Refine Mobile Services queries with paging

PLATFORM

iOSWindows Store C#Windows Store JavaScriptWindows PhoneAndroidXamarin iOSXamarin AndroidHTMLiOS

BACKEND

Select...JavaScriptJavaScript

This topic shows you how to use paging to manage the amount of data returned to your iOS app from Azure Mobile Services. In this tutorial, you will use the fetchLimit and fetchOffset query properties on the client to request specific "pages" of data.

NOTE

To prevent data overflow in mobile device clients, Mobile Services implements an automatic page limit, which defaults to a maximum of 50 items in a response. By specifying the page size, you can explicitly request up to 1,000 items in the response.

This tutorial builds on the steps and the sample app from the previous tutorial Get started with data. Before you begin this tutorial, you must complete at least the first tutorial in the working with data series, Get started with data.

1. In Xcode, open the project that you modified when you completed the tutorial Get started with data.
2. Press the Run button (Command + R) to build the project and start the app, then enter text into the textbox and click the plus (+) icon.
3. Repeat the previous step at least three times, so that you have more than three items stored in the TodoItem table.
4. Open the QSTodoService.m file, and locate the following method:

   - (void)refreshDataOnSuccess:(QSCompletionBlock)completion

   Replace the body of the entire method with the following code.

   // Create a predicate that finds active items in which complete is false
   NSPredicate * predicate = [NSPredicate predicateWithFormat:@"complete == NO"];
   
   // Retrieve the MSTable's MSQuery instance with the predicate you just created.
   MSQuery * query = [self.table queryWithPredicate:predicate];
   
   query.includeTotalCount = YES; // Request the total item count
   
   // Start with the first item, and retrieve only three items
   query.fetchOffset = 0;
   query.fetchLimit = 3;
   
   // Invoke the MSQuery instance directly, rather than using the MSTable helper methods.
   [query readWithCompletion:^(NSArray *results, NSInteger totalCount, NSError *error) {
   
       [self logErrorIfNotNil:error];
       if (!error)
       {
           // Log total count.
           NSLog(@"Total item count: %@",[NSString stringWithFormat:@"%zd", (ssize_t) totalCount]);
       }
   
       items = [results mutableCopy];
   
       // Let the caller know that we finished
       completion();
   }];

   This query returns the top three items that are not marked as completed.
5. Rebuild and start the app.
   Notice that only the first three results from the TodoItem table are displayed.
6. Update the refreshDataOnSuccess method once more by locating the following line of code:

   query.fetchOffset = 0;

   This time, set the query.fetchOffset value to 3.
   This query skips the first three results and returns the next three after that. This is effectively the second "page" of data, where the page size is three items.
   NOTE

   This tutorial uses a simplified scenario by setting hard-coded paging values for the fetchOffset and fetchLimitproperties. In a real-world app, you can use queries similar to the above with a pager control or comparable UI to let users navigate to previous and next pages. You can also set **query.includeTotalCount = YES** to get the total count of all items available on the server, along with the paged data.

Source from

http://azure.microsoft.com/en-us/documentation/articles/mobile-services-ios-add-paging-data/