When should I use a struct
instead of a class? I\'m currently using classes for everything from OpenGL texture wrappers to bitmap fonts.
Is
Instead of cheaping out and referring to other questions, I'll re-iterate what others have said before I add on to them.
struct
and class
are identical in C++, the only exception being that struct
has a default access of public
, and class
has a default access of private. Performance and language feature support are identical.
Idiomatically, though, struct
is mostly used for "dumb" classes (plain-old-data). class
is used more to embody a true class.
In addition, I've also used struct
for locally defined function objects, such as:
struct something
{
something() : count(0) { }
void operator()(int value) { std::cout << value << "-" << count++ << "\n"; }
int count;
} doSomething;
std::vector<int> values;
...
std::foreach(values.begin(); values.end(); doSomething);
I like to use classes when I need to have an explicit destructor. Because then, you should be following the rule of three, in which case you need to write a copy constructer and assignment overloader. With all of this, it seems more natural to use a class than a struct.
as others have explained, they're the same thing except for default access levels.
the only reason why classes can be perceived to be slower is because a good style (but not the only one) is the one mentioned by ArmenTsirunyan: struct
for POD types, class
for full-fledged object classes. The latter ones usually include inheritance and virtual methods, hence vtables, which are slightly slower to call than straight functions.
Structs and classes in C++ as you may know differ solely by their default access level (and default accessibility of their bases: public for struct, private for class).
Some developers, including myself prefer to use structs for POD-types, that is, with C-style structs, with no virtual functions, bases etc. Structs should not have behavior - they are just a comglomerate of data put into one object.
But that is naturally a matter of style, and obviously neither is slower
1) There is no real difference between the 2 other than the fact that struct members are, by default, public where classes are private.
2) No its EXACTLY the same.
Edit: Bear in mind you can use virtual inheritance with structs. They are THAT identical :)