I've decided to dabble a bit in MonoDroid and MonoTouch and port one of my WP7 apps as a starter. I would really like to reuse my existing ViewModels but since both Android and iOS seem to have no such thing as XAML's strong databinding I would like to ask if anyone went that route before and can recommend some best practices or existing solutions.
We're doing this with an application right now, but writing for iOS first (even before Windows). It is not full of rainbows and ponies for sure.
I would recommend the following:
Use a MVVM framework on Windows that doesn't require you to expose ICommand on every action the user takes (like Caliburn, for example), it also shouldn't require a dependency to it from within all of your ViewModels.
Conditionally inherit the WPF-specific pieces of your ViewModelBase class, you can do this with partial classes or an #if iPhone directive. INotifyPropertyChanged or ICommand are examples.
Use an IoC container, it is very helpful to abstract out things like saving settings to the filesystem which will be very different on all platforms. Also helps to sort out your dependencies as well, which is very helpful for separating out platform-specific code from non-platform specific.
Use a "messenger" of some kind (example here), usually included with an MVVM framework. This is a must in my opinion, at least for iOS. Apple's MVC is so all over the place, it's better to have global messages you can subscribe to in a weak referenced (and decoupled) way.
Use MVC on each platform like you would natively, then treat each ViewModel as you would if you were calling it manually. There are no UI bindings, no ICommand, so keep your ViewModel's simple.
Linking files is the best trick ever. You don't want a copy of each view model per platform, so make sure you know how to link to a file within projects in Visual Studio and MonoDevelop. This also makes #if iPhone and #if Android statements possible.
I know you are working with an existing application, so it's tough. It may be simpler to just reuse your business model and that's it. Android and iOS have MVC patterns of their own, and are drastically different from WPF. You might also only need a subset of each ViewModel on mobile devices, which could make it easier to just rewrite.
In our case:
We're using TinyIoC (also has it's own messenger)
We will use Caliburn-Micro when we start on WPF, we don't need some of the features in full Caliburn
I've recently finished a large project which we wrote wp7 first, and which was then ported into touch and droid.
As part of this we've released our own mvvm framework - including some databinding support for touch and droid - the source is available at http://github.com/slodge/mvvmcross
The experience of porting to droid was good - the axml layout files provided a good hook for databinding. Currently, however, i'm not quite as happy with the binding we achieved for touch - although montouch.dialog does at least provide us with some nice looking code sometimes.
Related
I have seen this question What is the difference between a class library and a framework
and throughout all the provided answers, the framework is always referenced as a framework. I am looking to get more technical. What exactly is a framework? A class of classes that control all functionality and provide ultimate abstraction and the ability to customize it? I am just looking to understand what exactly a framework is, as far as initializing it, not just what it accomplishes, but how exactly it is implemented. How I believe it's used/implemented is listed below.
variable = Framework() -> Reference the variable
Framework is an infrastructure, ready-made and predefined, with some particular rules of the game on the "development field", according to which, you can build your application, on top of it, by "playing with framework rules" (you can, at some extent, customize those rules).
Spring MVC is a good example of Framework. You don't control how the View Resolving, Dispatching or Template Rendering happen and achieve a goal together.
Think of this as a big machine, where you can plug in and integrate your components which are applicable to that machine.
Library, on the other hand, is just a set of classes, which provide already implemented functionality out of the box, in order to not start inventing the bicycle again and again.
Apache Commons is a good example of the Library. It has a lot of ready tools and functionality to facilitate your work with String objects.
Think of this as a set of instruments and tools, using which, you can build your own machine.
With respect to how it is implemented question. This is like asking how the Boeing A220 is built?. I'm not sure anyone can describe here how the Framework is implemented in the details. But if I understood uour point about whether the Framework is used via classes, then:
Framework might provide some classes as an abstraction, yes, but it's not about them, it's more about mechanics of the entire system. The main thing it provides is the mechanism and mechanics of how the system is designed to work.
I'm building a workbench/IDE style application which uses MEF to locate and load tools into the workbench at start up.
I'm using MVVM Light to build the workbench and the separate tools. I've got a point now where I want tools to be able to communicate which each other and the workbench.
I don't mean direct communication, more like "Hey I have some data here if anyone's interested" and interested tools can pick up the data.
