Protokol dan Kategori

Extending Behavior: Intro

Protocols: The Communication Contract

Defining a Protocol

@protocol MyServiceDelegate <NSObject>
@required
- (void)serviceDidFinishLoadingData:(NSArray *)data;
@optional
- (void)serviceDidStartRequest;
@end

Adopting & Implementing a Protocol

#import <Foundation/Foundation.h>

// 1. Define the delegate protocol
@protocol DataLoaderDelegate <NSObject>
- (void)dataLoader:(id)loader didFinishLoadingData:(NSString *)data;
- (void)dataLoaderDidFail:(id)loader withError:(NSError *)error;
@end

// 2. Class that uses the delegate
@interface MyDataLoader : NSObject
@property (nonatomic, weak) id<DataLoaderDelegate> delegate; // The delegate property
- (void)loadData;
@end

@implementation MyDataLoader
- (void)loadData {
    NSLog(@"DataLoader: Starting data load...");
    // Simulate network request
    NSString *result = @"Sample Data Loaded!";

    // Notify the delegate
    if ([self.delegate respondsToSelector:@selector(dataLoader:didFinishLoadingData:)]) {
        [self.delegate dataLoader:self didFinishLoadingData:result];
    }
}
@end

// 3. Class that conforms to the protocol (the delegate)
@interface MyDataConsumer : NSObject <DataLoaderDelegate> // Adopting the protocol
- (void)startConsumption;
@end

@implementation MyDataConsumer
- (void)startConsumption {
    MyDataLoader *loader = [[MyDataLoader alloc] init];
    loader.delegate = self; // Set self as the delegate
    [loader loadData];
}

#pragma mark - DataLoaderDelegate Methods
- (void)dataLoader:(id)loader didFinishLoadingData:(NSString *)data {
    NSLog(@"DataConsumer: Received data: %@", data);
}

- (void)dataLoaderDidFail:(id)loader withError:(NSError *)error {
    NSLog(@"DataConsumer: Failed with error: %@", error.localizedDescription);
}
@end

// 4. Main execution
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        MyDataConsumer *consumer = [[MyDataConsumer alloc] init];
        [consumer startConsumption];
    }
    return 0;
}

Categories: Extending Classes

Defining a Category

// NSString+MyStringAdditions.h
#import <Foundation/Foundation.h>

@interface NSString (MyStringAdditions)
- (BOOL)isEmailValid;
- (NSString *)stringByCapitalizingFirstLetter;
@end

Implementing Category Methods

#import <Foundation/Foundation.h>

// 1. Define the Category Interface
@interface NSString (MyStringAdditions)
- (NSString *)stringWithPrependedHello;
- (NSString *)stringWithAppendedExclamation;
@end

// 2. Implement the Category Methods
@implementation NSString (MyStringAdditions)
- (NSString *)stringWithPrependedHello {
    return [NSString stringWithFormat:@"Hello, %@", self];
}

- (NSString *)stringWithAppendedExclamation {
    return [NSString stringWithFormat:@"%@!", self];
}
@end

// 3. Main execution
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSString *name = @"CoddyKit";
        
        // Use category methods
        NSString *greeting = [name stringWithPrependedHello];
        NSString *excitedGreeting = [greeting stringWithAppendedExclamation];

        NSLog(@"Original: %@", name);
        NSLog(@"Greeting: %@", greeting);
        NSLog(@"Excited: %@", excitedGreeting);
    }
    return 0;
}

When to Use Protocols vs. Categories

Protocols & Inheritance

Quick Check: Protocols

Recap: Protocols & Categories