Function names that are pointers whaaaaa?

[JaxDragon]

I was randomly looking at Lazy Foo's tuts, and I noticed his load_image function is a pointer.

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SDL_Surface *load_image

What I don't understand is, why would you make a function itself a pointer? Keep in mind I have a basic understanding of C++(I thought I understood pointers quite well, but apparently not).

My guess is that hes assuming you will be using that function inside another function

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funcFunction(&load_image) //Doesnt quite make sense

or its the equivalent of this:

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SDL_Surface load_image(std::string *filename )

or maybe it can be used like this

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void *pointerFunc(int x, int y)

to translate into this

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void pointerFunc(int *x, int *y)

Also, I have no idea what/how to use STL, so if it is indeed STL, let me know and I'll find out my answer when I get sams C++ in 21 days.

[Joeyotrevor]

Actually, this

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SDL_Surface *load_image()

means the function returns a pointer to a SDL_Surface. It can also be written

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SDL_Surface* load_image()

or

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SDL_Surface * load_image()

The asterisk can be anywhere between the type and the name when using pointers.


A function pointer is declared as

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returnType (*functionPointer)(paramType param1, paramType param2);

You can set them to point to functions like so:

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functionPointer = &myFunc;

and call the function they point to like this:

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functionPointer();

Function pointers are rarely used in OOP C++ thanks to polymorphism and virtual functions.

[JaxDragon]

Oh ok, now I understand.

[Falco Girgis]

Keep in mind that a function itself is stored somewhere in memory just as variables are. So doing this:

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&myFunction

is referring to the memory address of the function.

[trufun202]

Simply put, function pointers are badass, and damn useful.

I actually use function pointers (aka delegates in .NET) in my Snowcone Stand game. I explain this briefly in my latest video.

But, essentially I'm using function pointers to give a Button it's "OnClick" behavior without having to define it directly in the Button class. Since a button can be reused on several forms, you wouldn't want to hardcode the "OnClick" behavior. Instead, the function is defined outside of the Button class and a reference is passed in. This keeps the Button class clean and flexible.

EDIT: clean and flexible...just how I like my women.

[K-Bal]

But, essentially I'm using function pointers to give a Button it's "OnClick" behavior without having to define it directly in the Button class. Since a button can be reused on several forms, you wouldn't want to hardcode the "OnClick" behavior. Instead, the function is defined outside of the Button class and a reference is passed in. This keeps the Button class clean and flexible.

You should give boost::signals a try :D

[trufun202]

You should give boost::signals a try :D

Sweet, that will handy when I get to menus and UI for Golvellius, which is built in C++.

.NET actually has an event system built into it. Broadcasting an "OnClick" event is really more customary, but since all of my controls are sharing the same interface, I found it to be cleaner to use delegates.

[avansc]

has anyone mentioned threading? dont think you can do those without function pointers.

[trufun202]

has anyone mentioned threading? dont think you can do those without function pointers.

yep, that's true. Same goes for asynchronous callbacks.