Is Objective-C++ a totally different language from Objective-C?

Question

As the title says... are they considered different languages? For example if you've written an application using a combination of C++ and Objective-C++ would you consider it to have been written in C++ and Objective-C, C++ and Objective-C++ or all three?

Obviously C and C++ are different languages even though C++ and C are directly compatible, how is the situation with Objective-C++ and Objective-C?

Answer 1

From: https://en.wikipedia.org/wiki/Objective-C#Objective-C.2B.2B

Objective-C++ is a front-end to the GNU Compiler Collection, which can compile source files which use a combination of C++ and Objective-C syntax. Objective-C++ adds to C++ the extensions Objective-C adds to C. As nothing is done to unify the semantics behind the various language features, certain restrictions apply:

• A C++ class cannot derive from an Objective-C class and vice versa.
• C++ namespaces cannot be declared inside an Objective-C declaration.
• Objective-C classes cannot have instance variables of C++ classes which do not have a default constructor or which have one or more virtual methods, but pointers to C++ objects can be used as instance variables without restriction (allocate them with new in the -init method).
• C++ "by value" semantics cannot be applied to Objective-C objects, which are only accessible through pointers.
• An Objective-C declaration cannot be within a C++ template declaration and vice versa. However, Objective-C types, (eg, Classname *) can be used as C++ template parameters. Objective-C and C++ exception handling is distinct; the handlers of each cannot handle exceptions of the other type.
• Care must be taken since the destructor calling conventions of Objective-C and C++'s exception run-time models do not match (ie, a C++ destructor will not be called when an Objective-C exception exits the C++ object's scope). The new 64-bit runtime resolves this by introducing interoperability with C++ exceptions in this sense

Answer 2

Objective-C++ simply allows Objective-C and C++ code to be mixed (with caveats). It's not really a language on its own so much as a mechanism for allowing the two languages to intermix.

Answer 3

C and C++ are not directly compatible. Neither is a superset of the other (though most C is valid C++). Objective-C is a strict superset of C, and Objective-C++ is a strict superset of C++. Those are the only statements you can make (except trivially reversing it).

Answer 4

At first glance, using the Objective-C++ dialect looks like a straightforward approach. It is the result of mashing C++ and Objective-C together in the same compiler, and robust implementations exist in GCC and now clang. Considering just how different the details of Objective-C and C++ are, the GCC hackers have done a great job of it. But as you start renaming your .m files to .mm to introduce chunks of C++, you quickly realise it's not quite so simple.

Header files and the C preprocessor in general have caused headaches for C, C++ and Objective-C programmers for decades. It gets worse when you try to mix the languages. Say you wanted to use the STL's map in an Objective-C class in your project. Apple's Foundation libraries to my knowledge don't contain a sorted, tree-based map; one of our StyleKit Components needs exactly that, for example. So we simply create an instance variable for the map in our class and away we go:

#include <map>
@interface MyClass : NSObject {
 @private
 std::map<int, id> lookupTable;
} 
 // ...
@end

However, std::map [2] only makes sense to a C++-aware compiler, and only after an #include [3], so this header now can only be #imported from Objective-C++ files. Any code using this class now needs to be converted to Objective-C++ itself, and importing from other headers leads to a cascade effect that quickly encompasses the whole project.

In some cases, this may be acceptable. However, switching a whole project or large parts of it across just to introduce a library which is used in one location is not only excessive; if you're the only one who knows C++ on a project with multiple Objective-C programmers, you might find this to be an unpopular idea. It might also cause issues in the same way that compiling pure C code with a C++ compiler rarely is completely hassle-free. Moreover, it means that code isn't automatically reusable in other Objective-C projects.

So it's always better not to mix up unless it's so important

To know more about strategies for using objective c++ in objective c and vice versa click here

Answer 5

It's hard to answer this question confidently without understanding what definition of "different language" you want to apply.

Objective-C is a superset of C: it adds some additional syntax on top of the C language. Objective-C++ is a superset of C++ in the same way.

C and C++ are actually different languages. Although C++ is designed to be compatible, there is some C that is not valid C++, and vice versa.

So, I'd say, yes, Objective-C++ is a different language from Objective-C, because C++ is a different language from C. However, I wouldn't call them totally different.

Answer 6

Objective-C is probably the official term that you would put in a resume.

Objective-C++ is not really a new language, it just specifies a few things that allow Objective-C code to co-exist with C++ code. Saying your app was written in Objective-C and C++ or just Objective-C++ is probably what you want. Putting all of Objective-C, Objective-C++, C++ is redundant.