It is unclear whether this code is part of your Poll/Wait event loop. If it is, then you shouldn't be calling SDL_GetMouseState(), you should read all your data from the event. If not, you should not rely on the event, but instead only use the information provided by SDL_GetMouseState().

You need to store the fact that you are dragging the object.

Here is a reasonably simple example, dragging a rectangle around the screen. It uses the event based model, for maximum clarity (at the expense of being maybe a little more verbose).

#include <iostream>
#include <cstdlib>

#include "SDL.h"

bool intersects(int objectX, int objectY, int dimensions, int mouseX, int mouseY)
{
if(mouseX < objectX || mouseY < objectY)
{
return false;
}

if(mouseX > objectX + dimensions || mouseY > objectY + dimensions)
{
return false;
}

return true;
}

int main(int, char **)
{
if(SDL_Init(SDL_INIT_VIDEO) < 0)
{
std::cerr << "Failed to initialise SDL: " << SDL_GetError() << '\n';
return 1;
}

std::atexit(&SDL_Quit);

SDL_Surface *screen = SDL_SetVideoMode(600, 600, 0, 0);
if(!screen)
{
std::cerr << "Failed to set video mode: " << SDL_GetError() << '\n';
return 1;
}

const Uint8 Button = SDL_BUTTON_LEFT;
const int Dimensions = 30;
int x = (screen->w - Dimensions) / 2;
int y = (screen->h - Dimensions) / 2;
bool running = true;
bool dragging = false;
int offsetX = 0;
int offsetY = 0;
while(running)
{
SDL_Event event;
while(SDL_PollEvent(&event))
{
if(event.type == SDL_QUIT)
{
running = false;
}
else if(event.type == SDL_KEYDOWN)
{
if(event.key.keysym.sym == SDLK_ESCAPE)
{
running = false;
}
}
else if(event.type == SDL_MOUSEBUTTONDOWN)
{
if((event.button.button & Button) == Button && intersects(x, y, Dimensions, event.button.x, event.button.y))
{
offsetX = event.button.x - x;
offsetY = event.button.y - y;
dragging = true;
}
}
else if(event.type == SDL_MOUSEBUTTONUP)
{
if((event.button.button & Button) == Button && dragging)
{
offsetX = 0;
offsetY = 0;
dragging = false;
}
}
else if(event.type == SDL_MOUSEMOTION)
{
if(dragging)
{
x = event.motion.x - offsetX;
y = event.motion.y - offsetY;
}
}
}

SDL_FillRect(screen, 0, 0);
SDL_Rect dest = { x, y, Dimensions, Dimensions };
SDL_FillRect(screen, &dest, SDL_MapRGB(screen->format, 0xff, 0x00, 0x00));
SDL_Flip(screen);
}

return 0;
}


What parts of my code do you have difficulty understanding? Have you tried running it? Playing with it, seeing how it works?
[/quote]
First of as you asked before im not polling events in the main loop, Im handling events in a class.. Maybe i could give you a idea on what my game is about.. I have a class for my player " class Car " .. I handle events, move the car etc.. In the handle events im trying to drag someother object which is initialized in the main loop, It's an arrow down object.. I have all its coordinates, width, height etc set.. My aim is when the car collides with the arrow, The car changes its direction downwards. I have all the collision working perfectly, But my problem is i cant drag the object to wherever i want, I hope you understand.

It is OK to be a beginner, we all were beginners once. However, I will not just fix your code for you. I put quite a bit of effort into writing that example, I compiled and tested it too. You'll need to meet me half way, and the key step to doing this is to address the parts you don't understand.
[/quote]
Im not asking you to fix my code, Im just asking help, It is just yesterday i started using mouse events, cause, i never use mouse events, only keyboard events, I somehow learnt the basics and i ended up with the code which is not working.. Here is my code to drag the object.

void Car::handle_events()
{
int x, y;
dragging = false;

if( event.type == SDL_MOUSEBUTTONDOWN )
{
if( event.button.button == SDL_BUTTON_LEFT )
{
x = event.motion.x;
y = event.motion.y;

if( ( x > arrowdown.x ) && ( x < arrowdown.x + arrowdown.w ) && ( y > arrowdown.y ) && ( y < arrowdown.y + arrowdown.h ) )
{
dragging = true;
}
}
}
if( event.type == SDL_MOUSEBUTTONUP )
{
if( event.button.button == SDL_BUTTON_LEFT )
{
dragging = false;
}
}

if( event.type == SDL_KEYDOWN )
{
switch( event.key.keysym.sym )
{
case SDLK_SPACE:
xVel = 0;

}
}
else if( event.type == SDL_KEYUP )
{
switch( event.key.keysym.sym )
{
case SDLK_SPACE:
xVel = 5;
}
}
}

void Car::drag()
{
if( dragging == true )
{
arrowdown.x = event.motion.x;
arrowdown.y = event.motion.y;
}
}

Should i be more precise..?

Should i be more precise..?

You need to poll events somewhere. Since it isn't in your car class, it must be in the code that calls handle_events(). If you aren't actively polling events, the values of a SDL_Event are meaningless - they will not reflect the current state of the inputs.
[/quote]
I know, I handle events in the handle_events() functions and i poll it in the main loop by myCar.handle_events();

I'm not sure I really understand. I imagine you have a top down view. There is a little care that races around a maze or something. The player can start and stop the car, but perhaps not control its direction directly. They can instead place little arrows in the path of the car, that changes the car from moving horizontally to vertically. The players job is to build a set of arrows to get the car from the start to the destination, without hitting anything.
[/quote]
Yes you are right, There are 3 types of arrows, arrowdown, arrowright, arrowup, But the problem is i cant drag it..

My example code shows how to do it correctly. Your code needs to achieve the same overall "flow", even though it is structured differently.
[/quote]
I did exactly as you gave the example, Only thing i couldnt understand is.. What is offsetX and offsetY, i changed all the other things from the example to my project, Yet i cant get it working..

I think having two classes would be better, one for the Car and one for the Arrow. The car can concentrate on reacting to keyboard events. The arrow can worry about getting dragged and dropped. Finally, you have the calling code that checks for collisions, and notifies the car (and the arrow, if necessary) about these collisions.
[/quote]
Its tough to have classes for 3 different types of arrows and calling them in functions would be tough, so i just initialize them in the main loop, it doesnt make a big difference i guess..