user3567992 user3567992 - 2 months ago 19
iOS Question

Modify Request of webView shouldStartLoadWithRequest:

Currently I am developing an hybrid app which uses webView shouldStartLoadWithRequest: to provide a token for the login. My function works fine for every normal request I make (a click e.g.)

- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request
NSLog([NSString stringWithFormat:@"Loading View: %@",[[request URL] absoluteString]]);
if ([[[request URL] absoluteString] rangeOfString:BASE_URL].location != NSNotFound) {
NSString *token = [[NSUserDefaults standardUserDefaults] stringForKey:kDefaultsKeyLoginToken];
NSString *hash = [[NSUserDefaults standardUserDefaults] stringForKey:kDefaultsKeyLoginHash];
NSString *params = [NSString stringWithFormat:@"mobile=app&user_token=%@&user_hash=%@",token,hash];
if([[request URL] query] == nil) {
[self LoadUrl:[[request URL] absoluteString] withGetParams:params append:NO];
return NO;
}else{
if([[[request URL] absoluteString] rangeOfString:params].location == NSNotFound){
[self LoadUrl:[[request URL] absoluteString] withGetParams:params append:YES];
return NO;
}
}

}

-(void)LoadUrl:(NSString *)url withGetParams:(NSString *)params append:(BOOL)append{
NSString *PreUrl;
if(append == YES) PreUrl = [NSString stringWithFormat:@"%@&%@",url,params];
else PreUrl = [NSString stringWithFormat:@"%@?%@",url,params];
NSURL *nsurl = [NSURL URLWithString: PreUrl];
NSURLRequest *request = [NSURLRequest requestWithURL:nsurl];
[self.WebView loadRequest:request];
}


The Problem I have with this Code is that if I load an Image e.g. it will be detected as "to be hashed-appended" (which is correct, I want every request to have the Auth included) BUT the Image will get loaded in the Webview itself.

My first try (before I switched to this model) was to modify the request parsed. But every change got Ignored....

Has anyone an Idea how I could fix this problem? Is there a way to really modify requests? Or if not, can I at least determine the "target" of the request or forward it?

Thanks for any help

Answer

I found a Solution for my Problem. Sublcassing was the right approach but not UIWebView but a own NSURLProtocol.

So what I did:

Create an own Sublcass of NSURLProtocol

@interface MyURL : NSURLProtocol <NSURLConnectionDelegate>

Add some standard handling for HTTP-Connections

@interface MyURL () <NSURLConnectionDelegate>

@property (nonatomic, strong) NSURLConnection *connection;
@property (nonatomic, strong) NSMutableData *mutableData;
@property (nonatomic, strong) NSURLResponse *response;

@end

@implementation MyURL
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request
{
    return request;
}
- (void)stopLoading
{
    [self.connection cancel];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.client URLProtocol:self didLoadData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [self.client URLProtocol:self didFailWithError:error];
    self.connection = nil;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageAllowed];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [self.client URLProtocolDidFinishLoading:self];
    self.connection = nil;
}
@end

And now the interesting part - Modifying every request that goes to my server

So first: Check if this Request goes to my Server and determine if my protocol should take care of it

+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
    NSString *token = [[NSUserDefaults standardUserDefaults] stringForKey:kDefaultsKeyLoginToken];
    NSString *hash = [[NSUserDefaults standardUserDefaults] stringForKey:kDefaultsKeyLoginHash];
    if([NSURLProtocol propertyForKey:@"TokenSet" inRequest:request]) return NO; // We already handled it
    if((hash == nil) || (token == nil) ) return NO; // We are not logged in
    NSString *params = [NSString stringWithFormat:@"mobile=app&user_token=%@&user_hash=%@",token,hash];
    if (([[[request URL] absoluteString] rangeOfString:BASE_URL].location != NSNotFound) && ([[[request URL] absoluteString] rangeOfString:@"/assets/"].location == NSNotFound)){
            if([[[request URL] absoluteString] rangeOfString:params].location == NSNotFound){
                return YES; // URL does not contain the login token & we're not requesting an asset (js/img/etc.)
            }


    }
    return NO;
}

So if + (BOOL)canInitWithRequest:(NSURLRequest *)request returned yes, I have to handle the request. I already know that it does not contain the login token & hash so I've got to determine if it has to be appended or not. To modify the request in general, I create a MutableCopy of our request, Modify it and set our URLConnection to the request.

- (void)startLoading
{
    NSMutableURLRequest *newRequest = [self.request mutableCopy];
    NSString *PreURL;
    NSString *token = [[NSUserDefaults standardUserDefaults] stringForKey:kDefaultsKeyLoginToken];
    NSString *hash = [[NSUserDefaults standardUserDefaults] stringForKey:kDefaultsKeyLoginHash];
    NSString *params = [NSString stringWithFormat:@"mobile=app&user_token=%@&user_hash=%@",token,hash];
        if([[newRequest URL] query] == nil) {
            PreURL = [NSString stringWithFormat:@"%@?%@",[[newRequest URL] absoluteString],params];
        }else{
            if([[[newRequest URL] absoluteString] rangeOfString:params].location == NSNotFound){
                PreURL = [NSString stringWithFormat:@"%@&%@",[[newRequest URL] absoluteString],params];
            }
        }
    NSURL *nsurl = [NSURL URLWithString: PreURL];
    [newRequest setURL:nsurl];
    [NSURLProtocol setProperty:@"YES" forKey:@"TokenSet" inRequest:newRequest];
    self.connection = [NSURLConnection connectionWithRequest:newRequest delegate:self];



}

And to finish it all, we register our URL-Protocol as Protocol in AppDelegate.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [NSURLProtocol registerClass:[MyURL class]];
}

With this Solution I first have the advantage of having my login token in ANY request ANY part of my App sends to my Server. No more worries about this. And I can do cool stuff, like saving resources after loading them the first time or even use Images from my App-Bundle in Webviews...

I hope this helps someone.