I believe i can learn thing or two if i can see the implementation files (.m files). Is there any way the i can view NSString.m or NSNumber.m files? and others? If i try to find these files using spotlight, i get nothing.
No, most (all?) of the Cocoa library implementations are only distributed in a compiled binary form. You could disassemble them, but that's probably against the Mac OS X EULA, and it also wouldn't help you understand them at all.
You could take a look at Cocotron, which is an open-source implementation of Cocoa. It won't be exactly the same, but at least for the core classes, it will be virtually identical.
Many of the basic cocoa classes, like NSString and NSNumber, are implemented in core foundation and "toll-free bridged" to objective-c classes. Core foundation is a C (not ObjC) API and the source is available as part of the Darwin open-source project.
So, to see how NSString or NSNumber is implemented under the hood, follow the link above and take a look at CFString and CFNumber, respectively (you'll need an Apple developer account, but registration is free).
Also worth looking at the mySTEP sources.
This helped me when doing something that subclassed NSMatrix some time ago.
I would guess they are already compiled into libraries.
I just did a quick check on my mac and could not find a NSString.m file as well. Are you utilizing Xcode's documentation? I find it has most everything I need.
Related
This question pops up quite often here, even if just implicitly when users mistag their iOS questions. So, what’s the difference between Xcode, Objective-C and Cocoa?
Objective-C is a programming language. It could be said that it’s just a description of what valid Objective-C programs look like and what they mean. If you have a source code listing written in Objective-C, you need an interpreter or a compiler to put the listing to work. Languages like Objective-C are usually compiled, so most people use a compiler (like LLVM). Objective-C is almost exclusively used to develop for iOS and OS X, but there are other uses, too – as an example, some people write Objective-C for Linux.
You can use a text editor to write the sources and a compiler to turn them into an actual programs, but with modern technologies there’s much more to take care of, so that there is another program to make your job easier. These are called Integrated Development Environments, or IDEs. An IDE offers you a convenient way to edit the sources, compile them, debug the resulting programs, read the documentation, and many other things. Xcode is one such IDE. An important observation here is that Xcode does not compile your sources itself, it just calls the standalone compiler (LLVM). And Xcode is not the only IDE you can use to develop Objective-C apps – there’s AppCode, for example.
Writing iOS or OS X apps from scratch each time would be very time-consuming. That’s why Apple provides the developers with a good set of libraries. The libraries are simply a huge amount of source code written by Apple, and this source code takes care of most things that apps have in common. These libraries are called Cocoa.
Now, if you can’t figure out how to extend a class, you are most probably talking about Objective-C. It doesn’t have anything to do with Xcode or Cocoa, you could be very well writing some GNUstep code for Linux using Vim as an IDE and GCC as a compiler. On the other hand, if your Xcode build process fails because of some mysterious setting, or if you’re trying to build a static library in Xcode, that’s clearly an Xcode issue. And if you can’t figure out how to use some NSObject facility or the NSFileManager class, that’s Cocoa. (But it doesn’t have to be Xcode-related, as you could use AppCode or TextMate as your IDE!)
Originally available on my blog. Feel free to link to the blog post or this question when retagging or explaining the difference.
Xcode is the integrated development environment (IDE)—the application—that developers use to write software for iOS and/or OS X. It includes the editor, the build system (determining what to build to produce the desired target), and quite a few other things.
Objective-C is the main language that developers write such software in. They may write bits of it in pure C, use C++ or combine it with Objective-C (producing Objective-C++), or write some or all of the program in another language entirely, such as MacRuby, Java (with j2objc), or C# (with MonoTouch).
Xcode includes the Clang compiler, which turns code written in Objective-C, C, and a few other languages into executable code. Most error messages come from Clang, and Xcode relies heavily on it for search indexing, syntax highlighting, and name completion of Objective-C code.
Cocoa and Cocoa Touch are application frameworks. Each one is a suite of many individual frameworks (libraries stored in folders named blahblah.framework), such as:
Foundation (both): General object-oriented utilities, including NSString, NSURL, NSFileManager, etc.
Core Foundation (both): Mostly the same thing, but different, mainly in having a C-based API rather than Objective-C
Application Kit (Mac): Application and windowing framework
UIKit (iOS): Application and windowing framework
Core Graphics (both): Drawing
Core Animation (both): Sprite-management and animation framework
(and many, many more where they came from, especially on the Mac)
So:
You can use a framework besides Cocoa or Cocoa Touch, but you'll have to have some Cocoa/Cocoa Touch code, at some level, in order for your application to talk to the system, receive events, draw, etc. Frameworks that specifically target Mac and/or iOS will include the relevant wrappers for you, at varying levels of quality.
You can use a language besides Objective-C, but you'll have lots of syntactic awkwardness, as most of Cocoa and Cocoa Touch are designed for Objective-C's unique syntactic features (particularly selectors).
You can use an editor besides Xcode, and you can even use a build system besides Xcode (such as make), but Apple's App Stores expect apps built a particular way (especially with regard to code signing), so unless you're not targeting the App Stores, any other build system has to replicate what Xcode does or risk its users getting rejections.
A clear mistake is failing to differentiate Xcode from everything else. Xcode is the tool you are using to program in - to edit code, run code, etc. So if you are having trouble with the tool (e.g., the window doesn't show you your code properly, or you're having trouble drawing your interface, etc.), that's an Xcode problem.
