Objective C - tutorial

City.h

//
//  City.h
//  city
//
//  Created by Kirill Klenov on 09.11.13.
//  Copyright (c) 2013 Kirill Klenov. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface City : NSObject {
    
    NSString* name;
    int age;
    int population;
    
}

- (void) setName: (NSString*) n;
- (NSString*) getName;

- (void) setAge: (int) a;
- (int) getAge;

- (void) setPopulation: (int) p;
- (int) getPopulation;

- (void) nextDay;

- (void) print;

@end

City.m

//
//  City.m
//  city
//
//  Created by Kirill Klenov on 09.11.13.
//  Copyright (c) 2013 Kirill Klenov. All rights reserved.
//

#import "City.h"

@implementation City

- (id) init {
    self = [super init];
    if (self) {
        self.population = arc4random() % 100;
    }
    return self;
}

- (void) setName:(NSString *)n {
    name = n;
}

- (NSString*) getName {
    return name;
}

- (void) setAge:(int)a {
    age = a;
}

- (int) getAge {
    return age;
}

- (void) setPopulation:(int)p {
    population = p;
}

- (int) getPopulation {
    return population;
}

- (void) nextDay {
    population += arc4random() % population;
    population -= arc4random() % population;
}

- (void) print {
    NSLog(@"%@ (%i) %i", name, population, age);
}

@end

main.m

//
//  main.m
//  city
//
//  Created by Kirill Klenov on 09.11.13.
//  Copyright (c) 2013 Kirill Klenov. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "City.h"
#import "Metropolis.h"


int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        City *city;
        city = [[City alloc] init];
        [city setName:@"Default City"];
        for (int i = 0; i < 10; i++) {
            [city nextDay];
            [city print];
        };
        
        Metropolis *metropolis = [[Metropolis alloc] init];
        
        [metropolis createCity:@"City1" atIndex:0 withPopulation:100];
        [metropolis createCity:@"City2" atIndex:1 withPopulation:110];
        [metropolis createCity:@"City3" atIndex:2 withPopulation:120];
        [metropolis createCity:@"City4" atIndex:3 withPopulation:130];
        [metropolis createCity:@"City5" atIndex:4 withPopulation:140];
        [metropolis createCity:@"City6" atIndex:5 withPopulation:150];
        [metropolis createCity:@"City7" atIndex:6 withPopulation:160];
        [metropolis createCity:@"City8" atIndex:7 withPopulation:170];
        [metropolis createCity:@"City9" atIndex:8 withPopulation:180];
        [metropolis createCity:@"City0" atIndex:9 withPopulation:190];
        
        for (int i = 0; i < 10; i++) {
            city = [metropolis getCities][i];
            [city nextDay];
            [city print];
        }
        
        
    }
    return 0;
}

Metropolis.h

//
//  Metropolis.h
//  city
//
//  Created by Kirill Klenov on 09.11.13.
//  Copyright (c) 2013 Kirill Klenov. All rights reserved.
//

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

@interface Metropolis : NSObject

- (City*) createCity:(NSString*)n atIndex:(int)i withPopulation:(int)p;

- (NSMutableArray*) getCities;

@end

Metropolis.m

//
//  Metropolis.m
//  city
//
//  Created by Kirill Klenov on 09.11.13.
//  Copyright (c) 2013 Kirill Klenov. All rights reserved.
//

#import "Metropolis.h"
#import "City.h"

@implementation Metropolis {
    
    NSMutableArray *cities;
    
}

- (id)init {
    
    self = [super init];
    cities = [[NSMutableArray alloc] initWithCapacity:10];
    return self;
    
}

- (NSMutableArray*) getCities {
    return cities;
}

- (City*) createCity:(NSString*)n atIndex:(int)i withPopulation:(int)p {
    
    City *city = [[City alloc] init];
    [city setName:n];
    [city setPopulation:p];
    [cities insertObject:city atIndex:i];
    return city;
    
}

@end