Objective-C: the More Flexible C++
It is a surprising fact that anyone studying GNUstep or the Cocoa Framework will notice they are nearly identical to the NEXTSTEP APIs that were defined ten years ago. A decade is an eternity in the software industry. If the framework (and its programming language--Objective C) came through untouched these past ten years, there must be something special about it. And Objective-C has done more than survive; some famous games including Quake and NuclearStrike were developed using Objective-C.
Objective-C gives you the full power of a true object-oriented language with exactly one syntax addition to C and, unlike C++, about a dozen additional keywords.
Since Apple purchase Next for $400 million and Mac OS X ships with Objective-C, recycling NEXTSTEP (later called OpenStep), as well as the fact that GNUstep is delivering the rock-solid window-manager Window Maker, Objective-C is (rightly) getting more attention because it is more flexible than C++ at the cost of being slower.
In reality, Objective-C is Object C and is as close to Smalltalk as a compiled language can be. This is no surprise as Brad J. Cox added object-oriented, Smalltalk-80-based extensions to the C language.
So objective-C is a hybrid between Smalltalk and C. A string can be represented as a `char *' or as an object, whereas in Smalltalk everything is an object. As with Java (int, double,.. are no objects) this leads to faster performance.
In contrast, C++ traditionally is associated with the Simula 67 school of object-oriented programming. In C++, the static type of an object fixes what messages it can receive. In Objective-C the dynamic type of an object determines what messages it can receive. The Simula 67 format allows problems to be detected at compile time. The Smalltalk approach delays typing until runtime and therefore is more flexible.
A GNU version was written by Dennis Gladding in 1992 and then Richard Stallman took over the development. The current GNU version is derived from the version written by Kresten Thorup when he was a still a university student in 1993. He ported that version to the NeXTcube and joined NeXT.
Apple chose Objective-C for Cocoa, as NEXTSTEP was based on Objective-C. But, even if they had written it from scratch, they might have decided to use Objective-C because it is object-oriented, which is undoubtedly a must for big software projects. It extends the standard ANSI C, so that existing C programs can be adapted to use the frameworks, and programmers can chose when to stick to procedural programming and when to go the object-oriented way. C was intended to be a good language for system programming. C is fine as it allows the programmer to do exactly what she wants, all the way down to the hardware. C also keeps the gold old pointers, which can be used for efficient code.
Objective-C is simple, unambiguous and easy to learn. But most of all, it is the most dynamic language of all object-oriented languages based on C. Its dynamic late binding offers flexibility and power. Messages are not constrained by either the class of the receiver or the method selector, allowing rapid change and offering access to information about running applications.
The following is a short introduction to OOP in Objective-C, starting with the basics. Procedural programs consist of data and operations on data. OOP works at a higher level by grouping data into units, which are called objects. Several objects combined and their interactions form a program.
Abstraction is at the root of all understanding; it helps us capture the bigger image as the details are hidden. Object-Oriented Programming and the Objective-C Language (see Resources) shows the image of a clock cut half-open: what we normally see (the external view) is the interface, and the implementation (the internal workings) is hidden inside.
@interface declares a new class. It indicates the name of the class and its superclass, the protocols adhered to, the layout of the instance variables and declares the methods implemented by this class. Traditionally a class interface is stored in a file called <classname>.h.
Only externally visible methods are listed in the interface section. However, there are visibility keywords for instance variables:
@private: the instance variable is accessible only within the class that declares it.
@protected: the instance variable is accessible within the class that declares it and with the class that inherits it.
@public: the instance variable is accessible everywhere.
@implementation' defines a class. The implementation is a collection of method definitions stored in a file called <classname>.m.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
- SUSE LLC's SUSE Manager
- My +1 Sword of Productivity
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Non-Linux FOSS: Caffeine!
- Managing Linux Using Puppet
- Doing for User Space What We Did for Kernel Space
- Tech Tip: Really Simple HTTP Server with Python
- Parsing an RSS News Feed with a Bash Script
- Rogue Wave Software's Zend Server
- SuperTuxKart 0.9.2 Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide