AES stands for Advanced Encryption Standard and is an industry-standard algorithm for encrypting data symmetrically which even the US government has approved for SECRET documents. If you don’t know what symmetrical encryption is, it means that you use the same key or password to encrypt the data as you do to unencrypt it. So you need to keep the key extremely secret however it’s still incredibly useful. I’ll show you how to use openssl to encrypt some data and decrypt it using the Common Crypto libraries on iOS.
I decided to go as a Ghostbuster for a fancy dress party recently. Of course all Ghostbusters need fully working Ghostbuster proton packs complete with animated LED displays and electroluminescent glowing wires, so here are the details on how I built mine. It took about 3 or 4 evenings to build and involved Arduinos, lots of hot glue and over 92 LEDs! It is just a shame I missed out on the best fancy dress award that night because it looked ‘too realistic’!
The Ghostbusters proton pack lit up in the dark
Example of rendered proportional numbers and monospaced numbers
Not all font instances are created equally! In iOS text is mostly displayed using proportional fonts, meaning each character width is trimmed and varies depending on each character. This makes the text easier to read and feel more natural and you’ll notice this on characters such as ‘i’ which will often be the thinnest character compared to say an ‘m’ character. However for numbers displayed in a tabular format such as times, figures and currencies you’ll want monospaced characters so you can tidy up the layout and visually scan the data quickly. So how do you do this?
Here’s a quick fire list of 5 time-saving Objective-C tips that every developer should know. Perfect for making time for that extra coffee!
1. Enum shorthand
Enums at their simplest are labelled sets of integers. Where an inexperienced programmer might use a number to represent the download state of an image lets say, e.g. 0 = queued, 1 = downloading, 2 = downloaded, 3 = complete… When using these numbers in actual code a simple slip of the finger on the keyboard and they could easily type an extra digit in their if statement or assignment. These types of errors don’t usually show up when compiling. Even worse, these are usually obscure errors that only reveal themselves at run-time and only then when things don’t work as expected often requiring considerable debugging effort.
This is where enums step in. Enums are really handy and allow you to associate symbols or ‘labels’ with integers. If you type an enum value that doesn’t exist the compiler steps in and reports an error at compile-time instead and Xcode will probably suggest a fix for you if it was a typo! The other benefit of enums is that you can quickly add new values into them and assuming your code doesn’t save the integer to disk your code will automatically work with the new values.
There are a couple of different ways to define enums but the easiest way which will also provide Xcode with some extra compiling hints is as follows: