Monotouch is a C# development platform for iOs, the OS for iPhone, iPad and iPod touch. It runs on top of the Apple SDK, which includes device emulators to run and debug apps. For some time I’ve been working with it now, it has been a pleasure. Time to get my app out of the emulator and take it for a spin on a real iPhone.
It took some investments. The first one was a Mac, Monotouch only works on that. I had always liked the Mac, now I own one myself it rapidly took over as my main machine for everyday use. It’s hard to pinpoint what makes a Mac so pleasant to use; may I give one example ? Scrolling on a mac is done by swiping two fingers (over a gorgeous gigantic keypad), at first sight that works just like a scroll wheel. The nice thing is that it will scroll anything which is under the cursor, also when the window is not the active window. Marvelous when reading through a long webpage while trying to edit some enigmatic settings. The thing I still don’t like about the mac are the text navigation keys, where is the PgDn ? Any advice on that is appreciated.
Ok, so far, let’s get on topic again.
The free version of Monotouch only works with the emulator, you have to buy the professional version ($399) to be able to deploy to a physical device. The iPhone itself is quite protected, it will not allow anything which is not signed with a certificate issued by Apple. To obtain these certificates you have to join the Apple program which is another $99. Obtaining and installing all that and signing you app is quite a job. Marcus of LosTechies has a very good and clear post on how to do that. Just one comment on that, you have to fire up Xcode once before starting, otherwise it will not associate with the “provisioning profile”. Once you are part of the Apple program you can enroll up to 100 physical iOS devices. That will do.
And now I am really up and running. Connect the iPhone over USB, choose Debug (iPhone), set the breakpoints and you’re ready to peak into the inside of the phone.
Monotouch does a full persistent install of your app. Ready for a full field test.
Performance
The first thing I noticed with my app was performance. I have a modest Mac (the smallest Macbook pro) and a fast iPhone (4). Nevertheless the emulator completely outperforms the phone. Which forced me to try some optimizations. Which went quite successful. My app cycles through a lot of loops, what really helped a lot was switching from using foreach on a typed list to for on a typed array. A lot has been said on this when it comes to the different versions of the Windows .net framework. None of that applies to Monotouch. Monotouch is compatible at the source code level, when it comes to the binary part it is completely incomparable.
A small “wet-finger” test to demonstrate this.
A test class
public class MyClass
{
public MyClass()
{
AnInt = 1;
}
public int AnInt { get; private set;}
}
In a form both a list and an array of this class are instantiated.
public Form1()
{
InitializeComponent();
myClassList = new List<MyClass>();
myClassArray = new MyClass[itemCount];
for (int i = 0; i < itemCount; i++)
{
myClassList.Add(new MyClass());
myClassArray[i] = new MyClass();
}
}
const int itemCount = 25000;
List<MyClass> myClassList;
MyClass[] myClassArray ;
The click of a button touches all elements of the list and the array and times this
const int loopCount = 10000;
int dummy;
var start = DateTime.Now;
for (int i = 0; i < loopCount; i++)
for (int j = 0; j < itemCount; j++)
dummy = myClassArray[i].AnInt;
var stop = DateTime.Now;
var arrayTime = stop – start;
start = DateTime.Now;
for (int i = 0; i < loopCount; i++)
for (int j = 0; j < itemCount; j++)
dummy = myClassList[i].AnInt;
stop = DateTime.Now;
var listTime = stop – start;
label1.Text = listTime.ToString();
label2.Text = arrayTime.ToString();
Running this in a Windows application reveals that using an array is somewhere around 10% faster. Both in debug and release code. Release code is about 20% faster than debug code. This conforms to the public opinion on the matter.
This source code is easily ported to a Monotouch application. Resulting in
public partial class MyWindow : UIViewController
{
#region Constructors
// The IntPtr and initWithCoder constructors are required for items that need
// to be able to be created from a xib rather than from managed code
public MyWindow (IntPtr handle) : base(handle)
{
Initialize ();
}
[Export("initWithCoder:")]
public MyWindow (NSCoder coder) : base(coder)
{
Initialize ();
}
public MyWindow () : base(“MyWindow”, null)
{
Initialize ();
}
void Initialize ()
{
myClassList = new List<MyClass> ();
myClassArray = new MyClass[itemCount];
for (int i = 0; i < itemCount; i++) {
myClassList.Add (new MyClass ());
myClassArray[i] = new MyClass ();
}
}
#endregion
const int itemCount = 25000;
List<MyClass> myClassList;
MyClass[] myClassArray;
public override void ViewDidLoad ()
{
Button1.TouchDown+= delegate {
const int loopCount = 10000;
int dummy;
var start = DateTime.Now;
for (int i = 0; i < loopCount; i++)
for (int j = 0; j < itemCount; j++)
dummy = myClassArray[i].AnInt;
var stop = DateTime.Now;
var arrayTime = stop – start;
start = DateTime.Now;
for (int i = 0; i < loopCount; i++)
for (int j = 0; j < itemCount; j++)
dummy = myClassList[i].AnInt;
stop = DateTime.Now;
var listTime = stop – start;
Label1.Text = listTime.ToString ();
Label2.Text = arrayTime.ToString ();
};
base.ViewDidLoad ();
}
}
The main difference with a winform application is setting up the event-handler of the button click (TouchDown). This cannot be done until the view is loaded, you have to override ViewDidLoad to set it up.
Now we can run the same test on the iPhone emulator and the iPhone itself. This will show quite different figures. Both for the emulator versus the real phone and for debug versus release code.
| Debug | Release | |
| Emulator | 4:18 / 2:47 | 1:80/0:64 |
| iPhone | 57:00/46:00 | 16:70/7:20 |
The first time is the time using a list, the second time using an array. These timings do show
- Debug code has a big overhead
- Timings in the emulator do not predict timings on the phone
- It does pay of to use an array instead of a list. Over 100%
Winding down
The good thing with working with Monotouch is that it makes deploying and debugging real iPhone apps easy. It does also show where the pain points are. The main point to realize is that Monotouch looks and feels like the usual C# and .NET but is something completely different under the hood. We will see more of that in an upcoming post on submitting a Monotouch app to the AppStore.
