a fault with the programmer.
And that's what I've said all along, my point is that I've seen code rendered illegible by poor use of a plethora of typedefs, and really at the end of the day it's my opinion that anyone too dumb to read STL code should probably give VB a try. I still don't see how the typedef helps anything, except for the lazy typist, and it still remains that you have to 'learn' the typedefs in a project unless they are so descriptive that they are as long as the thing they replace.
And I really doubt we have any chance of convincing each other, or that we're even 100% on the same page anymore.
Christian
I have drunk the cool-aid and found it wan and bitter. - Chris Maunder
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I don't think my comment about namespaces was dumb, but that's your opinion.
I also still think that typedefs can be useful, but you're right. This isn't going anywhere.
I do acknowledge that poorly named typedefs are a terrible, though.
- Derek
P.S. As for who doesn't use "using std::whatever", I typically don't. I normally use the fully qualified names, partly because I've worked with other classes with identical names before (e.g. vector), but mostly because I end up forgetting which one's I've declared and which ones I haven't. And when I use something new that I've forgotten to declare, the compiler complains. Frustrates me and wastes time. The same thing happens when I cut and paste and forget the using declarations. It typically turns out to be more energy efficient for me to just type the "std::" every time. I suppose I could add "using namespace std" to all of my files, but I consider importing entire namespaces to be poor style.
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Curi0us_George wrote:
I suppose I could add "using namespace std" to all of my files, but I consider importing entire namespaces to be poor style.
I agree 100%. I tend to include and use standard library components in stdafx, so I always know where to go to update my using std:: list. I make it alphabetical, so it's easy to scan.
Christian
I have drunk the cool-aid and found it wan and bitter. - Chris Maunder
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I would agree if the typedef names are cryptic, like the ones used in the STL. Unfortunately typedefs are often used only as abbreviations, and that's the wrong usage, IMHO. If you use descriptive names, like RSSVector, I think it actually makes the code more readable while cutting down on the typing.
What looks better?
std::vector<RSS> m_vector;
void GetVector(std::vector<RSS>& v);
or
RSSVector m_vector;
void GetVector(RSSVector& v);
Regards,
Alvaro
Give a man a fish, he owes you one fish. Teach a man to fish, you give up your monopoly on fisheries.
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