jacob9706
17-12-2012, 17:11
Hi everyone,
Today I will be showing you how to implement an easy autonomous system based on callbacks/events. If anyone has done JavaScript using the jQuery library you will be quite familiar with the concept of a callback. A callback is a function (or method depending on the language) that executes after a set of code is done running.
Here is a quick jQuery example...
$(document).load(loadFunction);
var loadFunction = function() {
alert(“Loaded”);
}
What we will be doing today will be a little bit different. We will be creating a “list” of actions we want to preform one after another. This list will be represented as a vector of functions. The first thing we have to do is define a function pointer that returns a boolean and has nothing as its paramaters.
typedef bool (Event*)(void);
That line defines a function pointer called Event that takes nothing(void) and returns a boolean(bool).
The next step will be to define a function that will execute all of our function pointers called Event.
// Function that takes a vector of Even
bool runStringOfEvents(std::vector<Event> events)
{
// Loop through every event
for (unsigned int i = 0 i < events.size(); i++)
{
// Get current event from vector
Event event = events.at(i);
// Execute the event and get the return value
bool success = event();
// If it failed return false
if (!success)
{
return false;
}
}
// If all succeeded return true
return true;
}
Now that the hard part is done we can create a function we will call two times through a list of events we pass to our runStringOfEvents function.
bool someEvent()
{
std::cout << “Event executed” << std::endl;
return true;
}
Now that we have our event function we can create a list in our program and execute the list of events.
int main(int argc, char** argv)
{
// Create the vector to hold our events
std::vector<Event> events;
// Add the function to the list twice
events.push_back(&someEvent);
events.push_back(&someEvent);
// Run the events
runStringOfEvens(events);
}
Today I will be showing you how to implement an easy autonomous system based on callbacks/events. If anyone has done JavaScript using the jQuery library you will be quite familiar with the concept of a callback. A callback is a function (or method depending on the language) that executes after a set of code is done running.
Here is a quick jQuery example...
$(document).load(loadFunction);
var loadFunction = function() {
alert(“Loaded”);
}
What we will be doing today will be a little bit different. We will be creating a “list” of actions we want to preform one after another. This list will be represented as a vector of functions. The first thing we have to do is define a function pointer that returns a boolean and has nothing as its paramaters.
typedef bool (Event*)(void);
That line defines a function pointer called Event that takes nothing(void) and returns a boolean(bool).
The next step will be to define a function that will execute all of our function pointers called Event.
// Function that takes a vector of Even
bool runStringOfEvents(std::vector<Event> events)
{
// Loop through every event
for (unsigned int i = 0 i < events.size(); i++)
{
// Get current event from vector
Event event = events.at(i);
// Execute the event and get the return value
bool success = event();
// If it failed return false
if (!success)
{
return false;
}
}
// If all succeeded return true
return true;
}
Now that the hard part is done we can create a function we will call two times through a list of events we pass to our runStringOfEvents function.
bool someEvent()
{
std::cout << “Event executed” << std::endl;
return true;
}
Now that we have our event function we can create a list in our program and execute the list of events.
int main(int argc, char** argv)
{
// Create the vector to hold our events
std::vector<Event> events;
// Add the function to the list twice
events.push_back(&someEvent);
events.push_back(&someEvent);
// Run the events
runStringOfEvens(events);
}