dmmg1176@uxa.cso.uiuc.edu (David M Marcovitz) (03/01/91)
I am working with 3 classes (call them Foo, Bar, and Baz). Foo and
Bar are subclasses of Baz. There header files are as follows:
-----------Foo.h-----------
#define _H_Foo /* prevents file from being included more than once */
#include Baz.h /* superclass header */
#include Bar.h /* other file's header */
struct Foo : Baz
{
Bar *myBar; /* an object of the Bar class */
.
.
};
----------Bar.h------------
#define _H_Bar
#include Baz.h
#include Foo.h
struct Bar : Baz
{
Foo *myFoo; /* an object of the Foo class */
.
.
};
---------------------------
The problem is that I want each Foo to know about a Bar, and I want
each Bar to know about a Foo. Unfortunately I get a syntax error when
I try to compile. When compiling Bar.h, it first has to compile
Foo.h. When Foo.h tries to declare myBar, it can't because the Bar
class has not been; thus I get a syntax error.
How can I get around this problem?
--
David M. Marcovitz | internet: marcovitz@uiuc.edu
Computer-based Education Research Lab | dmmg1176@uxa.cso.uiuc.edu
University of Illinois | novanet: marco / cca / cerlolson@bootsie.uucp (Eric K. Olson) (03/01/91)
In article <1991Feb28.223430.24645@ux1.cso.uiuc.edu> dmmg1176@uxa.cso.uiuc.edu (David M Marcovitz) writes: > >-----------Foo.h----------- >#define _H_Foo /* prevents file from being included more than once */ > >#include Baz.h /* superclass header */ >#include Bar.h /* other file's header */ > >struct Foo : Baz >{ > Bar *myBar; /* an object of the Bar class */ > . > . >}; > >----------Bar.h------------ >#define _H_Bar > >#include Baz.h >#include Foo.h Leave this #include out > >struct Bar : Baz >{ > Foo *myFoo; /* an object of the Foo class */ change this to: struct Foo *myFoo; > . > . >}; >--------------------------- This works equivalently, but does not require the Foo.h header file. For another example, see CPanorama, which needs to use CScrollPane, which already #included CPanorama. -Eric -- Eric K. Olson, Editor, Prepare() NOTE: olson@bootsie.uucp doesn't work Lexington Software Design Internet: olson@endor.harvard.edu 72A Lowell St., Lexington, MA 02173 Uucp: harvard!endor!olson (617) 863-9624 Bitnet: OLSON@HARVARD
rac@macro.co.jp (Robert Coie) (03/04/91)
In article <1991Feb28.223430.24645@ux1.cso.uiuc.edu>, dmmg1176@uxa.cso.uiuc.edu (David M Marcovitz) writes: >> I am working with 3 classes (call them Foo, Bar, and Baz). Foo and >> Bar are subclasses of Baz. There header files are as follows: >> >> [header files containing mutually recursive Think C classes] >> >> The problem is that I want each Foo to know about a Bar, and I want >> each Bar to know about a Foo. Unfortunately I get a syntax error when >> I try to compile. When compiling Bar.h, it first has to compile >> Foo.h. When Foo.h tries to declare myBar, it can't because the Bar >> class has not been; thus I get a syntax error. >> >> How can I get around this problem? When you define a new class with struct Foo : Baz{}, Think C automatically generates a typedef struct Foo{} Foo; statement for you, enabling you to use the name Foo when referring to instances of this class. I think that the following two structures are similar enough to your Foo and Bar classes to illustrate the problem: typedef struct foo { bar *theBar; } foo; typedef struct bar { foo *theFoo; } bar; As in your example, this will generate a syntax error. Try rewriting it without relying on the typedef: typedef struct foo { struct bar *theBar; } foo; typedef struct bar { struct foo *theFoo; } bar; For more information on this, check the sources for CScrollPane and CPanorama, which are also mutually recursive, or look in your favorite C book about structure tags and incomplete types. -- +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Robert Coie Love is a vast exaggeration of the difference rac@macro.co.jp between one person and everybody else. - GBS