If you don't understand why your code doesn't work, you're probably having an Objective-C problem or a Cocoa problem. But you won't necessarily know which.
It's an Objective-C problem if the root of your trouble is that you don't know how the language works (e.g. you don't know what the asterisk is for, or that declaration is not instantiation, or that messages to nil do not error out but don't do anything either).
It's a Cocoa problem if you don't grasp the delegate architecture or how a view controller works.
But my experience of the way people pose questions is that you may be ignorant of which of these you are ignorant of. I don't mean you personally, I mean all of us. This can make it difficult to pose the question properly because you don't know what exactly it is that you don't know — if you did, you'd know it and you probably wouldn't be having a problem (you'd be fixing the problem and on to the next thing).
Are there frameworks/generators for producing iOS code from any other language?
A dynamic language like JavaScript, ruby or Python are preferred. Googling for iOS code generators was largely fruitless.
The problem with systems like PhoneGap is that their output is a full-fledged application. What I need to produce is a library (.a & .h file eventually) that other Objective-C developers can reuse in their projects.
RubyMotion may or may not do what you want. I haven't seen much about the practicalities of it yet, but I'm thinking since it's statically compiled chances are good that it can produce libraries that can be simply linked into Objective-C projects. One might need another tool to produce the header files.
Of course, this is all speculation.
I think the best solution for what you're looking for is Titanium. It has its own sdk (in JavaScript), a complete IDE and allows you to have one codebase for all major platforms (iOS, Android included). What it's really awesome is the fact that it actually generates native code (a valid XCode project or a Java one for Android). It's also free and open source. Definetely worth a look.
I've never seen code generators, but there are a variety of "spoofs" as it were.
http://xamarin.com/monotouch - iOS on C#
http://phonegap.com/ - iOS on HTML, CSS , Javascript
http://ipodtoucher55.blogspot.com/2010/06/how-to-create-iphone-apps-in-flash-cs5.html - one of several tutorials for flash on iOS
I've seen links to python libraries and I think java too.
When it comes down to it though, they're all work arounds, not direct development.
I am writing a Mac OS X desktop application in which I want to be able to parse fragments of Objective-C such as variable and method declarations, as well as full Objective-C header and source files.
It looks to me as if I should be making use of Clang to do this, but I could do with some pointers and examples on how to integrate it as a library in my project, and how to invoke it to parse strings and files.
Can anyone provide me with any help on this?
You probably want libclang, code browsable at http://llvm.org/svn/llvm-project/cfe/trunk/tools/libclang/ (though you'll need to checkout the entire Clang repo to build it). There's very little documentation around on it, sadly. There is a presentation at http://llvm.org/devmtg/2010-11/Gregor-libclang.pdf that might help kickstart things, but mostly just some hunting through the code is the way to go.
Clang is actually more modular than libclang provides for (you can import just the components you want). If you've adventurous, there are examples at http://llvm.org/svn/llvm-project/cfe/trunk/examples/.
It seems that Cocoa seems to be the main platform for Objective-C. GCC (which Xcode uses) supports Objective-C so it must be available on a wide range of platforms.
Are there any notable cross-platform projects that use Objective-C but not Cocoa (or its open source cousin GNUStep)? Is it really used outside the Apple ecosystem?
Objective-C has also been popular in the scientific and financial services communities. There are still many Objective-C based applications deployed in banking, mostly on the trading analysis front. A friend works on a nearly million line of code Objective-C based analysis and trading engine for which they have written their own class hierarchy from scratch.
At one point, one of the more popular Linux window managers was written in Objective-C. That was a few years ago and may no longer be the case.
The LLVM compiler also compiles Objective-C, including having full support for Blocks. It is quite portable, too.
There is also David Stes's Portable Object Compiler. It compiles Objective-C to C and uses a class hierarchy that is based quite directly upon the original ICPak class hierarchy from StepStone.
It seems what you're asking is if Objective-C is ever used without Cocoa, or GNUstep, or Cocotron, or any API like them.
The answer is basically no. Without an API like Cocoa (or GNUstep, etc.), Objective-C isn't very useful. For example, without NSObject, retain and release wouldn't even exist. A ton of very important features are built into these APIs, so it's somewhat pointless to use Obj-C without one of them.
Yep, there sure are. The one I can think of from the top of my head is Cocotron. An effort to port AppKit to Windows.
http://www.cocotron.org/
Aside from that, Objective-C can be used on any platform that gcc will run on. You won't have the wealth of frameworks that are available in Cocoa on OS X or the iPhone, although as you mentioned, GNUStep does a pretty good effort.
Super-newbie question!
I've been looking for a list of all the classes that come with Objective-C and Cocoa but can't seem to find one.
Hoping that it has matching methods and syntax(?) as well.
Be gentle with me!
Thanks,
Spencer.
I would start here: http://developer.apple.com/referencelibrary/Cocoa/index.html
The system is broken up into frameworks, so you will not find a single listing. It depends on which frameworks you include with your project. good luck.
If you're using XCode, there's a documentation browser (Help -> Documentation) that's searchable. If you want to browse by classes you can also do so here. You might need to subscribe or download the documentation first though.
I'm finding this very convenient for iPhone development at least, since I can just type in a class or method name and get its documentation very quickly. YMMV for Mac OS X documentation though since I haven't used that at all.