At the moment I am learning Objective-C 2. I'm aware that it's used heavily by Mac developers, but I'm more interested in learning the language at this point in time than the frameworks for developing on Mac OS X/iPhone (except for Foundation). In order to do this I want to write a few intermediate* console applications, but I'm stuck for ideas.
Most examples are something along the lines of "Write a Fraction class that has getters/setters and a print function", which isn't very challenging coming from a C++ background. I'd like some generic examples of programs, but I don't want them to include any Objective-C implementation details. I want to figure out the program structure/write my own interfaces and learn the language from there.
In summary: I am curious as to what example programs Objective-C programmers would recommend for exploring the language.
An example of an "intermediate" application would be something along the lines of "Write a program that takes a URL from the command line and returns the number of occurrences of a certain word in data returned:
example -url www.google.com -word search
"Project Euler" is a standard response for this kind of thing, but I get the feeling that you're less interested in being told to implement algorithmic stuff (since that knowledge is easier to port between languages) and more interested in miniprojects that will familiarize you with core libraries. Is this fair?
If so, IMO, you ought to know the basics of how to do the following with the standard libraries of language you hope to use for serious work:
Standard IO
Network IO
Disk IO and navigating the filesystem
Regexp utilities
Structured data (XML libraries and CSV libraries if they exist)
Programming problems I would recommend for those:
It sounds like you've already done this.
A very simple proxy - something like what you described in your post, but that listens on a port for a message containing a URL rather than taking it on the command line, and likewise returns the results to whatever contacted it over the network rather than outputting to stdio. [Obviously you need to have the machine behind an appropriate firewall for this!]
Something which takes a directory path and recursively tallies the number of lines its children contain. (So, get the directory's listing, open each child file and count the number of line breaks. Then open each of its child directories, get their listings, ...) Record any errors encountered (e.g., no read privileges) in a reasonable way. Write out the final results to file in the directory supplied.
Usually if I tool around in a language enough, I'll run across some problem which I just naturally find myself using regexps for. I'll assume the same is true for you and punt this element for now.
Fetch StackOverflow.com, and [by putting it into a DOM model and navigating that] determine whether this question is still on the front page.
I got the most out of Objective-C by exploring it with a testing framework. I have written a short blog post about it. You should also wrap your head around the memory management conventions employed by Objective-C, reference counting takes a little time to get used to but works very well if responsibilities are clearly segregated (I have written about that on my blog too).
By getting my hands dirty on a testing framework (GHUnit for that matter), I was able to learn far more about the language than I could have in a "traditional" way. Of course you'll need a little pet project, otherwise this approach doesn't make sense.
I don't think your example is a very good idea as it requires you to mess with http connections, resources etc. which is a little framework specific after all. Parsing a text file would be a little easier in this regard. Using a unit testing framework has the following advantages for you:
learn about platform specific build systems and deployment details
forced to develop components in a loosely coupled fashion from the ground up
thereby exploring unique mechanisms of the language, that might require new or make known patterns redundant (e.g. categories make dependency injection obsolete etc.)
fast compile-test cycle, less time spent in front of the debugger
combined with source control: painless experiments
You should also look into the testing framework implementation, as testing frameworks always require to work with metadata to some extend. Testing frameworks are often used together with isolation frameworks. They basically create objects at runtime that comply to certain interfaces and act as stand-ins for concrete objects. Looking at their implementation will teach you about the runtime manipulations that can be done in Objective-C (keyword: Method-Swizzling)
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I have been searching stackoverflow, Google and Reddit for about a week now and I haven't come across an answer to this question (or at least not one that I fully understand).
Just for my own amusement/education, I have been working on implementing a parser and interpreter for a scripting syntax of my own design. For the same reasons, I have been wondering if it's possible to implement the interpreter as a cross platform capable service, and expose something like an API so other applications can interface with the interpreter, and thus "bolt on" support for this new scripting syntax without having to reimplement an interpreter within themselves.
In a dream scenario, this would be possible in a completely language agnostic way so applications written in Python, C++ or Java could interface with the "black box" interpreter which may be developed in say, Python, or any other language for that matter.
I know I could probably cobble something together doing basic message passing over sockets or using pipes, perhaps, but I can't help but wonder if there's a more robust solution already in existence.
Thinking about the specifics of how the two processes would communicate, I thought something like the visitor pattern might be ideal. A brief explanation:
Say for example my scripting syntax is designed to produce three behaviors (just to keep it simple):
Do thing 1
Do thing 2
Do thing 3
But thing 1, 2 and 3 actually happen in a GUI that may be built in some other language. Within those applications, there could exist an object with its own method for things 1, 2 and 3, but it has to rely on the interpreter to know which one to do at what time. So it "accepts a visit" from the interpreter by calling the only method on the interpreter object that it knows how to call, traditionally named "accept". In turn, based on the next instruction from the script being interpreted, the interpreter responds back to the GUI object, by "visiting" do_thing_1(), do_thing_2(), or do_thing_3() on the GUI, as appropriate for the current instruction being processed.
My thoughts so far:
It does seem to me that something like dbus in Linux might do what I want, and Windows COM as well, but is there one way that works for both?
There are plenty of IPC packages out there that can expose the methods of an object in a language-agnostic way, but as things 1, 2 and 3 are dependent on the structure of the GUI, which is the application I'm NOT developing (at least not at this time, but in theory it could be written by someone else entirely), these won't work for what I'm after. I've looked at Thrift, Protocol Buffers, ZeroRPC, XPCOM, etc.
I could write an interpreter in something like C, as lots of languages have packages that provide bindings for C. I could also produce a complete interpreter in several different languages myself, as once the logic is "figured out" translating it from one language to another often isn't really that difficult, but it IS time consuming. As this is just sort of a spare-time project for my own amusement/education, I have minimal interest in going to those lengths.
I'm hoping someone more experienced than myself is going to point out some framework I haven't come across, or explain how this is achievable through one of the packages I have already looked at. Or failing that, maybe someone will be able to point out that this a stupid idea because there is some much easier way to achieve what I'm after. In either case, I would be very grateful if someone could at least put me on the right track to further educating myself.
Note: I did come across this question but it's pretty specific to Python and C++. I'm hoping for a more general solution.
I know this sounds a little bizarre, but there is a very simple application I want to write, a sort of unique image viewer, which requires some interactivity with the host system at the user level. Simplicity when developing is a must as this is a very small side project. The project does require some amount of graphical work and quite a bit of mouse based interactivity (as well as some keyboard shortcuts), but quite frankly, I don't want to dig my hands into OGL for something this small. I looked at the available options, and I think I've narrowed it down to two main choices: Webkit (through either QtWebkit or WebkitGtk), and the language Processing.
Since I haven't actually used Processing but I do have some amount of HTML5 canvas and Javascript experience, I am somewhat tempted to using a Webkit based solution. There are however, several concerns I have.
How is Webkit's support for canvas, specifically for more graphically intensive processes?
I've heard that bridging is handled better in QtWebkit than WebkitGtk. Is this still true?
To what degree can bridging actually do? Can a Webkit based application do everything that an application which interacts with the files on the system needs?
Looking at Processing, there are similarly, a couple things I'm wondering.
Processing is known for its graphical capabilities, but how capable is it for writing a general everyday desktop application?
There are many sources that link Processing to Java, both in lineage as well as in distributing applications over the web (ie: JApplets). Is the "Application Export" similarly closely integrated with Java?
As for directly comparing the two, the main concern I do have is the overhead of each. I want the application to start up as snappy as possible, and I know that Java has a bit of an overhead regarding start up because it first has to start up the interpreter. How do Processing and QtWebkit/WebkitGtk compare for start up?
Note that I am targeting the Linux platform only.
Thanks!
It's difficult to give a specific answer, because you're actually asking a few different kind of questions - and some of them you could be more precise.
Processing is a subset or child of java - it's really "just" a java framework with an free ide that hides the messy setup work of building an applet, so that a user can dive in and write something quickly without getting bogged down in widgets and ui, etc. So processing can exist by itself and the end user needs to know nothing of Java (except syntax - processing is java, so the user must learn java syntax).
But a programmer who already knows java can exploit the fun quick nature of processing and then leverage their normal java experience for whatever else is needed - everything of java is in processing, just a maybe slightly hidden (but only at first) It's also possible to import the processing.jars into an existing java program and use them there. See http://processing.org/learning/eclipse/ form more information.
"how capable is it for writing a general everyday desktop application?" - Not particularly on it's own (it's not made to be), but some things are possible and easy (i.e. file saving & loading, non-standard gui, etc.), and in some ways it's similar to old school actionscript or lingo. There is a library called controlP5 that makes gui stuff a bit easier.
Webkit is another kettle of fish, especially if you aren't making a web-based thing (it sounds like you're thinking on using the webkit libraries as part of a larger program. I'll admit I don't have the dev expertise with those specific libraries to give you the answer you really want, but I'm pretty certain that unless you have programming experience beyond html5/javascript you'll probably get going much faster with processing.
Good luck with whichever path you choose!
I have a game I wrote in Actionscript 3 I'm looking to port to iOS. The game has about 9k LOC spread across 150 classes, most of the classes are for data models, state handling and level generation all of which should be easy to port.
However, the thought of rejiggering the syntax by hand across all these files is none too appealing. Are there tools that can help me speed up this process?
