NewB with C++ - Functions & Classes

Hi,

I'm new to C++ programming. I've used Qbasic in the past, as well as Borland Delphi, but I decided that I'd probably learn something as commenly known as C++

after reading through the tutorials here, I tried my hand on some of the possibilities, but I got stuck trying to figure functions out. Below is my code, I don't see why it shouldn't work...

Code:

---

#include <iostream>

using namespace std;

class PlayerObj // Standard way of defining the class
{
public:
  PlayerObj();
  // Constructor
  ~PlayerObj();
  // Destructor
  void setspeed ( int p );
  int readspeed();
  void Setdir ( int d );
  int Readdir();
  char Textface();
protected:

  int Playerspeed;
  int PlayerDir;
};

PlayerObj::PlayerObj()
{
  Playerspeed = 0;
  PlayerDir = 3;
}

PlayerObj::~PlayerObj()
{
        //Destructors do not accept arguments
}

void PlayerObj::setspeed ( int p )
{

  Playerspeed = p;
}
int PlayerObj::readspeed() 
{

  return Playerspeed;
}

void PlayerObj::Setdir (int d )
{
       
  PlayerDir = d;
}

int PlayerObj::Readdir()
{
       
        return PlayerDir;
}

char PlayerObj::Textface()
{
// Here's the problem... I've attempted to do it as depicted below this line,
// as well as the method depicted below that. Neither worked...
        if ( PlayerDir > 8 ) { Playerdir = 1 ; }
        if ( Player1.Readdir() == 1 ) return "Up";
        if ( Player1.Readdir() == 2 ) return "Up + Right";
        if ( Player1.Readdir() == 3 ) return "Right";
        if ( Player1.Readdir() == 4 ) return "Right + Down";
        if ( Player1.Readdir() == 5 ) return "Down"
        if ( Player1.Readdir() == 6 ) return "Down + Left";
        if ( Player1.Readdir() == 7 ) return "Left";
        if ( Player1.Readdir() == 8 ) return "Left + Up;"
 }

int main()
{
  PlayerObj Player1; 
 
  Player1.setspeed ( 100 );

  cout<< Player1.readspeed();
  cout<<"\nPlayer1 is facing: "<< Player1.Textface() <<"\n";
 
  cin.get();

}

---

I'm probably missing something really obvious, but it doesn't compile telling me that "PlayerDir" is undeclared, or with the other approach, Player1.

Any help would be appreciated!

Within a class method, you can't refer to the instance that is being used. So inside of Textface you shouldn't be mentioning Player1. Your first attempt was the right idea, but you just need to pay attention to case: Playerdir is different than PlayerDir.

Also, your Textface method is returning a char. A char holds only a single character, you want a string of characters known in programming simply as a string. The C++ string class is included in <string>. Use that instead of char.

Code:

---


class PlayerObj // Standard way of defining the class
{
public:
  PlayerObj();
  // Constructor
  ~PlayerObj();
  // Destructor
  void setspeed ( int p );
  int readspeed();
  void Setdir ( int d );
  int Readdir();
  char Textface();  // You're trying to return a string, so make this a string
protected:

  int Playerspeed;
  int PlayerDir;
};

char PlayerObj::Textface()  // This should be a const char*
{
// Here's the problem... I've attempted to do it as depicted below this line,
// as well as the method depicted below that. Neither worked...
        if ( PlayerDir > 8 ) { Playerdir = 1 ; }  // Syntax Error
        if ( Player1.Readdir() == 1 ) return "Up";  // Remove the object name, you only want the function name
        if ( Player1.Readdir() == 2 ) return "Up + Right"; // These are not characters
        if ( Player1.Readdir() == 3 ) return "Right";
        if ( Player1.Readdir() == 4 ) return "Right + Down";
        if ( Player1.Readdir() == 5 ) return "Down" // Syntax Error
        if ( Player1.Readdir() == 6 ) return "Down + Left";
        if ( Player1.Readdir() == 7 ) return "Left";
        if ( Player1.Readdir() == 8 ) return "Left + Up;"  // Syntax Error
 }

---

[/QUOTE]

Problem one, char's only hold one character.

Code:

---

#include <string>

---

And make that function

Code:

---

string Textface();

---

And fix the defination as well.

