NSAssert is a macro which allows you to test for specific values if and when they occur. Rather than having to figure out where your app has passed the wrong value several stages before a problem happened, NSAssert can be used like NSLog – with the helpful difference that if all is well, there’s no […]
Sometimes Xcode just throws an error message that isn’t very helpful. That’s usually when we have to try and figure out why something didn’t go the way we expected it. Other times however, Xcode tells us very clearly which element it isn’t happy with – we fix it and our app progresses. Why can’t it […]
We can do this two ways: // version 1: [self.searchBar becomeFirstResponder]; // version 2: [self.searchDisplayController setActive:YES animated:YES]; The benefit of version 2 is that if we perform it “in vision”, we can use the animated option and make it look all swish. Version 2 of course also has a reverse with which we can deactivate […]
We can use substringWithRange for this, which requires us to define a range: NSString *something = @”123456789″; NSRange myRange = NSMakeRange(2, 3); something = [something substringWithRange:myRange]; // something is now 345 You create a range by specifying where the substring should start (the first character is 0, like in an array), then specify how many […]
We can use the substringToIndex method for this, using the length of our original string minus 1: NSString *something = @”12345″; something = [something substringToIndex:(something.length – 1)]; // something is now 1234
With typedef you can specify custom variable types. Instead of having a variable such as int, you could create your own – such as yourInt: // create a typedef of int typedef int yourInt; yourInt yourValue = 57; NSLog(@”Your value is %i”, yourValue); Now you have your own variable type called youInt which behaves just […]
An Enumeration (enum) allows you to create a collection of custom values. These can be more meaningful than simply using numbers. Imagine you want to track drink sizes, such as small, medium and large. You can remember to just use the numbers 1, 2 and 3 for each size – but Enumeration makes it easier […]
On occasion we need to create an NSIndexPath manually, with components we specify (such as a row or a section). There’s a method for that: indexPath:forItem:inSection. Here’s how you create an indexPath for row 0, section 0: NSIndexPath *indexPath = [[NSIndexPath alloc]init]; indexPath = [NSIndexPath indexPathForItem:0 inSection:0]; The method takes two integers. You can even […]