This looks much like C# events and I know I can export an interface from my tool(s) which defines the event(s) but I'm also wondering about using the MVVM Light messenger to provide the communication.
I've seen on here that people are using the EventAggregator from Prism to do the same thing and as the messenger from MVVM Light is roughly analogous I figured I could use it.
I'm after advice really, has anyone used the messenger for MEF - MEF object and would you advocate it over plain old C# events.
What you are looking at here is the mediator pattern. You could use plain old C# events to do the same thing... but do to it right you would most likely end up implementing your own kind of pub/sub pattern. And if you are going to do that, why re-invent the wheel?
I like using prism's EventAggregator because it is part of the Prism framework injected with MEF. I use a lot of other things from Prism, so it's nice to get this for 'free'. It also promotes loose coupling with your components, and like all of the good mediator implementations it is implemented with the weak event pattern which prevents the memory issues you would need to avoid yourself when destroying objects that have subscribed to an event.
For what it's worth, I used to use MVVM Light, but I found Prism to be a more mature framework, with better documentation, examples and a larger user base to learn from. That's really just my opinion- I know loads of people who love MVVM Light. Play with them both and pick the one that makes you happy :)
I am about to start building an app that will be used across all platforms. I will using monotouch and monodriod so I can keep things in .net
I'm a little lazy so I want to be able to reuse as much code as possible.
Lets say I want to create an application that stores contact information. e.g. Name & Phone number
My application needs to be able to retrieve data from a web service and also store data locally.
The MVVM pattern looks like the way to go but im not sure my approach below is 100% correct
Is this correct?
A project that contains my models
A project that contains my views,local storage methods and also view models which I bind my views to. In this case there would be 3 different projects based on the 3 os's
A data access layer project that is used for binding to services and local data storage
Any suggestions would be great.
Thanks for your time
Not specifically answering your question, but here are some lazy pointers...
you can definitely reuse a lot of code across all 3 platforms (plus MonoWebOS?!)
reusing the code is pretty easy, but you'll need to maintain separate project files for every library on each platform (this can be a chore)
MVVM certainly works for WP7. It's not quite as well catered for in MonoTouch and MonoDroid
some of the main areas you'll need to code separately for each device are:
UI abstractions - each platform has their own idea of "tabs", "lists", "toasts", etc
network operations - the System.Net capabilities are slightly different on each
file IO
multitasking capabilities
device interaction (e.g. location, making calls etc)
interface abstraction and IoC (Ninject?) could help with all of these
The same unit tests should be able to run all 3 platforms?
Update - I can't believe I just stumbled across my own answer... :) In addition to this answer, you might want to look at MonoCross and MvvmCross - and no doubt plenty of other hybrid platforms on the way:
https://github.com/slodge/MvvmCross
http://monocross.net (MVC Rather then Mvvm)
Jonas Follesoe's cross platform development talk: Has to be the most comprehensive resource out there at the moment. He talks about how best to share code and resources, abstract out much of the UI and UX differences, shows viable reusable usage of MVVM across platforms and nice techniques for putting together an almost automated build. (yes, that includes a way for you to compile you monotouch stuff on Visual Studio)
Best of all he has a available source code for the finished product and for a number of the major component individually placed in its own workshop project and a 50 + page pdf detailing the steps to do so.FlightsNorway on github
IMO the only thing missing is how best to handle local data storage across all platforms. In which case I would direct you to Vici Cool Storage an ORM that can work with WP7, MonoTouch and (while not officially supported) MonoDroid.
*Disclaimer* The site documentation isn't the most updated but the source code is available. (Because documentation is Kriptonite to many a programmer)
I think the easiest way to write the code once and have it work on all three platforms will probably be a web-based application. Check out Untappd for example.
You can start by looking at Robert Kozak's MonoTouch MVVM framework. It's just a start though.
MonoTouch MVVM
What are the advantages of using Framework over Library or other way around while developing Web Applications or different types of Software.
I understand using Framework we can make use of basic functionality and then add upon functionality which we require but I am having hard time understanding the advantages of it as if we develop using Library than also we get some basic functionality and then add upon them the functionality as we need and so where in comes the actual advantages of using Framework.
I think it's important to distinguish between a framework and a library when answering.
A framework follows the Hollywood principle: "Don't call us; we'll call you." You plug your code into the framework according to its API. The framework acts as a constraint that solves the particular problem it was designed to solve (e.g., web application development).