This line:

Code:

---

        if ( PlayerDir > 8 ) { Playerdir = 1 ; }

---

Does not work because the second PlayerDir does not have the D capitalized.


No, the rest of your if statements in this function.
Player1? No. You are thinking of object oriented programming all wrong.
Your class is an object called PlayerObj

When you declare a object of type player object in main

Code:

---

PlayerObj player1

---

player1 is now that object. You can not in your object definition (the class) specify a specific object name.
Uhh…if that makes sense. Just remove the player1. part of all those lines (and a few of them are missing the ; at the end.

*edit* Beat while typing!

Some other comments:

Code:

---

void setspeed ( int p );
int readspeed();
void Setdir ( int d );
int Readdir();

---

Inconsistency in the capitalization here can be confusing for other potential users of your class (and even yourself perhaps). If other people have to use this class, they might stumble on why the 'r' in readspeed is lowercase and why the 'R' in Readdir is uppercase. I would suggest you pick a naming convention to use throughout the class and stick to it. You even have differences in the capitalization of the 'd' between the Setdir and Readdir member functions and the PlayerDir member variable... very confusing.

Code:

---

if ( PlayerDir > 8 ) { PlayerDir = 1 ; }
if ( Player1.Readdir() == 1 ) return "Up";
if ( Player1.Readdir() == 2 ) return "Up + Right";
if ( Player1.Readdir() == 3 ) return "Right";
if ( Player1.Readdir() == 4 ) return "Right + Down";
if ( Player1.Readdir() == 5 ) return "Down"
if ( Player1.Readdir() == 6 ) return "Down + Left";
if ( Player1.Readdir() == 7 ) return "Left";
if ( Player1.Readdir() == 8 ) return "Left + Up;"

---

Again there is a matter of consistency, why directly access the PlayerDir value in the first line there and then turn around and use the Readdir functions on every other line to access the value. I'd personally stick to just directly accessing the value to save on the overhead of the function call. Also, there is the matter of the validation check of the PlayerDir value in the first line. Since this value is protected (should be private unless you plan on doing some inheritance with the class later on) and is only set via the Setdir member function (other than in the constructor), then it would seem that the Setdir function should be the place to validate and reset that:

Code:

---

void PlayerObj::Setdir (int d )
{
    if( d > 8 ) d = 1;
    PlayerDir = d;
}

string PlayerObj::Textface()
{
    if ( PlayerDir == 1 ) return "Up";
    else if ( PlayerDir == 2 ) return "Up + Right";
    else if ( PlayerDir == 3 ) return "Right";
    else if ( PlayerDir == 4 ) return "Right + Down";
    else if ( PlayerDir == 5 ) return "Down"
    else if ( PlayerDir == 6 ) return "Down + Left";
    else if ( PlayerDir == 7 ) return "Left";
    else return "Left + Up;"
 }

---

Just my thoughts on the matter.

Thanks everyone, that cleared the whole bunch up :)

By the way, Would anyone know how to get some simple figures on the screen without having to download the 212MB DirectX SDK?

Quote:

---

Originally Posted by Rider

Thanks everyone, that cleared the whole bunch up :)

By the way, Would anyone know how to get some simple figures on the screen without having to download the 212MB DirectX SDK?

---

You can use the GDI function just as TextOut() function. You will need to create a windows API program with a window to diaply the text on.

Quote:

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Originally Posted by Quantum1024

You can use the GDI function just as TextOut() function. You will need to create a windows API program with a window to diaply the text on.

---

Would this allow me to create simple forms and shapes besides just plain text?

How would I create a windows API program, and window?

The first thing you need is a windows compiler, like Dev-C++.

>> Would anyone know how to get some simple figures on the screen without having to download the 212MB DirectX SDK?

check out sdl.. lots of fun

http://www.libsdl.org

Quote:

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Originally Posted by xhi

>> Would anyone know how to get some simple figures on the screen without having to download the 212MB DirectX SDK?

check out sdl.. lots of fun

http://www.libsdl.org

---

It looks allright, but I can't seem to figure out how to get the package running in Dev-C++ once I downloaded it.

