KnOwledge

Transcription

1 RoCk SOLiD KnOwledge David Wheeler Designing UIs with the Composite Application Guidance 2009 RoCk SOLid KnOwledge 1

2 Agenda Background to composite applications Overview of Prism v2 for WPF Hopefully not too many slides 2009 RoCk SOLid KnOwledge 2

3 Composite applications Challenges for enterprise application developers Enterprise applications can get messy - fast long-lived, new pieces being added all the time multiple development teams varied sources of data poor separation of concerns / close coupling difficulties in testing 2009 RoCk SOLid KnOwledge 3

4 Composite applications What is a composite application? unified composite legacy legacy services services 2009 RoCk SOLid KnOwledge 4

5 Composite applications Composition is also present in the UI UI built using composition Shared services e.g. logging logger Loosely coupled communication required between components e.g. Save All command 2009 RoCk SOLid KnOwledge 5

6 Composite applications Prism v2 Published by MS Patterns & Practices Group Guidance on how to create composite apps reference application how to and documentation Composite Application Library (CAL) WPF/Silverlight replacement for CAB still consider CAB for mixed-mode apps See microsoft.com/compositewpf 2009 RoCk SOLid KnOwledge 6

7 Prism v2 Focus on WPF Utilises core features of WPF data binding for view <-> viewmodel ICommand implementation for commands Lightweight inheritance footprint views are just standard user controls shell is just a normal WPF Window (typically) 2009 RoCk SOLid KnOwledge 7

8 Prism v2 Core parts Dependency Injection container Bootstrapper Shell Modules Views Services 2009 RoCk SOLid KnOwledge 8

9 Dependency Injection DI (or IoC) used to create objects register types / instances with container can be done using configuration or code clients can query the container for objects DI container can inject objects as needed largely done using.ctor injection in Prism Default container in Prism is Unity roll your own by implementing IUnityContainer 2009 RoCk SOLid KnOwledge 9

10 Dependency Injection public class TypeB { public TypeB( TypeA a ) {... } } Container Register () TypeA TypeB Container Resolve<TypeB>() B A 2009 RoCk SOLid KnOwledge 10

11 Bootstrapper Bootstrapper needed when DI is in use gets the application started Prism provides a UnityBootstrapper prepares the default services used by Prism e.g. logging, region management Typically created in App s OnStartup method 2009 RoCk SOLid KnOwledge 11

12 Bootstrapper Application start-up sequence App OnStartUp Bootstrapper Run Configure container Configure core services Create shell Configure region mappings Initialise modules 2009 RoCk SOLid KnOwledge 12

13 Shell Shell provides the main window for the app typically hosts one or more regions Shell ToolbarRegion InfoRegion MainRegion 2009 RoCk SOLid KnOwledge 13

14 Regions Regions are named placeholders views are activated within a region controlled using a RegionManager Regions are set with an attached property RegionManager.RegionName Regions can be content controls (notionally a single active view) items controls (such as TabControl) 2009 RoCk SOLid KnOwledge 14

15 Regions <!-- Within the Shell.xaml file --> <TabControl xmlns:cal= cal:regionmanager.regionname= MainRegion />... <ContentControl xmlns:cal= cal:regionmanager.regionname= EditorRegion /> RoCk SOLid KnOwledge 15

16 Composite applications Modularity Ideally break applications into modules e.g. HR module, payroll module, sales module Module can contain multiple views / services HR Payroll Sales Logger Modules Common 2009 RoCk SOLid KnOwledge 16

17 Modules Modules implement the IModule interface single Initialize() method akin to entry point Typically creates the services / views it needs Uses.ctor injection for two key items IUnityContainer for registering services IRegionManager for working with regions Stick to one module per assembly 2009 RoCk SOLid KnOwledge 17

18 Modules public class HRModule : IModule { IRegionManager regionmanager; IUnityContainer unitycontainer; public HRModule( IUnityContainer unitycontainer, IRegionManager regionmanager ) { this.unitycontainer = unitycontainer; this.regionmanager = regionmanager; } } public void Initialize() { // register services // create views / view models } 2009 RoCk SOLid KnOwledge 18

19 Module loading Modules are stored in a catalogue created by the Bootstrapper Can locate modules a number of ways code-driven catalog (easiest, least flexible) XAML-driven configuration-driven directory-driven (ultimate in dynamism) custom 2009 RoCk SOLid KnOwledge 19

20 Module loading Modules can be loaded at startup on demand Modules can depend upon other modules ensures loading in the correct sequence 2009 RoCk SOLid KnOwledge 20

21 Module catalogues public class Bootstrapper : UnityBootstrapper { protected override IModuleCatalog GetModuleCatalog() { ModuleCatalog catalog = new ModuleCatalog(); catalog.addmodule( typeof( MessagingModule ) ); catalog.addmodule( typeof( HRModule ) ); catalog.addmodule( typeof( PayrollModule ), HRModule ); return catalog; } } protected override DependencyObject CreateShell() {... } 2009 RoCk SOLid KnOwledge 21