I'm not looking for a magical tool here, nor am I looking for a cross compiler, I just want some help converting my source files.
I don't know of a tool, but this is the way I'd try and attack your problem if there really is a lot of (simple) code to convert. I'm sure my suggestion is not that useful on parts of the code that are very flash-specific (all the DisplayObject stuff?) and also not that useful on lots of your logic. But it would be fun to build! :-)
Partial automatic conversion should be possible, especially if the objects are just 'data containers', watch out for bringing too much as3-idiom over to objective-c though, it might not always be a good fit.
Unless you want to create your own (semi) parser for as3 you'd need some sort of a parser, apparently FlexPMD has one (never used it), and there probably are others.
After getting your hands on a parser you have to find some way of suggesting to the system what parts could be converted automatically. You could try and add rules to the parser/generator script for the general case. For more specific cases I'd use custom metadata on the actual class/property/method, assuming a real as3 parser would correctly parse those.
Now part of your work will shift from hand-converting files to hand-annotating files, but that might be ok for you.
Have the parser parse your classes and define actions based on your metadata that will determine what kind of objective-c class to generate. If you get this working it could at least get you all your classes, their simple properties and method signatures (getting the body of the methods converted might be a bit too much to ask but you could include it as a comment so you'd have a nice reference while hand-translating).
PS: if you make this into a one way process be very sure you don't need to re-generate it later - it would be bad if you find out that you have been modifying the generated code and somehow need to re-generate all those classes -- that would mean you'll have to redo all your hard work!
I've started putting a tool together to take the edge off the menial aspects of this process.
I'm trying to figure out if there's enough interest to make it clean and stable enough to release for others to use. I may just do it anyway.
http://meanwhileatthelab.blogspot.com.au/2012/08/automating-process-of-converting-as3-to.html
It's so far saving me a lot of time while porting one of my fairly large games from AS3 to objc.
Check out the Sparrow Framework. It's purported to be designed with Actionscript developers in mind, recreating classes that sort of emulate display list and things like that. You'll have to dive into some "rejiggering" for sure no matter what you do if you don't want to use the CS5 packager.
http://www.sparrow-framework.org/
even if some solution exists, note that architectural logic is DIFFERENT, and many more other details.
Anyway even if posible, You will have a strange hybrid.
I am coming back from WWDC2012, and the message is (as always..) performance anf great user experience.
So You should rewrite using a different programming model.
I am experimenting with using QTP for some webapp ui automation testing and I was wondering how people usually write their QTP tests. Do you use the object map, descriptive programming, a combination or some other way all together? Any little code example would be appreciated, Thank you
Here's my suggestion.
1) Build your test automation requirements matrix.
You can use samples from my blog
http://automation-beyond.com/2009/06/06/qa-test-automation-requirements-usability/
http://automation-beyond.com/2009/06/07/qa-test-automation-requirements-usability-2/
http://automation-beyond.com/2009/06/10/qa-test-automation-requirements-5-maintainability/
http://automation-beyond.com/2009/06/08/qa-test-automation-requirements-robustness/
http://automation-beyond.com/2009/06/09/qa-test-automation-requirements-scalability/
2) Choose your automation approach
3) Write your testing scripts according to the approach you chose
Note. QTP Repository way or Descriptive Programming belong to GUI recognition part of front-end functional test automation. They matter in terms of robustness and maintenance.
Technically, it's nearly the same. In both cases you should understand GUI recognition concept well, or you will have problems no matter the approach.
You can store GUI object recognition properties in XML-like data structure and map the record to an English-like name. Whenever the original object's properties change, you update your record in repository, while a code still refers to a mapped name.
Or you can address GUI objects by directly putting same recognition properties into a function call. Whenever the original object's properties change, you have to do code change. But you don't have to maintain extra files along with your scripts.
A good framework should support both GUI-mapped and descriptive programming notations by operating at object reference level. I.e. you should keep object recognition and object interaction tasks separate.
Note that depending on context Descriptive Programming notation may slowdown performance of your scripts and it always demands extra maintenance effort while in other cases using Object Repositories only may lead to unwanted duplication of objects' descriptions or it may limit recognition of dynamically changing GUI.
I illustrate some points made above in the following article:
A little QTP performance test: Object Repository vs. Descriptive Programming
Straight code examples (for a practical automation I recommend GUI Function Wrapping).
Descriptive programming - addressing objects by physical description properties.
Dim sProfile
sProfile = "Guest"
Set objWebParent = Browser("title:=Select Profile").Page("title:=Select Profile")
Set objWebObject = objWebParent.Link("text:="&sProfile)
boolRC = objWebObject.Exist(0)
If Not boolRC Then
'error-handling
End If
objWebObject.Click
Addressing objects by mapped GUI names
Browser("Select Profile").Page("Select Profile").Link("Guest").Click
Thank you,
Albert Gareev
http://automation-beyond.com/
I know I am late here, and you must already have what you are looking for, but I wanted to provide my inputs as well for anyone visiting this topic.
