keyboard event not loading in cpp for sdl - c++

Question

I am trying to make it my screen print hello when I click the a key... And switch images when I press the 2 key... however when I do, nothing happens, I'm not sure why... it does not give me an error for some weird reason... if you have any ideas please let me know in the comments below. I have listed the code there!
#include <SDL.h>
#include <iostream>
int main(int argc, char* argv[])
{
SDL_Window* window = nullptr;
SDL_Surface* WindowSurface = nullptr;
SDL_Surface* image1 = nullptr;
SDL_Surface* image2 = nullptr;
SDL_Surface* currentImage = nullptr;
SDL_Init(SDL_INIT_VIDEO);
window = SDL_CreateWindow("sdl Window",
SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480,
SDL_WINDOW_SHOWN);
WindowSurface = SDL_GetWindowSurface(window);
image1 = SDL_LoadBMP("Red_sheet_full_2.bmp");
image2 = SDL_LoadBMP("Red_sheet_fullA.bmp");
currentImage = image2;
bool isRunning = true;
SDL_Event ev;
while (isRunning)
{
while (SDL_PollEvent(&ev) != 0);
{
if (ev.type == SDL_QUIT)
isRunning = false;
else if (ev.type == SDL_KEYDOWN)
{
switch (ev.key.keysym.sym)
case SDLK_a:
printf("hello");
break;
switch (ev.key.keysym.sym)
case SDLK_2:
currentImage = image1;
break;
}
}
SDL_BlitSurface(currentImage, NULL, WindowSurface, NULL);
SDL_UpdateWindowSurface(window);
}
SDL_FreeSurface(image1);
SDL_FreeSurface(image2);
SDL_DestroyWindow(window);
currentImage = image1 = image2 = nullptr;
window = nullptr;
SDL_Quit();
return 0;
}

Answer 1

The problem is in the switch statement. The break is outside the switch so, if the first event you receive is not an SDLK_a, it will break out of the while loop before printing hello and exit.
Here's a simplified version of what's happening: https://godbolt.org/z/9eEcEYGhj
#include <iostream>
int main(int argc, char* argv[])
{
while (true)
{
char c{'p'};
switch (c)
case 'a':
std::cout << "a\n";
break; // exits without printing anything
switch (c)
case 'b':
std::cout << "b\n";
break;
std::cout << c;
}
}
You have different ways to fix it.
One would be to write the switch statement in a proper way: https://godbolt.org/z/99MohaTMx
#include <iostream>
int main(int argc, char* argv[])
{
while (true)
{
char c{'a'};
switch (c)
{
case 'a':
std::cout << "a\n"; // forever prints "a\n"
break;
case 'b':
std::cout << "b\n";
break;
default:
break;
}
}
}
Another one, just for your current implementation, would be to use an if-else if instead of a switch.