Objective-C iOS Development for Legacy & Enterprise Apps · Урок

Автоматический подсчёт ссылок (ARC)

Изучите, как ARC упрощает управление памятью и как это влияет на разработку на Objective-C и устаревший код.

«Автоматический подсчёт ссылок (ARC)» — бесплатный урок Objective-C iOS Development for Legacy & Enterprise Apps на CoddyKit. Это урок 2 из 4. Ты можешь прочитать весь урок бесплатно ниже — а потом практиковать его прямо в браузере с встроенным редактором кода и ИИ-репетитором 24/7. Это часть пути обучения Objective-C iOS Development for Legacy & Enterprise Apps, и твой прогресс синхронизируется между веб-версией и приложением CoddyKit. Курс Objective-C iOS Development for Legacy & Enterprise Apps содержит 4 уроков всего.

Части этого урока еще не переведены и отображаются на английском.

Welcome to ARC

Memory management is crucial in programming. In Objective-C, you once had to manage memory manually, which could lead to errors like memory leaks or crashes.

Automatic Reference Counting (ARC) changed this by automating a lot of the work for you. It's a compiler feature, not a runtime garbage collector.

ARC: Compiler Magic

With ARC, the Xcode compiler automatically adds the necessary memory management code (like retain, release, and autorelease calls) into your app during compilation.

This means you no longer write these calls yourself. The compiler ensures objects are kept alive as long as they're needed and released when they're not.

Your First ARC Object

Let's see ARC in action. When you create an Objective-C object, ARC automatically manages its memory. You don't need to call release.

This simple example shows an NSString being created. ARC handles its deallocation when it's no longer referenced.

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // Create an NSString object
        NSString *greeting = @"Hello, CoddyKit!";
        NSLog(@"%@", greeting);

        // ARC automatically manages the memory for 'greeting'.
        // No explicit [greeting release] is needed here.
    }
    return 0;
}

Properties & Strong References

When you declare properties for your objects, ARC uses strong references by default for Objective-C objects. A strong reference means the object is "owned" and will not be deallocated as long as there's at least one strong reference to it.

For primitive types (like int, float), you'd use assign.

#import <Foundation/Foundation.h>

@interface MyObject : NSObject
@property (strong, nonatomic) NSString *name;
- (void)sayHello;
@end

@implementation MyObject
- (void)sayHello {
    NSLog(@"Hello, my name is %@", self.name);
}
// dealloc is called automatically when strong refs are gone
- (void)dealloc {
    NSLog(@"MyObject %@ is deallocated.", self.name);
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        MyObject *obj = [[MyObject alloc] init];
        obj.name = @"Coddy"; // 'name' is a strong property
        [obj sayHello];
        // 'obj' goes out of scope, ARC releases it, dealloc is called.
    }
    return 0;
}

Custom Cleanup with `dealloc`

Under ARC, you do not call [super dealloc] or release objects within your dealloc method. The compiler handles all Objective-C object releases.

You still use dealloc to clean up non-Objective-C resources, such as Core Foundation objects, C++ objects, or file handles.

#import <Foundation/Foundation.h>

@interface MyResourceHolder : NSObject
@property (strong, nonatomic) NSString *identifier;
@end

@implementation MyResourceHolder
- (instancetype)init {
    self = [super init];
    if (self) {
        _identifier = @"My Unique ID";
        NSLog(@"MyResourceHolder %@ created.", _identifier);
        // Imagine opening a C file handle or allocating C memory here.
    }
    return self;
}

// ARC handles Objective-C objects. Use dealloc for other resources.
- (void)dealloc {
    NSLog(@"MyResourceHolder %@ deallocated. (Closing C file handle, etc.)", _identifier);
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        MyResourceHolder *holder = [[MyResourceHolder alloc] init];
        // holder goes out of scope, ARC deallocates it.
    }
    return 0;
}

Transitioning Legacy Projects

Many older Objective-C projects were written with Manual Retain-Release (MRR). Xcode provides a tool to help migrate these projects to ARC.

