Beginning iOS Development
Chapter 26 — Property Lists (Obj-C)
- We have saved a string to the file system before. It worked like this.
- What would happen if we saved an array of strings? Let’s find out! (Could it be as simple as the same way we saved a string?)
- Yes! It was actually even simpler, there was no error object and encoding to deal with. So, how did it get saved? Here’s how.
- It got saved as a special XML document called a Property List, or plist for short.
- A plist can save lots of different kinds of data types.
- You can nest all of these in one plist. You could have an array of dictionaries, for instance. Here’s the example from the book.
- It’s an array of dictionaries that contain keys and values.
- Property Lists are very handy, iOS developers use them all the time for lots of purposes.
- Since they are just XML they are easy to make. We can just open any text editor and write them. However, Xcode makes it easier than that.
- When we create a new file with ⌘-N we can choose a Property List.
- After we name and save it, we will see the plist editor.
- We can choose an Array or a Dictionary as the root element of our document. I’ll choose Array for this demo.
- Click on the little plus symbol button to add a new element.
- We can set the data type for the new element to these types. I’ll choose Number
- Then you enter the value you want for the element.
- At any point you can use Xcode to view the XML source code of your plist file. Control-Click, or Right-Click the plist file name.
- Select Open As→Source Code and you will see the true content of the file.
- If you wanted to, you could make this a bigger list of integers with some text editing.
- Then switch back to the Property List view.
Reading a plist
- Now that we have a property list let’s read it back into a program.
- That’s it! If we display the array we get this.
- Yup, that’s an NSArray.