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 […]
Assuming you’re using an app template that includes Core Data, you will have access to the Managed Object Context. In the simplest form, and without custom Entity classes setup, you can use key/value coding to set your object’s properties. In fact, the Master/Detail template does this. Here’s an example for an Entity named Event with […]
Likewise we can save our previously selected file using an NSSavePanel. It too is easy to use, just as the NSOpenPanel. For a save action to make sense we need to have some data to save, so in this example we will copy an existing file (self.myURL) to the new URL that the save panel […]
NSOpenPanel is surprisingly easy to use: create the panel, call the openPanel method, and handle the returned URL object in a block. In this example we invoke the panel from a button in the main window, then display the returned URL in a textLabel: – (IBAction)loadFile:(id)sender { // create an open documet panel NSOpenPanel *panel […]
