objective_c — consolidated language guide — DedSec Project

Objective-C

Typical use: General-purpose programming.

Suggested file extension: .m.

How to run / environment: Compile with clang and a compatible Foundation runtime.

Starter example

#import <Foundation/Foundation.h>
int main(void) {
  @autoreleasepool { NSLog(@"Hello, Ada!"); }
  return 0;
}

How to read it

Foundation availability differs by operating system.

Common pitfall

Foundation availability differs by operating system.

Objective_C — Focused mastery pathway

Target environment

Objective-C language support does not imply the Apple Foundation framework is present. Choose either macOS with Foundation and ARC or GNUstep with an explicitly verified build command. The example below targets macOS Foundation and clang -fobjc-arc -framework Foundation Inventory.m -o inventory. Do not report it as tested on Linux without GNUstep adaptation.

Minimal ownership and validation fixture

#import <Foundation/Foundation.h>

@interface Inventory : NSObject
@property (nonatomic, strong) NSMutableDictionary<NSString *, NSNumber *> *stock;
- (BOOL)addSKU:(NSString *)sku quantity:(NSInteger)quantity;
- (BOOL)sellSKU:(NSString *)sku quantity:(NSInteger)quantity;
@end

@implementation Inventory
- (instancetype)init {
    if ((self = [super init])) _stock = [NSMutableDictionary dictionary];
    return self;
}
- (BOOL)addSKU:(NSString *)sku quantity:(NSInteger)quantity {
    if (!sku || sku.length == 0 || quantity < 0 || self.stock[sku]) return NO;
    self.stock[sku] = @(quantity);
    return YES;
}
- (BOOL)sellSKU:(NSString *)sku quantity:(NSInteger)quantity {
    NSNumber *old = self.stock[sku];
    if (!old || quantity <= 0 || quantity > old.integerValue) return NO;
    self.stock[sku] = @(old.integerValue - quantity);
    return YES;
}
@end

int main(void) {
    @autoreleasepool {
        Inventory *items = [Inventory new];
        NSCAssert([items addSKU:@"A-1" quantity:5], @"first insert");
        NSCAssert(![items addSKU:@"A-1" quantity:7], @"duplicate rejected");
        NSCAssert([items sellSKU:@"A-1" quantity:2], @"sale");
        NSCAssert([items.stock[@"A-1"] integerValue] == 3, @"remaining");
        NSLog(@"PASS");
    }
    return 0;
}

Model interpretation

Under ARC, strong retains the dictionary and @autoreleasepool bounds autoreleased objects; avoid manually calling release in ARC code. Dictionary subscripting returns nil for absent keys, but nil and the NSNumber value zero are not equivalent. The current API returns NO on bad inputs; a production API might prefer NSError ** with distinct error codes and user-facing messages.

Adversarial lab

Try empty SKU, duplicate SKU, sale exceeding stock, zero sale, and missing key. For each, verify that the stored quantity did not change. Add a dispatch_queue_t concurrency exercise: demonstrate that unsynchronized mutable dictionaries must not be treated as thread-safe and design serialized writes or a lock. Avoid benchmarking unsynchronized races as reliable output.

Platform, testing and documentation

On macOS record clang --version, target architecture and Foundation SDK version. On GNUstep record exact gnustep-config flags and ARC/runtime compatibility; adapt tests to that runtime. Build twice from a clean folder, enable warnings, and preserve compiler output. Document the limits of NSCAssert in optimized builds and supplement it with explicit programmatic tests.