I generally never use OR, unless I encounter an environment where Descriptive Programming is a no-go. Just recently, I worked with a Mainframe Front-End GUI application that has absolutely no naming convention for objects. If you choose to use Descriptive Programming with such an application, the only way to work with its objects would be through Index or Location Ordinal Identifiers, which is not the best course of action considering 100's of objects in each pane.
So, the answer to your question really depending upon the environment and your experience with OR and DP. Most people I have worked with at my job, and on online communities prefer to work with Descriptive Programming whenever its feasible. However, I have also seen people work wonders with OR.
I have a few code samples, but, unfortunately, they are deal with Descriptive Programming. For instance, the following article talks about creating modular VBScript classes to divide application's functionality into small manageable components:
http://relevantcodes.com/qtp-using-classes-as-test-modules-i/
Similarly, this article shows how Descriptive Programming can be used to verify multiple properties of target objects through a single block of code:
http://relevantcodes.com/qtp-verify-multiple-object-properties-an-elegant-approach/
Also, a demo framework is also available for you to view here:
http://relevantcodes.com/relevantcodes1one-qtp-automation-framework/
The framework is built completely on the principles of Descriptive Programming, but in the next release, some functionality will be added that will enable users to work with ORs as well.
Thank you,
Anshoo Arora
(Thanks for linking to the original articles, Motti)
I'm playing WoW for about 2 years and I was quite curious about Lua which is used to write addons. Since what I've read so far about Lua was "fast", "light" and "this is great", I was wondering how and when to use it.
What is the typical situation where you will need to embed a script language like Lua in a system ?
When you need end users to be able to define/change the system without requiring the system to rewritten. It's used in games to allow extensions or to allow the main game engine to remain unchanged, while allow content to be changed.
Embedded scripting languages work well for storing configuration information as well. Last I checked, the Mozilla family all use JavaScript for their config information.
Next up, they are great for developing plugins. You can create a custom API to expose to the plugin developers, and the plugin developers gain a lot of freedom from having an entire language to work with.
Another is when flat files aren't expressive enough. If you want to write data driven apps where behavior is parameterized, you'll get really tired of long strings of conditionals testing for config combinations. When this happens, you're better off writing the rules AND their evaluation into your config.
This topic gets some coverage in the book Pragramtic Programmer.
Lua is:
Lightweight
Easy to integrate, even in an asynchronized environment such as a game
Easy to learn for non-programmer staff such as integrators, designers and artists
Since games usually require all those qualities, Lua is mostly used there. Other sitation could be any application that needs some scripting functionality, but developers often opt for a little more heavy weight solution such as .Net or python.
In addition to the scripting and configurability cases mentioned, I would simply state that Lua+C (or Lua+C++) is a perfect match for any software development. It allows one to make an engine/usage interface where engine is done in C/C++ and the behaviour or customization done in Lua.
OS X Cocoa has Objective-C (C and Smalltalk amalgam, where language changes by the line). I find Lua+C similar, only the language changes by a source file, which to me is a better abstraction.
The reasons why you would not want to use Lua are also noteworthy. Because it hardly has a good debugger. Then again, people hardly seem to need one either. :)
a scripting language like Lua can also be used if you have to change code (with immediate effect) while the application is running. one may not see this in wow, because as far as i remember the code is loaded at the start (and not rechecked and reloaded while running).
but think of another example: webserver and scripting language - (thankfully) you can change your php code without having to recompile apache or restart apache.
steve yegge did that thing for his own mmorpg engine powering wyvern, using jython or rhino and javascript (can't remember). he wrote the core engine in java, but the program logic in python/javascript.
the effect of this is:
he doesn't have to restart the core engine when changing the scripts, because that would disconnect all the players
he can let others do the simpler programming like defining new items and monsters without exposing all the critical code to them
sandboxing: if an error happens inside the script, you may be able to handle it gracefully without endangering the surrounding application
Rapid development for application with real-time constraints. Computer games are one of these ;-)
It's a valid solution if you want to allow third parties to develop plug-ins or mods for your software.
You could implement an API in whatever language you are using, but a script language like LUA tends to be more simple and accessible for casual developers.
In addition to all the excellent reasons mentioned by others, Embedding Lua in C is very helpful when you need to manipulate text, work with files, or just need a higher level language. Lua has lots of nifty feature (Tables, functions are first class values, lots of other good stuff). Also, while lua isn't as fast as C or C++, it's pretty quick for an interpreted language.