I want to implement fluent api to my mvc sites. I got the basics.
So implement object library such as:
public class UIElement{/*...*/}
public class ButtonBase : UIElement{/*...*/}
public class LinkButton : ButtonBase {/*...*/}
public static class Extensions
{
public static T UIElementMethod<T>(this T element, string title)
where T : UIElement
{
return element;
}
public static T ButtonBaseMethod<T>(this T element, string title)
where T : ButtonBase
{
return element;
}
public static T LinkButtonMethod<T>(this T element, string title)
where T : LinkButton
{
return element;
}
}
But how to use it in razor view without some flush method calling.
#Html.UIproject().LinkButton()
.UIElementMethod("asd")
.ButtonBaseMethod("asd")
.LinkButtonMethod("asd")
But it returns the name of the class. I tried to make an implicit operator to MvcHtmlString but it's not called.
Any idea how to achieve this. How to know it's the and of the chain. I like the way how the Kendo UI work.
Thanks,
Péter
Your UIElement classes need to implement the IHtmlString interface. This interface's ToHtmlString method gets called by Razor and should return an HTML-encoded string.
So I would implement this on the abscract base UIElement and create RenderHtml method which can be implemented by the concrete LinkButton, etc. classes:
public abstract class UIElement : IHtmlString
{
public string ToHtmlString()
{
return RenderHtml(); // This should return an HTML-encoded string.
}
public override string ToString()
{
return ToHtmlString();
}
protected abstract string RenderHtml();
}
If you check KendoUI in Reflector/JustDecompile/dotPeek in the WidgetBase class you will see the same pattern.
I haven't tried it, in this particular situation, but you might be able to use an implicit cast to convert from a fluent builder to the object you need (see this blog).
Related
I have a class (OmeletteMaker) that contains an injected field (Vegetable). I would like to write a producer that instantiates an injected object of this class. If I use 'new', the result will not use injection. If I try to use a WeldContainer, I get an exception, since OmeletteMaker is #Alternative. Is there a third way to achieve this?
Here is my code:
#Alternative
public class OmeletteMaker implements EggMaker {
#Inject
Vegetable vegetable;
#Override
public String toString() {
return "Omelette: " + vegetable;
}
}
a vegetable for injection:
public class Tomato implements Vegetable {
#Override
public String toString() {
return "Tomato";
}
}
main file
public class CafeteriaMainApp {
public static WeldContainer container = new Weld().initialize();
public static void main(String[] args) {
Restaurant restaurant = (Restaurant) container.instance().select(Restaurant.class).get();
System.out.println(restaurant);
}
#Produces
public EggMaker eggMakerGenerator() {
return new OmeletteMaker();
}
}
The result I get is "Restaurant: Omelette: null", While I'd like to get "Restaurant: Omelette: Tomato"
If you provide OmeletteMaker yourself, its fields will not be injected by the CDI container. To use #Alternative, don't forget specifying it in the beans.xml and let the container instantiate the EggMaker instance:
<alternatives>
<class>your.package.path.OmeletteMaker</class>
</alternatives>
If you only want to implement this with Producer method then my answer may be inappropriate. I don't think it is possible (with standard CDI). The docs says: Producer methods provide a way to inject objects that are not beans, objects whose values may vary at runtime, and objects that require custom initialization.
Thanks Kukeltje for pointing to the other CDI question in comment:
With CDI extensions like Deltaspike, it is possible to inject the fields into an object created with new, simply with BeanProvider#injectFileds. I tested this myself:
#Produces
public EggMaker eggMakerProducer() {
EggMaker eggMaker = new OmeletteMaker();
BeanProvider.injectFields(eggMaker);
return eggMaker;
}
Using Guice,I would like create three different instances for my Color class i.e BLUE, RED, YELLOW and want to bind different color value... but I am not understanding how to bind different value per instance...
For the below sample code, if you see, I would like to use same ColorClass implementation for all three colors Instances(named as "BLUE","RED","ORANGE") by passing different color as String variable.
public interface ColorInterface {
public String getMeColor()
}
Sample implementation....
public class ColorClass implements ColorInterface {
#Inject #Named("color")
String color
public String getMeColor(){
return color
}
}
Sample binding........
public class ColorModule extends AbstractModule {
#Override
protected void configure() {
bind(ColorInterface.class).annotatedWith(Names.named("BLUE")).to(ColorClass.class);
bind(ColorInterface.class).annotatedWith(Names.named("RED")).to(ColorClass.class);
bind(ColorInterface.class).annotatedWith(Names.named("ORANGE")).to(ColorClass.class);
......
}
}
Please help me...
If this directly is your issue, I would suggest a slight change in the implementation to move the injected #Named("color") String into a constructor argument and the use of a custom Provider:
public class ColorClass implements ColorInterface {
String color;
ColorClass(String color) {
this.color = color;
}
public String getMeColor(){
return color;
}
public static Provider implements Provider<ColorClass> {
String color;
public Provider(String color) {
this.color = color;
}
public ColorClass get() {
return new ColorClass(color);
}
}
}
and then in your module:
public class ColorModule extends AbstractModule {
#Override
protected void configure() {
bind(ColorInterface.class).annotatedWith(Names.named("BLUE"))
.toProvider(new ColorClass.Provider("Blue"));
bind(ColorInterface.class).annotatedWith(Names.named("RED"))
.toProvider(new ColorClass.Provider("Red"));
bind(ColorInterface.class).annotatedWith(Names.named("ORANGE"))
.toProvider(new ColorClass.Provider("Orange"));
}
}
Obviously, the Provider doesn't need to be a static inner class like I did there, just something in the same package.
