Challenge 21.02 from Russia

Objective-C Programming (2nd Edition) 21. Object Instance Variables and Properties
1 
**BNRPerson.h**

#import <Foundation/Foundation.h>

@interface BNRPerson : NSObject

// BNRPerson has two properties
@property (nonatomic) float heightInMeters;
@property (nonatomic) int weightInKilos;
@property (nonatomic, readonly) double circumferenceOfEarth;
@property (nonatomic, readwrite) double humanPopulation;

// BNRPerson has a method that calculates the Body Mass Index
- (float)bodyMassIndex;

@end

**BNRPerson.m**

#import "BNRPerson.h"

@implementation BNRPerson

- (float)bodyMassIndex
{
    float h = [self heightInMeters];
    return [self weightInKilos] / (h * h);
}

@end

**BNREmployee.h**

#import "BNRPerson.h"
@class BNRAsset;

@interface BNREmployee : BNRPerson
{
    NSMutableArray *_assets;
}

@property (nonatomic) unsigned int employeeID;
@property (nonatomic) unsigned int officeAlarmCode;
@property (nonatomic) NSDate *hireDate;
@property (nonatomic, copy) NSArray *assets;

- (double)yearsOfEmployment;
- (void)addAsset:(BNRAsset *)a;
- (void)removeAsset:(BNREmployee *)a;
- (unsigned int)valueOfAssets;

@end

**BNREmployee.m**

#import "BNREmployee.h"
#import "BNRAsset.h"

@implementation BNREmployee

// Accessors for assets properties
- (void)setAssets:(NSArray *)a
{
    _assets = [a mutableCopy];
}

- (NSArray *)assets
{
    return [_assets copy];
}

- (void)addAsset:(BNRAsset *)a
{
    // Is assets nil?
    if (!_assets) {
        
        // Create the array
        _assets = [[NSMutableArray alloc] init];
    }
    [_assets addObject:a];
}

- (void)removeAsset:(BNREmployee *)a
{
    // Test if _assets is nil or zero
    
    if (_assets == nil || _assets == 0)
    {
        NSLog(@"Employee ID:%u has no assets", self.employeeID);
        return;
    }
    
    // When assets count reaches zero, then exit the loop
    // i is not incremented in this loop
    
    for (int i = 0; i < [_assets count];)
    {
        [_assets removeObjectAtIndex:i];
    }
}

- (unsigned int)valueOfAssets
{
    // Sum up the resale value of the assets
    unsigned int sum = 0;
    for (BNRAsset *a in _assets) {
        sum += [a resaleValue];
    }
    return sum;
}

- (double)yearsOfEmployment
{
    // Do i have non-nil hireDate?
    if (self.hireDate) {
        // NSTimeInterval is the same as double
        NSDate *now = [NSDate date];
        NSTimeInterval secs = [now timeIntervalSinceDate:self.hireDate];
        return secs / 31557600.0;   // Seconds per year
    } else {
        return 0;
    }
}

- (float)bodyMassIndex
{
//    return 19.0;
    float normalBMI = [super bodyMassIndex];
    return normalBMI * 0.9;
}

- (NSString *)description
{
    return [NSString stringWithFormat:@"<Employee %u: $%u in assets",
            self.employeeID, self.valueOfAssets];
}

- (void)dealloc
{
    NSLog(@"deallocating %@", self);
}

@end

**BNRAsset.h**

#import <Foundation/Foundation.h>

@interface BNRAsset : NSObject

@property (nonatomic, copy) NSString *label;
@property (nonatomic) unsigned int resaleValue;

@end

**BNRAsset.m**

#import "BNRAsset.h"

@implementation BNRAsset

- (NSString *)description;
{
    return [NSString stringWithFormat:@"<%@: $%u>", self.label, self.resaleValue];
}

- (void)dealloc
{
    NSLog(@"deallocating %@", self);
}

@end

**main.m**

#import <Foundation/Foundation.h>
#import "BNREmployee.h"
#import "BNRAsset.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        // Create an instance of BNREmployee objects
        NSMutableArray *employees = [[NSMutableArray alloc] init];
        
        for (int i = 0; i < 10; i++) {
            // Create an instance of BNREmployee
            BNREmployee *mikey = [[BNREmployee alloc] init];
            
            // Give the instance variables interesting values
            mikey.weightInKilos = 90 + i;
            mikey.heightInMeters = 1.8 - i/10.0;
            mikey.employeeID = i;
            
            // Put the employee in the employees array
            [employees addObject:mikey];
        }
        
        // Create 10 assets
        for (int i = 0; i < 10; i++) {
            // Create an asset
            BNRAsset *asset = [[BNRAsset alloc] init];
            
            // Give it an interesting label
            NSString *currentLabel = [NSString stringWithFormat:@"Laptop %d", i];
            asset.label = currentLabel;
            asset.resaleValue = 350 + i * 17;
            
            // Get a random number between 0 and 9 inclusive
            NSUInteger randomIndex = random() % [employees count];
            
            // Find that employee
            BNREmployee *randomEmployee = [employees objectAtIndex:randomIndex];
            
            // Assign the asset to the employee
            [randomEmployee addAsset:asset];
        }
        
        for (int i = 0; i < 10; i++)
        {
            // Get a random number
            NSUInteger randomIndex = random() % [employees count];
            
            // Random employee chosen from employees array
            BNREmployee *randomEmployee = [employees objectAtIndex:randomIndex];
            
            // Remove all assets from randomEmployee
            NSLog(@"Employees: %@", randomEmployee);
            NSLog(@"Giving up ownership of %@ employee\n", randomEmployee);
            [randomEmployee removeAsset:randomEmployee];
        }
        
        NSLog(@"Giving up ownership of arrays");
        employees = nil;
    }
    return 0;
}
2

This looks cool. There is no one to solve this riddle?