Placing a UIToolbar above a keyboard in Xcode 4.3

This is my first post and I'm brand new to iOS programming. I am using xcode 4.3 and have probably a simple question. I examined all the ways to place the toolbar above the keyboard, on which there is a previous / next button. I found a few questions on how to do this when xcode uses an interface builder. But I can not find one that is designed for the latest version of xcode. So I took what I found on the Internet and from the Apple dev site, and came up with some kind of code. The only thing is not working! I get an error message that says about the purpose of the readonly property in the lines with inputAcessoryView. I know that this is probably something simple, but when transferring the code from the previous version to the newer version, I most likely messed up something. Can someone check my code and tell me what I did wrong.Thank. I included .h / .m files

    #import <UIKit/UIKit.h>

    @interface keyboardViewController : UIViewController


    @property (retain, nonatomic) IBOutlet UIView *textField1;
    @property (retain, nonatomic) IBOutlet UIView *textField2;

    @property (nonatomic, retain) UIToolbar *keyboardToolbar;

    -(void)resignKeyboard:(id)sender;
    -(void)previousField:(id)sender;
    -(void)nextField:(id)sender;

    @end

implimentation

    #import "keyboardViewController.h"

    @interface keyboardViewController ()

    @end

    @implementation keyboardViewController
    @synthesize textField1;
    @synthesize textField2;
    @synthesize keyboardToolbar;

    - (void)viewDidLoad
    {
        [super viewDidLoad];

        if (keyboardToolbar == nil)
        {
            keyboardToolbar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0,                            self.view.bounds.size.width, 44)]; 

            UIBarButtonItem *previousButton = [[UIBarButtonItem alloc] initWithTitle:@"previous" 
                                                                               style:UIBarButtonItemStyleBordered
                                                                      target:self 
                                                                      action:@selector(previousField:)];
            UIBarButtonItem *nextButton = [[UIBarButtonItem alloc] initWithTitle:@"next" 
                                                                           style:UIBarButtonItemStyleBordered
                                                                          target:self 
                                                                          action:@selector(nextField:)];

            UIBarButtonItem *extraSpace = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:(UIBarButtonSystemItemFlexibleSpace) target:nil action:nil];


            UIBarButtonItem *done = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:(UIBarButtonSystemItemDone) target:self action:@selector(resignKeyboard:)];



            [keyboardToolbar setItems:[[NSArray alloc] initWithObjects:previousButton, nextButton, extraSpace, done, nil]];

            textField1.inputAccessoryView  = keyboardToolbar;
            textField2.inputAccessoryView  = keyboardToolbar;


        }


    }

    -(void) resignKeyboard:(id)sender
    {
        if ([textField1 isFirstResponder])
            [textField1 resignFirstResponder];

        else if ([textField2 isFirstResponder])
        [textField2 resignFirstResponder];
    }

    -(void) previousField:(id)sender
    {
        if ([textField1 isFirstResponder])
            [textField2 becomeFirstResponder];

        else if ([textField2 isFirstResponder])
            [textField1 becomeFirstResponder];
    }


    -(void) nextField:(id)sender
    {
        if ([textField1 isFirstResponder])
            [textField2 becomeFirstResponder];

        else if ([textField2 isFirstResponder])
            [textField1 becomeFirstResponder];
    }


    - (void)viewDidUnload
    {
        [self setTextField1:nil];
        [self setTextField2:nil];
        [self setKeyboardToolbar:nil];
        [super viewDidUnload];
        // Release any retained subviews of the main view.
    }

    - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
    {
        return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
    }

    @end