A framework will use a combination of your code and 3rd party libraries to solve a particular problem. It will treat your code as one of those 3rd party libraries.
If you eschew a framework, the roles are reversed. Now you and your code are in charge: "I'll do the calling, thank you." A library is a self-contained piece that plugs into the software that you write.
So why prefer a framework? Use one that is written better than the scaffolding that you would be able to write yourself. A framework is likely to be tested more thoroughly and have a wider user base than code you'll write.
You'd write an application without a framework if you're working on a specialized problem, you have deep knowledge of the domain, and there are no frameworks available that demonstrate deeper insight than you have.
A library is just something that solves a problem but it is your job to integrate it the project. Basically it offers some feature that are context-free.
A framework will provide the features plus an infrastructure for them - you will have to develop according to the framework's rules. So you might have less control and freedom but you save time.
I have a set of functionality (classes) that I would like to share with an application I'm building for the iPhone and for the Blackberry (Java). Does anyone have any best practices on doing this?
This is not going to be possible as far as I understand your question - the binary format for the iPhone and Java are not compatible - and even for a native library on a blackberry device.
This is not like building for OS X where you can use Java unfornately the iPhone doesn't support Java.
The best idea is probably to build you library in Objective-C and then port it to Java which is an easier transition than going the other way. If you programme for Objective-C and make sure you code has no memory leaks - then the changes are not so complex.
If you keep the structure of your classes the same then you should find maintenance much simpler - fix a bug in the Java and you should find it easy to check for the same bug in the ObjC methods etc.
Hope this helps - sorry that it is not all good news.
As Grouchal mentioned - you are not going to be able to share any physical components of your application between the two platforms. However you should be able to share the logical design of your application if you carefully separate it into highly decoupled layers. This is still a big win because the logical application design probably accounts for a large part of your development effort.
You could aim to wrap the sections of the platform specific APIs (iPhone SDK etc.) that you use with your own interfaces. In doing so you are effectively hiding the platform specific libraries and making your design and code easier to manage when dealing with differences in the platforms.
With this in place you can write your core application code so that it appears very similar on either platform - even though they are written in different languages. I find Java and Objective-C to be very similar conceptually (at least at the level at which I use it) and would expect to be able to achieve parity with at least the following:
An almost identical set of Java and Objective-C classes with the same names and responsibilities
Java/Objective-C classes with similarly named methods
Java/Objective-C methods with the same responsibilities and logical implementations
This alone will make the application easier to understand across platforms. Of course the code will always look very different at the edges - i.e when you start dealing with the view, threading, networking etc. However, these concerns will be handled by your API wrappers which once developed should have fairly static interfaces.
You might also stand to benefit if you later developer further applications that need to be delivered to both platforms as you might find that you can reuse or extend your API wrappers.
If you are writing a client-server type application you should also try and keep as much logic on your server as possible. Keep the amount of extra business logic on the device to a minimum. The more you can just treat the device as a view layer the less porting you'll have to do over all.
Aside from that, following the same naming conventions and package structure across all the projects helps greatly, especially for your framework code.
The UI API's and usability paradigms for BlackBerry and iPhone are so different that it won't be possible in most cases to directly port this kind of logic between apps. The biggest mistake one could make (in my opinion) is to try and transplant a user experience designed for one mobile platform on to another. The way people interact with BlackBerrys vs iPhones is very different so be prepared to revamp your user experience for each mobile platform you want to deploy on.
Hope this is helpful.
It is possible to write C++ code that works in both a BB10 Native app and an iOS app.
XCode would need to see the C++ files as ObjectiveCPP code.
I am currently working on such a task in my spare time. I have not yet completed it enough to either show or know if it is truly possible, but I haven't run in to any road-blocks yet.
You will need to be disciplined to write good cross-platform code designed w/ abstractions for platform-specific features.
My general pattern is that I have "class Foo" to do cross platform stuff, and a "class FooPlatform" to do platform specific stuff.
Class "Foo" can call class "FooPlatform" which abstracts out anything platform specific.
The raw cross-platform code is itself not compile-able on its own.
Separate BB10 and XCode projects are created in their respective IDEs.
Each project implements a thin (few [dozen] line) "class FooPlatform" and references the raw cross-platform code.
When I get something working that I can show I will post again here...