Refactoring Legacy Objective-C

Why Refactor Legacy Objective-C?

Spotting Code Smells

Refactor: Extract Method

#import <Foundation/Foundation.h>

@interface ReportGenerator : NSObject
- (void)generateDetailedReportForData:(NSArray<NSNumber *> *)data values:(NSArray<NSNumber *> *)values;
@end

@implementation ReportGenerator
- (void)generateDetailedReportForData:(NSArray<NSNumber *> *)data values:(NSArray<NSNumber *> *)values {
    // Calculate sum of data
    double sumData = 0;
    for (NSNumber *num in data) {
        sumData += [num doubleValue];
    }
    NSLog(@"Data Sum: %.2f", sumData);

    // Calculate average of values
    double sumValues = 0;
    for (NSNumber *num in values) {
        sumValues += [num doubleValue];
    }
    double avgValues = sumValues / [values count];
    NSLog(@"Values Average: %.2f", avgValues);

    // Check for anomalies (simplified example)
    if (sumData > 100 && avgValues < 10) {
        NSLog(@"Anomaly Detected.");
    } else {
        NSLog(@"No anomaly detected.");
    }

    // Log final report generation time
    NSDate *now = [NSDate date];
    NSLog(@"Report generated at: %@", now);
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        ReportGenerator *generator = [[ReportGenerator alloc] init];
        NSArray<NSNumber *> *sampleData = @[@20.0, @30.0, @60.0];
        NSArray<NSNumber *> *sampleValues = @[@5.0, @8.0, @7.0];
        [generator generateDetailedReportForData:sampleData values:sampleValues];
    }
    return 0;
}

Refactor: Explaining Variable

#import <Foundation/Foundation.h>

@interface PriceCalculator : NSObject
- (CGFloat)calculatePriceForQuantity:(NSInteger)quantity isPremiumCustomer:(BOOL)isPremium hasCoupon:(BOOL)hasCoupon;
@end

@implementation PriceCalculator
- (CGFloat)calculatePriceForQuantity:(NSInteger)quantity isPremiumCustomer:(BOOL)isPremium hasCoupon:(BOOL)hasCoupon {
    CGFloat basePrice = 100.0 * quantity;
    
    // Complex condition
    if (quantity > 10 && isPremium && !hasCoupon) {
        basePrice *= 0.8; // 20% discount
    } else if (quantity > 5 && (isPremium || hasCoupon)) {
        basePrice *= 0.9; // 10% discount
    }
    return basePrice;
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        PriceCalculator *calculator = [[PriceCalculator alloc] init];
        NSLog(@"Price 1: %.2f", [calculator calculatePriceForQuantity:15 isPremiumCustomer:YES hasCoupon:NO]);
        NSLog(@"Price 2: %.2f", [calculator calculatePriceForQuantity:7 isPremiumCustomer:NO hasCoupon:YES]);
    }
    return 0;
}

Refactor: Symbolic Constants

#import <Foundation/Foundation.h>

@interface ScoreEvaluator : NSObject
- (NSString *)evaluateScore:(NSInteger)score;
@end

@implementation ScoreEvaluator
- (NSString *)evaluateScore:(NSInteger)score {
    // Magic numbers: 90, 75, 60
    if (score >= 90) {
        return @"Excellent";
    } else if (score >= 75) {
        return @"Good";
    } else if (score >= 60) {
        return @"Pass";
    } else {
        return @"Fail";
    }
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        ScoreEvaluator *evaluator = [[ScoreEvaluator alloc] init];
        NSLog(@"Score 95: %@", [evaluator evaluateScore:95]);
        NSLog(@"Score 70: %@", [evaluator evaluateScore:70]);
    }
    return 0;
}

Refactor: Consolidate Conditionals

#import <Foundation/Foundation.h>

@interface UserValidator : NSObject
- (BOOL)isUserEligibleForFeature:(BOOL)hasSubscription isActive:(BOOL)isActive isBetaTester:(BOOL)isBetaTester;
@end

@implementation UserValidator
- (BOOL)isUserEligibleForFeature:(BOOL)hasSubscription isActive:(BOOL)isActive isBetaTester:(BOOL)isBetaTester {
    // Original logic:
    if (hasSubscription) {
        return YES;
    }
    if (isActive && isBetaTester) {
        return YES;
    }
    return NO;
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        UserValidator *validator = [[UserValidator alloc] init];
        NSLog(@"User 1 Eligible: %@", [validator isUserEligibleForFeature:YES isActive:NO isBetaTester:NO] ? @"YES" : @"NO");
        NSLog(@"User 2 Eligible: %@", [validator isUserEligibleForFeature:NO isActive:YES isBetaTester:YES] ? @"YES" : @"NO");
        NSLog(@"User 3 Eligible: %@", [validator isUserEligibleForFeature:NO isActive:YES isBetaTester:NO] ? @"YES" : @"NO");
    }
    return 0;
}

Refactor: Move Method/Field

Refactor: Extract Class

#import <Foundation/Foundation.h>

// Before (simplified God Object concept)
@interface UserProfileManager : NSObject
@property (nonatomic, strong) NSString *username;
@property (nonatomic, strong) NSString *email;

- (void)loadUserDataFromRemoteServer;
- (void)saveUserDataToLocalCache;
- (void)displayProfileOnScreen;
- (BOOL)authenticateUserWithPassword:(NSString *)password;
@end

@implementation UserProfileManager
- (void)loadUserDataFromRemoteServer { NSLog(@"Loading user data..."); }
- (void)saveUserDataToLocalCache { NSLog(@"Saving user data..."); }
- (void)displayProfileOnScreen { NSLog(@"Displaying profile..."); }
- (BOOL)authenticateUserWithPassword:(NSString *)password {
    NSLog(@"Authenticating user...");
    return YES;
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        UserProfileManager *manager = [[UserProfileManager alloc] init];
        manager.username = @"coddykit";
        [manager authenticateUserWithPassword:@"password"];
        [manager loadUserDataFromRemoteServer];
        [manager displayProfileOnScreen];
    }
    return 0;
}

Readability: Naming & Style

Refactoring Challenge

Lesson Recap