I am new to Objective-C and I am wondering if it is possible to mix C and pure Objective-C freely. If so, does it have any effects on my program?
Objective-C is a strict superset of C thus C code is a subset of Objective-C code so all C code is also Objective-C code.
Thus you can include any C code in Objective-C.
Related
How could it be possible to call D functions from Objective C? Is such a bridge even possible?
D has limited Objective-C support already: https://dlang.org/spec/objc_interface.html
This thread explains how to do the same from C++: Calling a D function directly from C++
I guess it should not be difficult to do the same from Objective-C code.
Since Objective-C still has all the C stuff, they could call each others functions through the extern(C) interface too, reducing the problem to the solved issue of calling D functions from C.
I am little confused finding C style syntax in an Objective-C project (for example below syntax is not how method are defined in Objective-C, by the book). I am clear that this works since the code I have compiles without errors - but I am not sure how and why, this code is regular Objective-C .h,.m files. Can someone explain how this fits in?
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
//use of round brackets
void drawLinearGradient(CGContextRef context, CGRect rect, CGColorRef startColor,
CGColorRef endColor);
// C style syntax for passing params
Also this is very specific around the Core Graphics code that I have seen so far, is it allowed to write regular Objective-C methods like this also or only files with CG code...?
Objective-C is just a superset of C, in the same way as C++. (Both were originally implemented as preprocessors that convert the code to straight C code.) Objective-C method calls are translated to calls to the C function objc_msgSend() (and its variants) and it's possible (though tedious) to call it directly.
The gory details are spelled out here:
https://developer.apple.com/library/ios/#documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html
Core Graphics is a C API, not Objective-C. Since Objective-C is a superset of C, any valid C code will compile just fine in .m files.
Objective-C is a superset of C, so you can define plain old C functions in a .m file, and you can call plain old C functions in a .m file using the normal C syntax.
The CGColorSpaceCreateDeviceRGB function is a plain old C function. It is part of the Core Graphics framework (also known as Quartz 2D), which has a pure C API - the API only uses plain C, not Objective-C.
You cannot define Objective-C object methods using plain old C function syntax - you must use Objective-C method syntax. And you should not try to send messages to Objective-C objects using plain old C syntax - you should use the Objective-C message sending syntax (the square brackets).
objc supports standard C that why you find c code in objc project.
As for the framework provided by Apple, if it has coreprefix,like CG standing for core graphic, it usually means it is written in C.
Since Objective-C is basically an extension of C, Does the code get converted to pure C code before it is compiled to native code ?
If so, does the conversion happens on RAM or a temporary file containing C code on disk is created by the compiler which is further compiled by C compiler to native code ?
That Objective-C syntax is an extension of C syntax does not mean that it could not have its own compiler. C++ is the same way - its syntax is compatible with C (for the most part, anyway) but it has its own set of tools. Compilers for C, C++, and Objective-C can reuse parts of each other for preprocessing, syntactic analysis and code generation, but there is not need to run them sequentially (e.g. Objective-C ==> C ==> Target code). Compilers no longer go through human-readable assembly language, either (this has been the case for a very long time, too).
No, Objective-C gets compiled to assembler directly (assuming GCC).
I'm trying to make a Lua compiler for Mac OSX with an interface written in Objective-C and the Lua source code written in C.
You already are combining C and Objective C. No extra effort is needed.
Objective-C is a proper superset of C. Any C you write in an Objective-C file is perfectly valid.
Do all functions (as opposed to class/instance methods) in Objective-C use C syntax for both declaration and calling?
well, it really is C. Objective-C is a superset of C, meaning that you can use any C construct you want and the compiler will handle it. Just declare C functions as you normally would, and call them as you normally would.
Yes, they do. Objective-C is built on top of C, so the C syntax is valid.