I would like to do this:
Passing function name as parameter, C++
But the given example doesn’t work in OpenFrameworks
Any thoughts?
S
Could you post the code that doesn’t work? OF is just C++ so you can pass pointers to functions around if you want to.
Sure
void ofApp::myOtherFunction() {
cout << endl << "And this is the result.";
}
void ofApp::myFunction(void (*otherFunction)(), char parameter[80]) {
cout << parameter;
(*otherFunction)();
}
and in draw()
myFunction(&ofApp::myOtherFunction, "I am calling a function with a function.");
calls a types error
… you are declaring a function that takes… a normal function
and you are passing a function that is declared within a class
you need to change one of two…
easiest will be 2 declare your func outside ofApp.
hi,
sorry I don’t immediately understand this (probably being dim)
please can you explain in a little more detail?
Ahhh
I geddit
I was being dim, apologies
no problem
the syntax for passing a member func is this
void myFunction(void (ofApp::*otherFunction)()) {
(this->*otherFunction)();
}
keep in mind that passing member functions to other classes , sometimes means that you need to pass the class * as well…
so unless there is no other way around it just pass the class… no need to complicate things when they can be simple
well, i have it working fine as long as I drop the definitions out of ofApp, and then:
void myOtherFunction() {
cout << endl << "And this is the result.";
}
void myFunction(void (*otherFunction)(), char parameter[80]) {
cout << parameter;
(*otherFunction)();
}
in draw
myFunction(&myOtherFunction, "I am calling a function with a function.");
But that leads me to two questions
-
are you explaining how to have it working with the definitions within ofApp in your post above? If so, I can’t get this approach working, please can you clarify?
-
if the function in ‘myOtherFunction’ requires a parameter defined in the course of ‘myFunction’, how do I pass this to it? for example, out<<(i) where i is an int defined in myFunction.
Fingers crossed
a good way to figure this out is to study the ofSort() functions in openFrameworks
the example I gave you is very basic just to get the logic - it is better to use generic member functions with templates , otherwise, by being too specific you are not achieving anything
template<class drawClass> void draw(drawClass * drawC){ drawC->draw(); }myrenderer->draw(this)
myrenderer->draw(&rect);
myrenderer->draw(&circle);
myrenderer->draw(&whateverClassAsLongAsItHasADrawFuncInIT);
//now with member functions directly
template<class c_l_a_s_s> void draw(void (c_l_a_s_s::*otherFunction)()=NULL) { void (c_l_a_s_s::*renderer)() ; c_l_a_s_s * t; renderer= otherFunction; (t->*renderer)(); }
implementation
renderer->(&whateverClass::whateverfunction)
there is everything you need to know about this
here:
http://www.newty.de/fpt/fpt.html#defi
hope this makes sense… I think it is one of those things that once you grasp it you will see just how easy this is and use it all the time…
some things just take a while…
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hmmm, I’m trying to get my head round it and struggling!
Are there any working examples that I can pick apart?
secWin.zip (48.8 KB)
maybe it is your compiler settings not allowing this…?
I’ve made an example of creating a second OF window, and doing
secWin.draw(&ofApp::draw2);
this works both on mac and winCB
I mean, if you are looking for a 100% working example, look inside OF / lib/ of/utils/ofUtils.h
ok, fab, I get this so far - have stripped down the example to the very basics:
doSomething.zip (57.8 KB)
One question - at the minute the ‘doThis’ function passes an int along with the ‘functionToSend’
But how do I pass that int to be used in ‘functionToSend’ as it operates? For instance, setting the rectangle width?
yes I owe you a few 
If you look at my other thread, parallel computing, you’ll see why I wanted to do it… very happy to finally have sorted that one
many thanks!
S
Hey igiso
Wondering if you can give me another helpful pointer
As I mentioned, I used the above to wrap some parallelising (grand central dispatch) code into single function lines. Nice and tidy, or so I thought. It works well for running simple tasks concurrently…
But (always a but!) when I try to replace the simple task with some form or operation on a vector array and keep the single function line approach, I get a crash.
Do you know what might be causing this? Since I posted here yesterday I’ve adapted the sketch to test it a bit further and this shows that the problem is not apparently the concurrency code itself (as I thought yesterday). When I separate this out from being wrapped up into a single line everything runs just fine. So I’m presuming that the issue is in how I am doing the ‘wrapping’, right?
Hope you can help - here’s a zip file which includes commenting to explain the problem more clearly: concurrency2.zip (73.1 KB)
Sam
you need to share its guts as well…
you just passed the function, (scope) not the
class scope pointer…
can you make your targets global ?
remove them from ofapp class
and paste this above ofApp:
extern vector <int> targets;
vector <int> targets;
its either that or pass a this, and access the functions from there…
the compiler uses different part of the memory to save this now so it should work…
but I don’t know if it can benefit you in your actual app.
I should clarify what I mean by “passing this”:
(without externs)
concurrency.zip (79.8 KB)
template<class c_l_a_s_s>
void for_all(c_l_a_s_s * doTask,void (c_l_a_s_s::*otherFunction)(int), int start, int end) {
void (c_l_a_s_s::*with)(int) ;
with = otherFunction;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_apply(end-start, queue, ^(size_t blockIdx) {
int i = start+blockIdx;
(doTask->*with)(i);
});}
so in your app you do:
parallelise.for_all(this,&ofApp::functionA, 10,20);
now *doTask actually means something instead of being just an empty reference…
Gah, I get it now. That simples!
Many thanks again
S
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