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added a rule about DoXXX() functions

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@4046 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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Vadim Zeitlin 1999-10-18 13:17:43 +00:00
parent ce1a1ff40a
commit ae8b97cf4b
1 changed files with 68 additions and 6 deletions
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@ -59,8 +59,8 @@ C++ portability guide</A> by David Williams.
<LI><A HREF="#no_warnings">Turn on all warnings and eradicate them</A></LI>
<LI><A HREF="#no_assume_sizeof">Don't rely on <TT>sizeof(int) == 2</TT>...</A></LI>
<LI><A HREF="#no_assignment_in_if">No assignments in conditional expressions</A></LI>
<LI><A HREF="#no_comment_code">Use <TT>#if 0</TT> rather than comments to temporarily
disable blocks of code</A></LI>
<LI><A HREF="#no_comment_code">Use <TT>#if 0</TT> rather than comments to temporarily disable blocks of code</A></LI>
<LI><A HREF="#no_overloaded_virtuals">Avoid overloaded virtual functions</A></LI>
<LI><A HREF="#no_extra_semicolon">Don't use extra semi-colons on top level</A></LI>
</OL>
<BR>
@ -76,10 +76,8 @@ C++ portability guide</A> by David Williams.
<LI>Style choices</LI>
<OL>
<LI><A HREF="#naming_conv">Naming conventions: use <TT>m_</TT> for members</A></LI>
<LI><A HREF="#no_void_param">Don't use <TT>void</TT> for functions without
arguments</A></LI>
<LI><A HREF="#no_const_int">Don't use <TT>const</TT> for non pointer/reference
arguments</A></LI>
<LI><A HREF="#no_void_param">Don't use <TT>void</TT> for functions without arguments</A></LI>
<LI><A HREF="#no_const_int">Don't use <TT>const</TT> for non pointer/reference arguments</A></LI>
</OL>
</UL>
@ -464,6 +462,70 @@ instead of
The reason is simple: if there are any <TT>/* ... */</TT> comments inside
<TT>...</TT> the second version will, of course, miserably fail.
<P><LI><A NAME="no_overloaded_virtuals"></A><B>Avoid overloaded virtual functions</B></LI><P>
You should avoid having overloaded virtual methods in a base class because if
any of them is overriden in a derived class, then all others must be overriden
as well or it would be impossible to call them on an object of derived class.
For example, the following code:
<PRE>
class Base
{
public:
virtual void Read(wxFile& file);
virtual void Read(const wxString& filename);
};
class Derived : public Base
{
public:
virtual void Read(wxFile& file) { ... }
};
...
Derived d;
d.Read("some_filename"); // compile error here!
</PRE>
will fail to compile because the base class function taking <TT>filename</TT>
is hidden by the virtual function overriden in the derived class (this is
known as [virtual] function name hiding problem in C++).
<P>
The standard solution to this problem in wxWindows (where we have such
situations quite often) is to make both <TT>Read()</TT> functions not virtual
and introduce a single virtual function <TT>DoRead()</TT>. Usually, it makes
sense because the function taking a filename is (again, usually) implemented
in terms of the function reading from a file anyhow (but making only this
functions not virtual won't solve the above problem!).
<P>
So, the above declarations should be written as:
<PRE>
class Base
{
public:
void Read(wxFile& file);
void Read(const wxString& filename);
protected:
virtual void DoRead(wxFile& file);
};
class Derived : public Base
{
protected:
virtual void DoRead(wxFile& file) { ... }
};
</PRE>
This technique is widely used in many of wxWindows classes - for example,
<TT>wxWindow</TT> has more than a dozen of <TT>DoXXX()</TT> functions which
allows to have many overloaded versions of commonly used methods such as
<TT>SetSize()</TT>
<P><LI><A NAME="no_extra_semicolon"></A><B>Don't use extra semi-colons on top level</B></LI><P>
Some compilers don't pay any attention to extra semicolons on top level, as in
<PRE>