How to call a method after asynchronous task is complete
- by doctordoder
I have a class called WikiWebView which is a subclass of UIWebView which loads Wikipedia subjects and is designed to fetch all the links of the webpage, in order to create a sort of site map for the subject. My problem is that I can only create the links once the web page has loaded, but the loading isn't done right after [self loadRequest:requestObj] is called.
- (void)loadSubject:(NSString *)subject
{
// load the actual webpage
NSString *wiki = @"http://www.wikipedia.org/wiki/";
NSString *fullURL = [wiki stringByAppendingString:subject];
NSURL *url = [NSURL URLWithString:fullURL];
NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
[self loadRequest:requestObj];
// [self createLinks]; // need this to be called after the view has loaded
}
- (void)createLinks
{
NSString *javascript =
@"var string = \"\";"
"var arr = document.getElementsByClassName(\"mw-redirect\");"
"for (var i = 0; i < arr.length; ++i)"
"{"
"var redirectLink = arr[i].href;"
"string = string + redirectLink + \" \";"
"}"
"string;";
NSString *links = [self stringByEvaluatingJavaScriptFromString:javascript];
self.links = [links componentsSeparatedByString:@" "];
}
I tried the normal delegation technique, which lead to this code being added:
- (id)init
{
if (self = [super init])
{
self.delegate = self; // weird
}
return self;
}
#pragma mark - UIWebViewDelegate
- (void)webViewDidStartLoad:(UIWebView *)webView {
++_numProcesses;
}
- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
--_numProcesses;
}
- (void)webViewDidFinishLoad:(UIWebView *)webView {
--_numProcesses;
if (_numProcesses == 0) {
[self createLinks];
}
}
However, the delegate methods are never called..
I've seen similar questions where the answers are to use blocks, but how would I do that in this case?
