• dog2002 (11/11) Jan 28 2021 I saw these functions in some projects. For example: in Dagon
• frame (7/18) Jan 28 2021 Not 100% sure what you mean but I guess you ask how to implement
• frame (28/34) Jan 28 2021 A very simple example:
• dog2002 (2/31) Jan 28 2021 Thank you, I'll try it

dog2002 <742617000027 aaathats3as.com> writes:

I saw these functions in some projects. For example: in Dagon 
(https://gecko0307.github.io/dagon/) there are functions like 
onKeyDown. This function doesn't need to call - it checks pressed 
keys every time. Or Update in Unity (game engine). It doesn't 
need to call, but it executes itself every frame.

Okay, maybe it sounds confusing. I just want to understand how to 
implement functions that wait for events and execute code inside 
the function. Something like this:

void onKeyPressed(int key) {
     //the code to be executed if a key has been pressed
}

frame <frame86 live.com> writes:

On Thursday, 28 January 2021 at 17:10:57 UTC, dog2002 wrote:
 I saw these functions in some projects. For example: in Dagon 
 (https://gecko0307.github.io/dagon/) there are functions like 
 onKeyDown. This function doesn't need to call - it checks 
 pressed keys every time. Or Update in Unity (game engine). It 
 doesn't need to call, but it executes itself every frame.

 Okay, maybe it sounds confusing. I just want to understand how 
 to implement functions that wait for events and execute code 
 inside the function. Something like this:

 void onKeyPressed(int key) {
     //the code to be executed if a key has been pressed
 }

Not 100% sure what you mean but I guess you ask how to implement 
a handler? If an event occurs, a routine decides to call your 
onKeyPressed function and pass the keyCode which was pressed. The 
routine must be registered on a event source that will emit the 
events. The routine is basically just a callback and that is 
indeed called every frame again if an event occurs.

frame <frame86 live.com> writes:

On Thursday, 28 January 2021 at 18:27:09 UTC, frame wrote:

 Not 100% sure what you mean but I guess you ask how to 
 implement a handler? If an event occurs, a routine decides to 
 call your onKeyPressed function and pass the keyCode which was 
 pressed. The routine must be registered on a event source that 
 will emit the events. The routine is basically just a callback 
 and that is indeed called every frame again if an event occurs.

A very simple example:

bool myEventA = true;
bool myEventB = false;

// event source that generates the event (must be called to run)
void source() {
     observe(myEventA);
}

// routine that decides what handler to call
void observe(bool event) {
     switch (event) {
     case true:
         onMyEventA(event);
         break;

     case false:
         onMyEventB(event);
         break;

     default:
         assert(0);
     }
}

// handler
void onMyEventA(bool event) {
     // do something
}

void onMyEventB(bool event) {
     // do something
}

dog2002 <742617000027 aaathats3as.com> writes:

On Thursday, 28 January 2021 at 18:56:15 UTC, frame wrote:
 On Thursday, 28 January 2021 at 18:27:09 UTC, frame wrote:

 [...]

 A very simple example:

 bool myEventA = true;
 bool myEventB = false;

 // event source that generates the event (must be called to run)
 void source() {
     observe(myEventA);
 }

 // routine that decides what handler to call
 void observe(bool event) {
     switch (event) {
     case true:
         onMyEventA(event);
         break;

     case false:
         onMyEventB(event);
         break;

     default:
         assert(0);
     }
 }

 // handler
 void onMyEventA(bool event) {
     // do something
 }

 void onMyEventB(bool event) {
     // do something
 }

Thank you, I'll try it