22 Views Views are placed in regions composite views themselves define more regions Represent a portion of the UI for a module Typically created through two approaches View first - views created by module Presenter first - views injected into view model 2009 RoCk SOLid KnOwledge 22

23 Views More often than not, a simple UserControl can be a template, custom control, etc. key is that there is no inheritance constraint Organise your project to support views place them in a Views folder in your module Use binding to populate their data also use binding to set commands 2009 RoCk SOLid KnOwledge 23

24 View <-> Model <-> ViewModel Prism tends to use V-M-VM pattern View ViewModel Model Data-bound UI Data-bound properties Commands Service calls Data access 2009 RoCk SOLid KnOwledge 24

25 Creating views public class HRModule : IModule { IRegionManager regionmanager;... // regionmanager injected using DI container } public void Initialize() { HRMainView view = new HRMainView(); IRegion region = regionmanager.regions[ MainRegion ]; region.add( view ); region.activate( view ); } 2009 RoCk SOLid KnOwledge 25

26 Services Services!= Web Services (well, not ALL the time, anyway) Module registers service with DI container consumers can then resolve service as needed Some services are common across modules create in an infrastructure module 2009 RoCk SOLid KnOwledge 26

27 Services Logging service Prism provides a default logging mechanism via the ILoggerFacade interface can use any logging architecture e.g. log4net, Ent Lib logging block, etc RoCk SOLid KnOwledge 27

28 Consuming services public class HRModule : IModule { IUnityContainer unitycontainer;... // unitycontainer injected using DI container } public void Initialize() {... ILoggerFacade logger = unitycontainer.resolve<iloggerfacade>(); logger.log("hey, I've been logged", Category.Info, Priority.Low); } 2009 RoCk SOLid KnOwledge 28

29 Commands Background WPF has a strong command mechanism routed commands and ICommand A couple of important limitations focus (logical) and otherwise is problematic command bindings often have to be set at root doesn t do Save All functionality well 2009 RoCk SOLid KnOwledge 29

30 Commands Invoker ICommand Real Command Receiver 2009 RoCk SOLid KnOwledge 30

31 Commands Prism commands Prism provides custom command types DelegateCommand CompositeCommand Commands typically bound to view controls commands are exposed by ViewModel 2009 RoCk SOLid KnOwledge 31

32 Commands A simple DelegateCommand <Button Command= {Binding Path=Search} CommandParameter= {Binding Path=EmployeeName, Mode=TwoWay} Content= Search /> public class HRViewModel { public DelegateCommand<string> Search { get; private set; } public HRViewModel() { Search = new DelegateCommand<string>( OnSearch, OnCanSearch ); } void OnSearch( string employeename ) {... } } bool OnCanSearch( string employeename ) {... } 2009 RoCk SOLid KnOwledge 32

33 Commands CompositeCommand Save All Save Save Save 2009 RoCk SOLid KnOwledge 33

34 Commands A simple CompositeCommand public static class GlobalCommands { public static CompositeCommand SaveAllCommand = new CompositeCommand(); } public class HRViewModel { public DelegateCommand<string> Save { get; private set; } } public HRViewModel() { Save = new DelegateCommand<string>( OnSave, OnCanSave ); GlobalCommands.SaveAllCommand.RegisterCommand( Save ); } RoCk SOLid KnOwledge 34

35 Commands Proxying composite commands Code on previous slide a bit icky hard dependency on the GlobalCommands class Prefer to proxy the global command register a service with the DI container enables the command to be mocked out 2009 RoCk SOLid KnOwledge 35

36 Events Routed events not reliable for composites only bubble up the visual tree Modules need a way to communicate commands are do it now events are hey, you might be interested CAL contains a pub/sub event aggregator 2009 RoCk SOLid KnOwledge 36

37 Events Modularity Publisher Sales Subscriber Finance Event 2009 RoCk SOLid KnOwledge 37

38 Events A simple event public class OrderPlacedEvent : CompositePresentationEvent<OrderInfo> {} public class OrderInfo {... } EventAggregator agg = unitycontainer.resolve<eventaggregator>(); OrderPlacedEvent evt = agg.getevent<orderplacedevent>(); evt.publish( new OrderInfo() {... } ); EventAggregator agg = unitycontainer.resolve<eventaggregator>(); OrderPlacedEvent evt = agg.getevent<orderplacedevent>(); evt.subscribe( o => DataContext = o, ThreadOption.UIThread, false ); 2009 RoCk SOLid KnOwledge 38

39 Summary Learning curve relatively shallow However... you need to buy into DI you need to be comfortable with binding in WPF discipline is key to success might still need CAB for mixed WPF/WinForms 2009 RoCk SOLid KnOwledge 39

40 Summary Prism v2 offers solid guidance addresses common architectural challenges supports WPF and Silverlight extensible minimal inheritance enforcement commands and events good in themselves Get the bits RoCk SOLid KnOwledge 40

41 RoCk SOLiD KnOwledge Thanks for coming Q & A 2009 RoCk SOLid KnOwledge 41