Objective-C is an object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It was the primary programming language used by Apple for macOS and iOS development until the introduction of Swift in 2014. Objective-C combines the efficiency and performance of C with the flexibility and dynamic capabilities of Smalltalk, making it well-suited for developing applications on Apple's platforms. Its syntax and structure allow for the creation of complex applications while maintaining readability and ease of integration with other C-based languages.
Objective-C was created in the early 1980s by Brad Cox and Tom Love at Stepstone, a software company. The motivation behind its creation was to provide a more flexible programming model for developers building software for the burgeoning object-oriented paradigm. The language was developed by augmenting C with messaging capabilities similar to Smalltalk, which allowed for a more dynamic approach to programming.
In the late 1980s, NeXT Computer, founded by Steve Jobs, adopted Objective-C for its NeXTSTEP operating system, which was designed to facilitate the development of applications in a networking environment. This decision would later pay off greatly when Apple acquired NeXT in 1997, leading to Objective-C becoming the foundation for macOS and iOS development.
Despite the introduction of Swift in 2014, which was designed to be a safer and more modern replacement for Objective-C, the latter remains a significant part of Apple's ecosystem. Many legacy applications still use Objective-C, and it is supported alongside Swift in current development environments. Objective-C's dynamic runtime and messaging capabilities continue to influence the design of newer languages and frameworks.
Objective-C is fundamentally object-oriented, allowing developers to define classes, objects, and methods. This helps organize and modularize code effectively.
@interface MyClass : NSObject
- (void)myMethod;
@end
@implementation MyClass
- (void)myMethod {
NSLog(@"Hello from MyClass!");
}
@end
Objective-C allows for dynamic typing, enabling variables to hold objects of different classes at runtime, which is useful for more flexible coding patterns.
id myObject = [[MyClass alloc] init];
Instead of traditional function calls, Objective-C uses a messaging syntax that resembles Smalltalk, which allows for more dynamic method resolution.
[myObject myMethod];
Categories allow developers to add methods to existing classes without subclassing. This is particularly useful for extending third-party libraries.
@interface NSString (MyCategory)
- (NSString *)reverseString;
@end
Protocols in Objective-C are similar to interfaces in other languages, allowing for the definition of methods that can be implemented by any class.
@protocol MyProtocol
- (void)requiredMethod;
@end
Objective-C provides a property feature that simplifies the encapsulation of class variables, handling getter and setter methods automatically.
@interface MyClass : NSObject
@property (nonatomic, strong) NSString *name;
@end
The language employs both manual reference counting (MRC) and Automatic Reference Counting (ARC) to manage memory effectively.
self.name = [[NSString alloc] initWithFormat:@"Hello"];
Objective-C supports blocks, which are similar to closures in other languages and allow for inline function definition and execution.
void (^myBlock)(void) = ^{
NSLog(@"Hello from Block!");
};
Objective-C provides syntactic constructs that aid in common programming patterns, such as concise array creation and dictionary literals.
NSArray *array = @[@"One", @"Two", @"Three"];
Objective-C employs a unique error handling system using NSError, which allows methods to return errors without using exceptions.
NSError *error = nil;
BOOL success = [myObject performActionWithError:&error];
Xcode is the primary Integrated Development Environment (IDE) for Objective-C, providing a robust set of tools for development, debugging, and deployment of applications on Apple platforms. It includes a visual interface builder and extensive documentation.
Objective-C code is typically compiled using the Clang compiler, which is part of the LLVM project. Clang offers fast compilation times, great error diagnostics, and supports the latest standards of C and Objective-C.
To build a project in Xcode, developers create a new project, configure build settings, and use Interface Builder to design UI components visually. Building and running the application can be done directly within Xcode with a single button click.
Objective-C is primarily used for developing applications for macOS and iOS. It is the backbone of many legacy applications and continues to be used in combination with Swift for modern applications. Notable applications include:
When compared to relevant programming languages, Objective-C has its unique strengths and weaknesses.
For translating Objective-C to other languages, consider the following:
Existing source-to-source code translation tools for Objective-C include: