URLs from youtube playlist in iOS app - ios

Question

I´m working on a class which retrieves links of a youtube playlist by using the YouTube Objective-C API.
Each URL is stored as a String strURL in an array called arrayURL, (for now) arrayURL is finally stored in arrayFinal, which I want to access from a different class.
Within the function I get the information I want (NSLog(#"%#", self.arrayFinal);). But when calling the function for example from another class (e.g. ViewController) I will always get an empty array back.
ViewController.m
YTDataHandler *youtubeObj = [YTDataHandler new];
[youtubeObj initYoutubeArray];
NSLog(#"%#", [youtubeObj arrayFinal]);
YTDataHandler.h
#import <Foundation/Foundation.h>
#interface YTDataHandler : NSObject
{
NSMutableArray *arrayFinal;
}
- (void)initYoutubeArray;
- (void)getYoutubeContent;
#property (nonatomic, retain) NSMutableArray *arrayFinal;
#end
YTDataHandler.m
#import "YTDataHandler.h"
#import "GTLServiceYouTube.h"
#import "GTLYouTube.h"
#import "GTLYouTubePlaylistSnippet.h"
#import "GTLYouTubeResourceId.h"
#implementation YTDataHandler
#synthesize arrayFinal;
- (void)initYoutubeArray {
self.arrayFinal = [[NSMutableArray alloc] init];
[self getYoutubeContent];
}
- (void)getYoutubeContent {
NSMutableArray *arrayURL = [[NSMutableArray alloc] init];
// Create a service object for executing queries
GTLServiceYouTube *service = [[GTLServiceYouTube alloc] init];
// API key
service.APIKey = #"YOUR_API_KEY";
// Create a query
GTLQueryYouTube *query = [GTLQueryYouTube queryForPlaylistItemsListWithPart : #"id, snippet, contentDetails"];
query.playlistId = #"UUa0XHGDbBL8re8UgO-OWNPA";
query.maxResults = 20;
query.type = #"video";
// Execute the query
GTLServiceTicket *ticket = [service executeQuery : query
completionHandler : ^(GTLServiceTicket *ticket, id object, NSError *error) {
// This callback block is run when the fetch completes
if (error == nil) {
GTLYouTubePlaylistItemListResponse *items = object;
// iteration of items and subscript access to items.
for (GTLYouTubePlaylistItem *item in items) {
// IDs of videos
NSString *strVideoId = [item.snippet.resourceId JSONValueForKey : #"videoId"];
// encode and extend the videoId, result as an URL
NSString *strEncoded = [strVideoId stringByAddingPercentEscapesUsingEncoding : NSUTF8StringEncoding];
NSString *strURL = [NSString stringWithFormat:#"http://www.youtube.com/watch?v=%#", strEncoded];
// store strURL
[arrayURL addObject : (#"%#", strURL)];
}
// finally store arrayURL
[self.arrayFinal addObject : (#"%#", arrayURL)];
NSLog(#"%#", self.arrayFinal);
} else {
NSLog(#"Error: %#", error);
}
}];
}
#end
What am I doing wrong in the // Execute the query-part?

Answer 1

In your view controller, when you make the call to getYoutubeContent on your YTDataHandler instance, you cannot expect the array to be immediately populated. It will be eventually populated when the query executes and the handler code is executed. In your handler code it always works because you are in the same thread, and you use arrayFinal when it is ready. In your view controller you need to wait until the array is ready, before you start using it. E.g. you could set a boolean flag on your YTDataHandler which your view controller can register a key-value observing callback (KVO), so that you can get automatically notified when the array is ready.
ps.
Why don't you use:
[arrayURL addObject: strURL];
instead of:
[arrayURL addObject : (#"%#", strURL)];
?