Protocols, delegates, and Categories

CreatureProtocol.h

//
//  CreatureProtocol.h
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

@protocol CreatureProtocol <NSObject>

@required
-(void) sayHello;

@end

Dog+Pooping.h

//
//  Dog+Pooping.h
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Dog.h"

@interface Dog(Pooping)

-(void) po_doBusiness;

@end

Dog+Pooping.m

//
//  Dog+Pooping.m
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import "Dog+Pooping.h"
#import "Dog.h"

@implementation Dog(Pooping)

-(void) po_doBusiness{
    NSLog(@"I'm going to make eye contact with you while I poop");
}

@end

Dog.h

//
//  Dog.h
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "CreatureProtocol.h"

@protocol DogOwnerProtocol <NSObject>

-(void) takeDogForWalk;

@end

@interface Dog : NSObject<CreatureProtocol>

@property (nonatomic, strong) NSString *nickname;

@property (nonatomic, assign) id<DogOwnerProtocol> delegate;


-(void) needsToWalk;

@end

Dog.m

//
//  Dog.m
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import "Dog.h"

@implementation Dog

-(void) sayHello{
    
    NSLog(@"Woof, bow wow.");
    
}

-(void) needsToWalk{
    [self.delegate takeDogForWalk];
}

@end

Instructor.h

//
//  Instructor.h
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Dog.h"

@interface Instructor : NSObject<DogOwnerProtocol>

@end

Instructor.m

//
//  Instructor.m
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import "Instructor.h"

@implementation Instructor

-(void)takeDogForWalk{
    NSLog(@"Instuctor takes dog for walk");
}


@end

main.m

//
//  main.m
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import <Foundation/Foundation.h>

#import "Student.h"
#import "Instructor.h"

#import "Dog.h"
#import "Dog+Pooping.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSLog(@"The program has started");
        
        NSNull *a = [[NSNull alloc] init]; //Isn' this the most insane thing ever?
        
        NSDictionary *testDictionary = @{@"one": @1, @"two": @2, @"three":@3};
        
        NSDictionary *subDictionary = [testDictionary valuesForKeys:@[@"one", @"four"]];
        
        if (![testDictionary objectForKey:@"five"]){
            NSLog(@"this is testing nil and will work");
        }
        
        if (![subDictionary objectForKey:@"four"]){
            NSLog(@"this is testing NSNUll and will not fire");
        }
        
        if ([[subDictionary objectForKey:@"four"] isKindOfClass:[NSNull class]]){
            NSLog(@"this is testing for NSNUll");
        }
        
        Student *student1 = [[Student alloc] init];
        student1.firstName = @"Arsalan";
        
        if (!student1.nickname){
            NSLog(@"Student 1 has no nickname");
        }
        
        if (student1.nickname){
            NSLog(@"Student 1 has nickname");
        }
        
        Dog *dog1 = [[Dog alloc] init];
        dog1.nickname = @"Ella";
        
        NSArray *officeCreatures = @[student1, dog1];
        
        for ( id<CreatureProtocol> creature in officeCreatures){
            [creature sayHello];
        }
        
        //Protocol/delegate examples
        
        Instructor *instructor = [[Instructor alloc] init];
        
        dog1.delegate = instructor;
        
        [dog1 needsToWalk];
        
        
        //From here, let's assume, for some bizarre reason, we can't extend Dog
        
        [dog1 po_doBusiness];
        
    }
    return 0;
}

Student.h

//
//  Student.h
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "CreatureProtocol.h"
#import "Dog.h"

@interface Student : NSObject<CreatureProtocol, DogOwnerProtocol>

@property (nonatomic, strong) NSString *firstName;
@property (nonatomic, strong) NSString *nickname;

@end

Student.m

//
//  Student.m
//  Classroom
//
//  Created by Ian MacKinnon on 2015-06-12.
//  Copyright (c) 2015 Ian MacKinnon. All rights reserved.
//

#import "Student.h"

@implementation Student

-(void) sayHello{
    
    NSLog(@"Hello, my name is %@", _firstName);
    
}

-(void)takeDogForWalk{
    NSLog(@"Student takes dog for walk");
}

@end