Help a noob with inheritance

[Ben Alex Barreto]

So I've been trying to learn Objective-C, and yesterday I was looking at how inheritance works.

I created two classes, Person and Employee. The later is supposed to inherit from Person. The problem is that I'm getting this error "No visible @inerface for Employee" when I try to instantiate an Employee and set its weightInKilos or heightInMeters. Here are the header and implementation files:

//
//  Employee.h
//  BMITime
//
//  Created by Benjamin Barreto on 5/1/12.
//  Copyright (c) 2012 BYU-Idaho. All rights reserved.
//

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

@interface Employee : Person {
    int employeeID;
}

@property int employeeID;

- (float)bodyMassIndex;

@end

//
//  Employee.m
//  BMITime
//
//  Created by Benjamin Barreto on 5/1/12.
//  Copyright (c) 2012 BYU-Idaho. All rights reserved.
//

#import "Employee.h"

@implementation Employee

@synthesize employeeID;

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

@end

//
//  Person.h
//  BMITime
//
//  Created by Benjamin Barreto on 4/30/12.
//  Copyright (c) 2012 BYU-Idaho. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Person : NSObject {
    // It has two instance variables
    float heightInMeters;
    int weightInKilos;
}

@property float heightInMeters;
@property int weightInKilos;

// This method calculates the Body Mass Index
- (float)bodyMassIndex;

@end

//
//  Person.m
//  BMITime
//
//  Created by Benjamin Barreto on 4/30/12.
//  Copyright (c) 2012 BYU-Idaho. All rights reserved.
//

#import "Person.h"

@implementation Person

@synthesize heightInMeters, weightInKilos;

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

@end

And here is the main

//
//  main.m
//  BMITime
//
//  Created by Benjamin Barreto on 4/29/12.
//  Copyright (c) 2012 BYU-Idaho. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Person.h"
#import "Employee.h"

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

    @autoreleasepool {
        
        // Create an instance of Person
        Person *person = [[Person alloc] init];
        Employee *em = [[Employee alloc] init];
        
        // Give the instance variables interesting values
        [person setWeightInKilos:96];
        [person setHeightInMeters:1.8];
        
        [em setWeightInKilos:99];
        [em setHeightInMeters:2.2];
        [em setEmployeeID:15];
        
        // Call the bodyMassIndex method
        float bmi = [person bodyMassIndex];
        NSLog(@"person (%d, %f) has a BMI of %f", [person weightInKilos], [person heightInMeters], bmi);
        
    }
    return 0;
}

I'm just trying to learn. What am I doing wrong?

[Hussein Baghdadi]

I copied your code and run it with a flying colors without any error.

Do you a duplicated file here and there (such as Person.h/Person.m/Employee.h/Employee.m) ?