Retrieving latest version of component from within AppDelegate fails - ios

Question

I am pretty new to iOS development, and entered a position where I need to maintain a large existing project in obj-c.
I have a sidebar-menu which is a webview. When program starts it makes a url request to check whether there is a newer version of the menu, and in that case retrieves the latest version.
Right now when the app runs for the first time it shows the old version, and from the second time and on it shows the current version.
When I tried debugging I've seen that the method that compares between local and remote version gets an empty value for the remote version. As far as I can understand it, the url request for the latest version is async, and therefore the code continues to execute before the request returns the current version.
Following an answer from StackOverflow, I've tried to call the getDataConfiguration method from within viewDidLoad instead of from AppDelegate, but that didn't work.
Would appreciate any help!
relevant code:
AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { .
...
[DataManager getDataConfiguration:^(DataConfiguration *dataConfiguration, NSError *error) {
[AppData sharedInstance].dataConfiguration=dataConfiguration;
NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:dataConfiguration];
[standardDefaults setObject:encodedObject forKey:DATA_KEY];
[standardDefaults synchronize];
}];
[DataManager getProductMap:^(ProductsArray *products, NSError *error) {
[AppData sharedInstance].productsArray=products;
}];
DataManager.m
+(void)getDataConfiguration:(void (^)(DataConfiguration * dataConfiguration, NSError *error))completion
{
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
[manager GET:[Configuration sharedInstance].infoJSONURL parameters:nil progress:nil success:^(NSURLSessionTask *task, id responseObject) {
DataConfiguration * dataConfiguration = [DataConfiguration modelObjectWithDictionary:responseObject];
completion(dataConfiguration,nil);
} failure:^(NSURLSessionTask *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
}
+(void)updateHtmlFiles:(void (^)(NSError *error))completion{
float upToDateMenuVersion = [[AppData sharedInstance] dataConfiguration].general.menuVersion;
float localMenuVersion = [self getLocalMenuVersion];
if(upToDateMenuVersion != localMenuVersion){
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
manager.responseSerializer = [AFHTTPResponseSerializer serializer];
NSString *url = [NSString stringWithFormat:#"%#?v=%f", [Configuration sharedInstance].menuHTMLFileURL, [[NSDate new] timeIntervalSince1970]];
[manager GET:url parameters:nil progress:nil success:^(NSURLSessionTask *task, id responseObject) {
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
NSDictionary *htmlFiles = [userDefaults dictionaryForKey:#"HTML_FILES"];
NSMutableDictionary *mutableHtmlFiles = [NSMutableDictionary new];
NSString *myString = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];
[mutableHtmlFiles setValue:myString forKey:#"MENU"];
[userDefaults setObject:mutableHtmlFiles forKey:#"HTML_FILES"];
[self setLocalMenuVersion:upToDateMenuVersion];
completion(nil);
} failure:^(NSURLSessionTask *operation, NSError *error) {
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
NSDictionary *htmlFiles = [userDefaults dictionaryForKey:#"HTML_FILES"];
if(htmlFiles == nil){
NSString *menuFile = [[NSBundle mainBundle] pathForResource:#"menu" ofType:#"html"];
htmlFiles = #{#"MENU":[NSString stringWithContentsOfFile:menuFile encoding:NSUTF8StringEncoding error:nil]};
[userDefaults setObject:htmlFiles forKey:#"HTML_FILES"];
}
NSLog(#"Error: %#", error);
}];
}
}
+(void) setLocalMenuVersion: (float) version{
[[NSUserDefaults standardUserDefaults] setFloat:version forKey:#"menuVersion"];
}
+(float) getLocalMenuVersion {
return [[NSUserDefaults standardUserDefaults] floatForKey:#"menuVersion"];
}
Menu.m
- (void)viewDidLoad {
[super viewDidLoad];
_firstLoad = YES;
...
[self initWebView];
}
-(void) initWebView {
if(_webView == nil){
_webView = [[WKWebView alloc] initWithFrame:_webViewPlaceholder.frame];
[_webView.scrollView setZoomScale:3 animated:YES];
_webView.navigationDelegate = self;
_webView.UIDelegate = self;
NSString *javaScriptText = #"document.body.style.zoom = 3;";
[_webView evaluateJavaScript:javaScriptText completionHandler:nil];
[self.view addSubview:_webView];
_webView.scrollView.bounces = NO;
[self updateHtml];
[AppData updateHeaderAndMenu:^(NSError *error){
[self updateHtml];
}];
}
}
- (void)viewDidAppear:(BOOL)animated{
_webView.frame = CGRectMake(_webViewPlaceholder.frame.origin.x,_webViewPlaceholder.frame.origin.y, _webViewPlaceholder.frame.size.width, _webViewPlaceholder.frame.size.height);
}
-(void)updateHtml{
NSDictionary *htmlFiles = [AppData getHeaderAndMenu];
NSString *menu = [htmlFiles objectForKey:#"MENU"];
[_webView loadHTMLString:menu baseURL: [[NSBundle mainBundle] bundleURL]];
}
AppData.m
+(void)updateHeaderAndMenu:(void (^)(NSError *error))completion{
[DataManager updateHtmlFiles:completion];
}
ViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
...
[AppData updateHeaderAndMenu:^(NSError *error){ [self loadHeader]; }];
_firstLoad = YES;
...

Answer 1

The updateHeaderAndMenu method has a completion block which is called after the async operation completes without an error.
I'm assuming ViewController.m holds a reference to Menu?
If that is the case, viewDidLoad calls the updateHeaderAndMenu method and will execute the completionBlock (if there is no error). In this block I can already see that a method is called loadHeader. You could call [self.menu updateHtml]; there and this would probably work.
...
[AppData updateHeaderAndMenu:^(NSError *error){
[self loadHeader];
// [self.menu updateHtml];
}];
_firstLoad = YES;
...
I'm doing some guess work here but I think this would update your webview after the DataManager completes the http request.
Edit:
As to the order of execution. Here is a breakdown:
This is the method definition in AppData
+(void)updateHeaderAndMenu:(void (^)(NSError *error))completion{
[DataManager updateHtmlFiles:completion];
}
You can see completion (which is a block parameter) is passed on to the updateHtmlFiles method in DataManager:
+(void)updateHtmlFiles:(void (^)(NSError *error))completion{
...
completion(nil);
...
}
Eventually the completion parameter (which is a block) is called when the async http request completes. You can look at blocks as kind of inline methods which can be passed as a parameter. Google working with blocks ios to see the official Apple documentation for this.
So the order of execution is:
Menu calls updateHeaderAndMenu in AppData
which calls updateHtmlFiles in DataManager and passes on completion
http request completes and calls completion.
the content of the block is executed all the way back in Menu which is:
{
[self loadHeader];
// [self.menu updateHtml];
}
loadHeader is executed ...
If you want to get a better overview of what is called when, you can use breakpoints inside your code.