Why is shouldStartLoadWithRequest only being invoked the first time through?

Question

I'm trying to display a list of web pages the user can switch between in my app. I've done this successfully with documents. however, I don't want the user to be able to navigate from these pages. I found out how to do this by looking it up. The problem is that it only executes on the first page. When I switch to another page shouldStartLoadWithRequest stops working even when I go back to the first page. (This is all done with my specially designed back and forward buttons.) How can I fix this so that it will be invoked every single time and prevent the user from clicking links and navigating away from my set pages? I'm new to objective-c. All the relevant code is below. Some things were declared globally in the .h. Sorry it's kind of rough. I tabbed over only what was needed to make it into code formatting. Thanks!

My .h file:

#import <UIKit/UIKit.h>

@interface learnViewController : UIViewController <UINavigationControllerDelegate>
{
    IBOutlet UIWebView *web;
    UIButton *backButton;
    UIButton *forButton;
}
@end

My .m file

#import "learnViewController.h"
#import "ViewController.h"

static NSString* links[] =
{
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000141.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000065.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/001087.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000091.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/007270.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000145.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000093.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000087.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000140.htm",
    @"http://www.nlm.nih.gov/medlineplus/ency/article/000132.htm"
};
int numlinks = 10;
int i = 0;

@interface learnViewController ()

@end

@implementation learnViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    float viewWidth = self.view.frame.size.width;
    float viewHeight = self.view.frame.size.height;

    self.view.multipleTouchEnabled = true;
    //Background
    UIImageView *backgroundView = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, viewWidth, viewHeight)];
    backgroundView.image = [UIImage imageNamed:@"Background.png"];
    [self.view addSubview:backgroundView];
    //Show Portal
    web = [[UIWebView alloc]initWithFrame:CGRectMake(0.0, viewHeight/34.0, viewWidth, (viewHeight - viewHeight/6.4))];
    self->web.delegate = self;
    web.scrollView.scrollEnabled = TRUE;
    web.scalesPageToFit = TRUE;
    [self loadDocument:links[i] inView:web];
    [self.view addSubview:web];
    //Buttons
    UIButton *homeButton = [[UIButton alloc] initWithFrame:CGRectMake((viewWidth/2.0 - viewWidth/6.0/2.0), (viewHeight - viewHeight*280.0/2208.0/2.0 - viewWidth/6.0/2.0), (viewWidth/6.0), (viewWidth/6.0))];
    [homeButton
     setBackgroundImage:[UIImage imageNamed:@"Home.png"]
     forState:UIControlStateNormal];
    [homeButton addTarget:self action:@selector(homePressed:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:homeButton];

    backButton = [[UIButton alloc] initWithFrame:CGRectMake((viewWidth/2.0/3.5 - viewWidth/9.0/2.0), (viewHeight - viewHeight*280.0/2208.0/2.0 - viewWidth/9.0/2.0), (viewWidth/9.0), (viewWidth/9.0))];
    [backButton
     setBackgroundImage:[UIImage imageNamed:@"Back.png"]
     forState:UIControlStateNormal];
    backButton.enabled = FALSE;
    [backButton addTarget:self
                   action:@selector(backPressed:)
         forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:backButton];

    forButton = [[UIButton alloc] initWithFrame:CGRectMake((viewWidth/2.0/3.5*2.0 - viewWidth/9.0/2.0), (viewHeight - viewHeight*280.0/2208.0/2.0 - viewWidth/9.0/2.0), (viewWidth/9.0), (viewWidth/9.0))];
    [forButton
     setBackgroundImage:[UIImage imageNamed:@"Forward.png"]
     forState:UIControlStateNormal];
    [forButton addTarget:self
                  action:@selector(forPressed:)
        forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:forButton];

    UIButton *refButton = [[UIButton alloc] initWithFrame:CGRectMake((viewWidth - viewWidth/2.0/3.5*2.0 - viewWidth/9.0/2.0), (viewHeight - viewHeight*280.0/2208.0/2.0 - viewWidth/9.0/2.0), (viewWidth/9.0), (viewWidth/9.0))];
    [refButton
     setBackgroundImage:[UIImage imageNamed:@"Scale.png"]
     forState:UIControlStateNormal];
    [refButton addTarget:self
                  action:@selector(refPressed:)
        forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:refButton];

