Free pascal for in loop code#
Free pascal for in loop free#

Free pascal for in loop code#

Actually this code should not raise an exception and just run smoothly to the second step.Ĭreating a SDL2 surface will fail intentionally because there is no bitmap file to load. If the error code indicated a failure, an exception should be raised. Create a SDL2 surface from a bitmap fileĪfter creating the renderer and window as known to you, we check for the error code (in these cases we check if one or both of them are nil).In the try-block of our code there are actually just two things tried: Hint: Sometimes SDL_GetError can be populated with a message even though functions were run successfully. Attention here, only fails will result in a message in SDL_GetError and they won’t be cleared autmatically if other functions run successully afterwards, hence you should use SDL_ClearError to clear the last error message from older functon calls. SDL_GetError returns a string (as PAnsiChar) which gives you information about the error of the last function that returned an error code which indicated failure. Most SDL2 functions return an error code which indicated success or failure. They are completely independent of Pascal’s error handling but are very useful to gather the necessary information to fix issues. SDL2 knows three error related functions: SDL_GetError, SDL_SetError(Format string, Arguments) and SDL_ClearError. After proper exception handling the program can run without termination although an exception occured.Īs you can see, here the whole whole code is encapsuled by a try. As this would terminate the program immediately, usually raised exception are caught and handled by try. In short: Pascal’s exceptions are raised by the raise keyword and stop the program flow at this point. block: // Create a window, renderer and a surface Let’s instead have a detailed look into the core part of the begin.

I will not cover this in detail here again. code block starts with the initilization of the SDL2 system and ends with the clean up part and the quitting of the SDL2 system. SDL2 function which create objects usually simply indicate failure by nil-pointers. Nearly all function in SDL2 return an error code where 0 usually means sucess and -1 usually means failure. It is called “ESDLNilPointer” and will be raised whenever a SDL2 function returns a nil pointer as error code. Right above the var block is an exception class declared whose names start by convention with a capital E instead of a capital T. As this file doesn’t exists, it will cause an exception on trying to load it (later in the code). It also has a constant “filename” which defines a file name of an imaginary file called “nofile.bmp”. The program “SDL_ErrorHandling” has three variables representing a SDL2 window, a SDL2 renderer and a SDL2 surface. Let’s start with the first part of the code: program SDL_ErrorHandling SdlSurface1 is nil on loading nofile.bmp. It will report the following exception messages:

Free pascal for in loop free#

It allows you to proceed running after the exception has been caught to free resources and prevent memory leaks.

It will return several helpful information to make identification of the cause of the exception easier. If you run this program, it will stop execution because it catches an exception. If Assigned(sdlWindow1) then SDL_DestroyWindow(sdlWindow1)

If Assigned(sdlRenderer) then SDL_DestroyRenderer(sdlRenderer) If Assigned(sdlSurface1) then SDL_FreeSurface(sdlSurface1) WriteLn('Exception ESDLNilPointer: ' + sLineBreak + E.Message) SdlSurface1 := SDL_LoadBMP(filename) // sdlSurface1 will be nil! SDL_CreateWindowAndRenderer(500, 500, not Assigned(sdlWindow1) then Create a window, renderer and a surface If SDL_Init(SDL_INIT_VIDEO) < 0 then Exit Let’s look at the whole program code: program SDL_ErrorHandling įilename = 'nofile.bmp' // this file does not exist Both worlds can be combined and this chapter shows you how. Error handling in Pascal means raising exceptions and catching them.