gistfile1.m

#import <Foundation/Foundation.h>

@interface Account : NSObject
{
    float openingBalance;
    NSString* name;
    NSString* note;
    NSMutableArray* transactions;
}

@property (nonatomic, assign) float openingBalance;
@property (nonatomic, retain) NSString* name;
@property (nonatomic, retain) NSString* note;
@property (nonatomic, retain) NSMutableArray* transactions;

@end

@implementation Account

@synthesize openingBalance;
@synthesize name;
@synthesize note;
@synthesize transactions;

- (id) init
{
    self = [super init];
    if (self != nil) {
        openingBalance = 123.456f;
        name = [[NSString alloc] initWithString:@"NAME"];
        note = [[NSString alloc] initWithString:@"NOTE"];
        transactions = [[NSMutableArray alloc] init];
    }
    return self;
}

- (void)dealloc {
    [name release];
    [note release];
    [transactions release];
    [super dealloc];
}

@end

@interface Transaction : NSObject
{
    unsigned int referenceNumber;
    double amount;
    NSString* payee;
    NSDate* date;
    NSString* category;
    BOOL reconciled;
}

@property (nonatomic, assign) unsigned int referenceNumber;
@property (nonatomic, assign) double amount;
@property (nonatomic, retain) NSString* payee;
@property (nonatomic, retain) NSDate* date;
@property (nonatomic, retain) NSString* category;
@property (nonatomic, assign) BOOL reconciled;

@end

@implementation Transaction

@synthesize referenceNumber;
@synthesize amount;
@synthesize payee;
@synthesize date;
@synthesize category;
@synthesize reconciled;

- (id) init
{
    self = [super init];
    if (self != nil) {
        referenceNumber = 123;
        amount = 123.456;
        payee = [[NSString alloc] initWithString:@"PAYEE"];
        date = [[NSDate alloc] init];
        category = [[NSString alloc] initWithString:@"CATEGORY"];
        reconciled = NO;
    }
    return self;
}

- (void)dealloc {
    [payee release];
    [date release];
    [category release];
    [super dealloc];
}

@end

int main() {
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];

    NSMutableArray* accountArray = [NSMutableArray array];

    Account* account1 = [[Account alloc] init];
    account1.openingBalance = 1000.0f;
    [accountArray addObject:account1];
    [account1 release];
    NSLog(@"%@", [accountArray valueForKeyPath:@"@avg.openingBalance"]);

    Account* account2 = [[Account alloc] init];
    account2.openingBalance = 2000.0f;
    [accountArray addObject:account2];
    [account2 release];
    NSLog(@"%@", [accountArray valueForKeyPath:@"@avg.openingBalance"]);

    Account* account3 = [[Account alloc] init];
    account3.openingBalance = 3000.0f;
    [accountArray addObject:account3];
    [account3 release];
    NSLog(@"%@", [accountArray valueForKeyPath:@"@avg.openingBalance"]);

    Account* savingsAccount = [[Account alloc] init];

    Transaction* transaction1 = [[Transaction alloc] init];
    [savingsAccount.transactions addObject:transaction1];
    [transaction1 release];

    Transaction* transaction2 = [[Transaction alloc] init];
    [savingsAccount.transactions addObject:transaction2];
    [transaction2 release];

    Transaction* transaction3 = [[Transaction alloc] init];
    [savingsAccount.transactions addObject:transaction3];
    [transaction3 release];

    NSLog(@"%@", [savingsAccount valueForKeyPath:@"transactions.@count"]);

    [pool release];

    return 0;
}