Go to Edit > Refactor > Convert to Objective-C ARC.... This automates much of the conversion, but manual adjustments may still be needed, especially for complex projects or mixed codebases.

Mixed Codebases

Sometimes, you might need to use non-ARC files within an ARC project (e.g., third-party libraries). Xcode allows this.

You can tell the compiler to compile specific files without ARC by setting the -fno-objc-arc compiler flag for those files in your project's Build Phases settings.

ARC & Core Foundation

ARC only manages Objective-C objects. It doesn't manage Core Foundation objects (like CFStringRef, CFArrayRef) which are C-based.

To convert between Objective-C and Core Foundation types, you use bridging casts: __bridge, __bridge_transfer, and __bridge_retained. These tell ARC how to handle ownership.

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSString *ocString = @"Hello ARC!";
        // __bridge_retained: transfer ownership from ARC to Core Foundation.
        // CFRelease must be called manually later.
        CFStringRef cfString = (__bridge_retained CFStringRef)ocString;

        NSLog(@"Objective-C String: %@", ocString);
        NSLog(@"Core Foundation String: %@", (__bridge NSString *)cfString);

        // Manual release required for Core Foundation objects obtained via __bridge_retained
        CFRelease(cfString);
    }
    return 0;
}

ARC's Limits & Pitfalls

While ARC simplifies memory management, it doesn't solve all problems. It can't prevent retain cycles, where two objects strongly reference each other, preventing either from being deallocated.

This is where weak references come in, which we'll cover in the next lesson. Also, be mindful of C-style memory (malloc/free) which ARC doesn't manage.

ARC Knowledge Check

ARC significantly changed how we manage memory in Objective-C.

Which of the following is a primary benefit of using Automatic Reference Counting (ARC) in Objective-C development?

ARC Recap & What's Next

You've learned that ARC automates memory management by inserting retain and release calls at compile time. This vastly simplifies development and reduces common memory errors.

We also touched on managing Core Foundation objects and the importance of using dealloc for non-Objective-C resource cleanup.

Next, we'll dive into Weak vs. Strong References to understand how to prevent retain cycles, a key concept even with ARC.

Часто задаваемые вопросы

Урок «Автоматический подсчёт ссылок (ARC)» бесплатный?

Да — полный текст урока «Автоматический подсчёт ссылок (ARC)» бесплатно доступен здесь в веб-версии. Чтобы практиковать его интерактивно (встроенный редактор кода и ИИ-репетитор 24/7) и разблокировать остальной курс Objective-C iOS Development for Legacy & Enterprise Apps, подпишись на CoddyKit PRO. Курс Objective-C iOS Development for Legacy & Enterprise Apps содержит 4 уроков всего.

Чему я научусь в уроке «Автоматический подсчёт ссылок (ARC)»?

Изучите, как ARC упрощает управление памятью и как это влияет на разработку на Objective-C и устаревший код. Ты практикуешь Objective-C iOS Development for Legacy & Enterprise Apps с помощью реального кода, который запускаешь прямо в браузере, и ИИ-репетитор 24/7 отвечает на твои вопросы во время урока.

Нужен ли мне опыт, чтобы начать Objective-C iOS Development for Legacy & Enterprise Apps?

Предыдущий опыт не требуется. Objective-C iOS Development for Legacy & Enterprise Apps на CoddyKit структурирован для всех уровней — от новичков до продвинутых, поэтому ты можешь начать отсюда или с самого начала и учиться в своем темпе. Это урок 2 из 4.

Сколько времени занимает урок «Автоматический подсчёт ссылок (ARC)»?

Большинство уроков CoddyKit занимают около 5–10 минут. Каждый из них компактный и интерактивный, поэтому ты постоянно делаешь прогресс и продолжаешь с того же места в веб-версии и приложении.

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Да. Каждый урок Objective-C iOS Development for Legacy & Enterprise Apps включает встроенный редактор кода, поэтому ты пишешь и запускаешь реальный код прямо в браузере и получаешь моментальную обратную связь от AI — локальная установка не требуется.

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