Core Data can handle several versions of your Model. It’s easy to add a version (via Editor – Add Model Version) and set it active, but it’s not so easy to remove a version you no longer need. Thankfully there is a way to delete version files which goes a long way to declutter your […]
Your View Controllers are created by the Storyboard automatically depending their defined relationships in Interface Builder. Sometimes however we need to create and transition to View Controllers we’ve defined in code. For example, if you want to transition to a view as part of displaying a search result. We can do this by creating a […]
We’ve recently discussed how to deal with a Search Bar and Search Display Controller using Interface Builder. You can however do this in code too. This can be useful if you don’t want to make all the relevant connections in every Storyboard. This example assumes you have a Table View (self.tableView) to which you’d like […]
Both Cocoa and iOS have built-in methods to parse (and generate) JSON data using NSJSONSerialization. Most commonly you’ll want to call a URL with parameters which will return some data. You take this output and tell Objective-C that it’s JSON, then typecast the return to an array or a dictionary which in turn lets you […]
Just a quick reminder before I forget (again) how selectors are called: Some of Apple’s pre-written methods use whats known as a Selector. Here’s an example method that uses a selector: // create a bar button item UIBarButtonItem *linkButton = [[UIBarButtonItem alloc]initWithTitle:@”My Title” style:UIBarButtonItemStyleBordered target:self action:@selector(myMethod)]; Notice how the selector is created on the second […]
There’s a convenient method for that by the name of substringFromIndex. This example removes the first character: NSString *complete = @”12345″; NSString *cutOff = [complete substringFromIndex:1]; NSLog(@”%@”, cutOff); // cutOff is now 2345 substringFromString takes only one parameter which specifies where to start the new string. The first character is 0 based, like in arrays. […]
You can create Fetch Requests in the Xcode model editor, including a Predicate. These are somewhat easier to setup. To create one, select your .xcdatamodeld file, then head over to Editor – Add Fetch Request. Give it a catchy name and a filter property, and much of the above code becomes obsolete. Here’s how you […]
Retrieving Managed Objects is somewhat more complex than creating them, mainly because you can filter what you’re getting back rather than retrieve everything that your store file has to offer. Let’s first illustrate a basic NSFetchRequest. For the following examples I’m using the iOS Master/Detail template which provides an Entity called Event with a property […]
