Text label is blank when you press the button

PViewController.h
//
//  PMViewController.h
//  CrystalBall
//
//  Created by Ben Junya on 7/16/14.
//  Copyright (c) 2014 Prism-Mobile. All rights reserved.
//

#import <UIKit/UIKit.h>

@class PMCrystalBall;

@interface PMViewController : UIViewController
@property (strong, nonatomic) IBOutlet UILabel *predictionLabel;

@property (strong, nonatomic) PMCrystalBall *crystalBall;
- (IBAction)buttonPressed;

@end

PMViewController.m
//
//  PMViewController.m
//  CrystalBall
//
//  Created by Ben Junya on 7/16/14.
//  Copyright (c) 2014 Prism-Mobile. All rights reserved.
//

#import "PMViewController.h"
#import "PMCrystalBall.h"
@interface PMViewController ()

@end

@implementation PMViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.crystalBall = [[PMCrystalBall alloc] init];
}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)buttonPressed {


    self.predictionLabel.text = [self.crystalBall randomPrediction];

}
@end

PMCrystalBall.h
//
//  PMCrystalBall.h
//  CrystalBall
//
//  Created by Ben Junya on 7/18/14.
//  Copyright (c) 2014 Prism-Mobile. All rights reserved.
//

#import <Foundation/Foundation.h>



@interface PMCrystalBall : NSObject {
    NSArray *_predictions;

}



@property (strong, nonatomic, readonly) NSArray *predictions;
@property (strong, nonatomic) NSString *randomPrediction;

-(NSString*) randomPrediciton;

@end

PMCrystalBall.m

//
//  PMCrystalBall.m
//  CrystalBall
//
//  Created by Ben Junya on 7/18/14.
//  Copyright (c) 2014 Prism-Mobile. All rights reserved.
//

#import "PMCrystalBall.h"

@implementation PMCrystalBall

-(NSArray*) predictions {
    if (_predictions == nil) {
        _predictions = [[NSArray alloc] initWithObjects:

                        @"It is certain",
                        @"It is decidedly so",
                        @"All signs say yes",
                        @"The stars are not aligned",
                        @"My reply is no",
                        @"It is doubtful",
                        @"Better not tell you now",
                        @"Concentrate and ask again",
                        @"Unable to answer now", nil];
    }
    return _predictions;
}
-(NSString*) randomPrediciton {
    int random = arc4random_uniform(self.predictions.count);
    return [self.predictions objectAtIndex:random];
}

@end