It seems like I have all the files, I just don't know what to do with 'em...

here you go... good luck

http://www.libsdl.org/cgi/docwiki.cg...0Dev_2dC_2b_2b

You usually need to change the project options to include the extra libraries. But I'm sure that's in the link provided.

It's kind of difficult to get the right bits of information, especially when several sites tell me varying things about how to get SDL to work.

I run Windows 2000.

My Dev-C++ is installed in: C:\Devtools\Dev-cpp
I added the libraries as explained in the link above.
I've moved the DLL's to my new project's directory (My documents\Code 'n such\Tutorials\Tstprj)

but compiling the code from THIS tutorial, doesn't work. First the complier tells me that SDL.h can't be found, setting up the #include to include to full path of that file, seems to work...

but then I get another compiler error, namely "cannot find -lSDLmain"

What's wrong, and what do I need to fix before it'll just be nice and compile?

Code:

---

#if defined(_MSC_VER)
#include "SDL.h"
#else
#include "SDL/SDL.h"
#endif

---

Assuming thats the code you were using when you tried to compile..

If you have put the SDL includes in the include path by doing this

>> Create an \SDL directory in the \include subdirectory of your Dev-C++ installation root, and copy all of the SDL header files into this new directory.

then you should not be quoting the includes.. it should be

<SDL/SDL.h>

one thing to watch is that some older tutorials show it as

<SDL.h>

the newer versions of SDL have changed to putting SDL in its own dir under the include path, so you should do like I mentioned before and use

#include <SDL/SDL.h>

As for the libs error.. did you do this
>> Copy SDL.dll and libSDLmain.a from the SDL library into the \lib subdirectory of your Dev-C++ installation root.

and

>> Click the Parameters tab, and in the Linker textbox enter "-lmingw32 -lSDLmain -lSDL -lSDL_mixer" (without the quotes) then click Ok.

>> It's kind of difficult to get the right bits of information, especially when several sites tell me varying things about how to get SDL to work.

Well Im going to add to that list you have.. :)

This is where I got the tutorials when I started.. he has not updated for a while but there are 4 or 5 tuts there that will get you clear up to making a side scrolling shooter... I dont know if this stuff even compiles with the newer versions of SDL, I know there have been some changes recently.. it would however be well worth a shot, as he has clear examples and explanations and wrote the code well enough also..

http://cone3d.gamedev.net/cgi-bin/in...s/gfxsdl/index

also you cant go wrong digging around the docs on the sdl site.. http://libsdl.org

I have set it up exactly as posted before (a couple of times) and added the stuff to my project's parameters tab, but it still tells me that it can't find lSDLmain

all the lib files in the Dev-cpp\lib folder
all the .h files in the Dev-cpp\include folder

though the <SDL\SDL.h> thing did work exactly as it's supposed to, compiling still won't work...

I have now tried to point to the .a and .lib files manually in parameters, but then I get a whole bunch of errors before even the first line of code.

Code:

---

C:\DevTools\Dev-Cpp\lib\libSDL.a(SDL_systimer.o)(.text+0x15) In function `SDL_StartTicks':
  [Linker error] undefined reference to `timeBeginPeriod@4'
  [Linker error] undefined reference to `timeGetTime@0'

 C:\DevTools\Dev-Cpp\lib\libSDL.a(SDL_systimer.o)(.text+0xc1) In function `SDL_GetTicks':
  [Linker error] undefined reference to `timeGetTime@0'

---

and the list goes on.

I'd just like to get this thing running so I can do some coding :)

any help is appreciated

Quote:

---

I've moved the DLL's to my new project's directory (My documents\Code 'n such\Tutorials\Tstprj)

---

I thought there was only one DLL. SDL.DLL (which I put in the path).

Did you add the libraries to the project options?

Well I found out something stupid and fixed it, I forgot to add the library directories to the "directories" tab in my project...

that fixed most of my anguish, but now I'm getting a Makefile error...

Compile Log:

Code:

---

Executing  make...
mingw32-make -f "C:\Documents and Settings\Administrator\My Documents\
Code and such\Tutorials\Tstprj\Makefile.win" all
mingw32-make: Nothing to be done for `all'.

Execution terminated

---

I really appreciate all the help so far... I'd just like to get this all done