    UIButton *webButton = [[UIButton alloc] initWithFrame:CGRectMake((viewWidth - viewWidth/2.0/3.5 - viewWidth/9.0/2.0), (viewHeight - viewHeight*280.0/2208.0/2.0 -     viewWidth/9.0/2.0), (viewWidth/9.0), (viewWidth/9.0))];
    [webButton
     setBackgroundImage:[UIImage imageNamed:@"Web.png"]
     forState:UIControlStateNormal];
    [webButton addTarget:self
                  action:@selector(webPressed:)
        forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:webButton];
}
//Button presses
-(void)homePressed:(id)sender
{
    ViewController *home = [[ViewController alloc] initWithNibName:nil bundle:nil];
    [self presentViewController:home animated:YES completion:NULL];
}

- (void) refPressed:(id)sender
{
    [self loadDocument:links[i] inView:web];
}

-(void)backPressed:(id)sender
{
    float viewWidth = self.view.frame.size.width;
    float viewHeight = self.view.frame.size.height;
    if (i > 0)
    {
        [web removeFromSuperview];
        i--;
        web = [[UIWebView alloc] initWithFrame:CGRectMake(0.0, viewHeight/34.0, viewWidth, (viewHeight - viewHeight/6.4))];
        [self loadDocument:links[i] inView:web];
        web.scrollView.scrollEnabled = TRUE;
        web.scalesPageToFit = TRUE;
        [self.view addSubview:web];
        forButton.enabled = TRUE;
    }
    if (i == 0)
    {
        backButton.enabled = FALSE;
    }
}

-(void)forPressed:(id)sender
{
    float viewWidth = self.view.frame.size.width;
    float viewHeight = self.view.frame.size.height;
    if (i < numlinks - 1)
    {
        [web removeFromSuperview];
        i++;
        web = [[UIWebView alloc] initWithFrame:CGRectMake(0.0, viewHeight/34.0, viewWidth, (viewHeight - viewHeight/6.4))];
        [self loadDocument:links[i] inView:web];
        web.scrollView.scrollEnabled = TRUE;
        web.scalesPageToFit = TRUE;
        [self.view addSubview:web];
        backButton.enabled = TRUE;
    }
    if (i == numlinks - 1)
    {
        forButton.enabled = FALSE;

    }
}

-(void)loadDocument:(NSString*)documentName inView:(UIWebView*)webView
{
    NSString *url = links[i];
    NSURL *nsurl = [NSURL URLWithString:url];
    NSURLRequest *nsrequest = [NSURLRequest requestWithURL:nsurl];
    [webView loadRequest:nsrequest];
}

-(void)webPressed:(id)sender
{
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:links[i]]];
}

-(BOOL) webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    NSURL *url = request.URL;
    NSString *urlString = url.absoluteString;
    NSRange range = [urlString rangeOfString:links[i]];
    if (range.location != NSNotFound)
    {
        return YES;
    }
    else
    {
        return NO;
    }
}

- (void)viewDidUnload
{
    [self->web stopLoading];
    self->web.delegate = nil;
}

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

@end

Answer 1

Okay, I figured it out through trial and error since no one wanted to help me. I tried looking for answers to similar questions, but nothing actually worked for me. If you're reading this and having the same problem, this is how you fix it. All you have to do is reset the web delegate to nil then back to self as so:

self.webView.delegate = nil;
self.webView.delegate = self;

I don't know why everyone else's code was so complex, and I can only speculate as to why this works. I just got lucky honestly, but I think it maybe clears the cache when you do this, thus making each page fresh to the program. That's what other people were talking about. However, their methods did not work for me either because of my lack of experience or because they do not fit my particular case. This is much simpler and is guaranteed to work as long as you make sure it does this each time you load one of your designated web pages. You're welcome if you're reading this. If anyone would so kindly as to look at my post and explain why this works in better detail, please feel free to do so!