24 Jan 2013

Connected Wellness: Threads, Cordova Lib, and Java to iOS

So it's been another eventful week for the Connected Wellness iOS team at CDOT. We've made a lot of progress towards having the project completed, but there are still some major outstanding issues that we need to tackle. The PacketParser has yet to be completed (one of the most complex portions of the plugin), we've still yet to hear back from A&D about low energy BT devices, which we need in order to use the CoreBluetooth framework provided by Apple, and we're still running into some problems regarding the amount of control that the CoreBT framework gives us. The CoreBT framework does not expose a way to start, stop, or enable Bluetooth in the device. These are all things that the Android plugin is able to do. Although it is not completely necessary to implement these (the user can start it manually) it would be nice to provide it to the user as a convenience.


To continue my discussion from last week in regards to the Invoker and dispatching Commands asynchronously on threads—it has been ridiculously easy to implement this. Instead of going through and creating our own WorkQueue and thread management classes I've implemented NSOperationQueue and NSInvocationOperation inside of the Invoker class. NSOperationQueue is provided by Apple and has all the functions to properly manage thread execution on a work queue and NSInvocationOperation allows us to specify the target and selector that the threads started from the work queue will invoke. Check out how easy it was to do here.

Cordova Lib

During this last week we ran into a big problem of everyone checking code into the repo that wasn't compiling or causing problems. Yesterday I went through and fixed all the compilation problems. We're planning to have a more strict review process in the future. One of the major problems that I encountered was the Cordova Lib not being properly compiled and linked to the project. This was caused because for some reason Cordova 2.0 doesn't support armv6, so I had to remove that from the Cordova project as well as the iOS port project. The other big issue is that currently the Cordova library is not included in the repository. This means that when a fresh copy is cloned you have to go through the process of manually downloading PhoneGap and incorporating it into the project. So in the next day or so I'm going to set up the repo to include the compiled archive and point the project to it by default.

Java to iOS

The other major problem that I ran into this week was specific to the port from Java to iOS. In the Java version the concrete commands reside as inner classes in the DevicePlugin class. Due to this they all have access to the BluetoothServer stored within the DevicePlugin class. Moving over to iOS we cannot use inner classes and so the commands need to be provided with access to the server in some other way. To compensate this I've introduced a new command, BluetoothCommand, which sits between the concrete commands and the ReturnableCommand. BluetoothCommand exposes the base plugin in the ReturnableCommand as a MedicalDevicePlugin as well as exposing a property on it to access the BluetoothServer on the MedicalDevicePlugin. You can check out that here. Now that I'm thinking about it a BluetoothCommand doesn't necessarily need to work with a MedicalDevicePlugin... what we'd need to do then in order to abstract it more is to create a base class like BluetoothPlugin that will expose a BluetoothServer property. I don't really know if we should do this though as I've read a lot recently about the dangers of over designing code. I'll post back next week about what comes from this.

Next Week

By the end of next week I'm hoping that we have most of the pieces in place to start testing. The PacketParser will be done and the few other commands that are left to be implemented will be done. Personally I will be working on some of the outstanding commands such as the listen and isSupported() commands.

- Tagged in cdot, seneca college, and open-source.

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Wow coding Copyleft Richard Eyre 2013

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