In case this exact problem isn't really your problem and you really do need #Named("color") String to be differently injected (say, you've actually got some really deep nested structure pulled together with guice and need a different binding deep in the hierarchy, and can't easily refactor that into a constructor parameter), then you'll need to use private modules.
However, that technique is vast overkill for the case you presented, so I'm hesitant to dive into it here. It's really a rather advanced topic you shouldn't try to tackle unless you really need to solve the problem it solves. (The problem is sometimes referred to as the "Robot Arms" problem)
I have the following classes -
public abstract class BusinessObject { }
public abstract class Form: BusinessObject { }
public abstract class BillableForm: Form { }
public class MembershipForm: BillableForm { }
public abstract class Dto<T>: where T: BusinessObject { }
public abstract class InboxDto<T>: Dto<T> where T: Form { }
public class MembershipFormDto: InboxDto<MembershipForm> { }
And I have the following views -
membershipform.cshtml:
#model AdminSite.Models.MembershipFormDto
#{
Layout = "~/Views/Inbox/Shared/_LayoutForm.cshtml"
}
_LayoutForm.cshtml:
#model InboxDto<Form>
When I land on the membershipform.cshtml page, I get the following exception stating:
The model item passed into the dictionary is of type 'AdminSite.Models.MembershipFormDto', but this dictionary requires a model item of type 'AdminSite.Infrastructure.Models.InboxDto`1[BusinessLogic.Inbox.Form]'.
From everything I can tell, MembershipFormDto IS-A InboxDto of type MembershipForm, where MembershipForm IS-A Form. What gives?
This turned out to be an issue of covariance.
I added the following interface -
public interface IInboxDto<out T>
and modified the InboxDto class to implement that interface -
public abstract class InboxDto<T>: Dto<T>, IInboxDto<T> where T: Form { }
In short, covariance is going from a more defined type to a less defined type; specifically referencing a more defined object with a less defined reference. The reason the compiler complains is it's preventing a scenario like this:
List<String> instanciatedList = new List<String>;
List<Object> referenceList = instanciatedList;
referenceList.add(DateTime);
The final line makes sense, a DateTime IS-A Object. We've said referenceList is a List of Object. However it's instanciated as a List of String. A List of Object is more permissive than a List of String. Suddenly our guarantees from new List<String> are being ignored.
However the out and in keywords for Interface definitions tells the compiler to relax, we know what we're doing and understand what we're getting ourselves into.
More information.
I have a command class that needs to have 2 constructors. However,
using structuremap it seems that I can only specify one constructor to
be used. I have solved the problem for now by subtyping the specific
command class, which each implementation implementing it's own
interface and constructor. Like the code below shows. The
ISelectCommand implements two separate interfaces for the
string constructor and the int constructor, just for the sake of
registering the two subtypes using structuremap.
However, I consider this a hack and I just wonder why is it not
possible for structuremap to resolve the constructor signature by the
type passed in as parameter for the constructor? Then I could register
the SelectProductCommand as an ISelectCommand and
instantiate it like:
ObjectFactury.With(10).Use>();
orObjectFactury.With("testproduct").Use>();
public class SelectProductCommand : ISelectCommand<IProduct>,
ICommand, IExecutable
{
private readonly Func<Product, Boolean> _selector;
private IEnumerable<IProduct> _resultList;
public SelectProductCommand(Func<Product, Boolean> selector)
{
_selector = selector;
}
public IEnumerable<IProduct> Result
{
get { return _resultList; }
}
public void Execute(GenFormDataContext context)
{
_resultList = GetProductRepository().Fetch(context,
_selector);
}
private Repository<IProduct, Product> GetProductRepository()
{
return ObjectFactory.GetInstance<Repository<IProduct,
Product>>();
}
}
public class SelectProductIntCommand: SelectProductCommand
{
public SelectProductIntCommand(Int32 id): base(x =>
x.ProductId == id) {}
}
public class SelectProductStringCommand: SelectProductCommand
{
public SelectProductStringCommand(String name): base(x =>
x.ProductName.Contains(name)) {}
}
P.s. I know how to tell structuremap what constructor map to use, but my again my question is if there is a way to have structuremap select the right constructor based on the parameter passed to the constructor (i.e. using regular method overloading).
The short answer is this post by the creator of Structuremap.
The long answer is regarding the structure you have in that piece of code. In my view, a command is by definition a "class" that does something to an "entity", i.e it modifies the class somehow. Think CreateNewProductCommand.
Here you are using commands for querying, if I'm not mistaken. You also have a bit of a separation of concern issue floating around here. The command posted defines what to do and how to do it, which is to much and you get that kind of Service location you're using in
private Repository<IProduct, Product> GetProductRepository()
{
return ObjectFactory.GetInstance<Repository<IProduct, Product>>();
}
The way I'd structure commands is to use CreateProductCommand as a data contract, i.e it only contains data such as product information.
Then you have a CreateProductCommandHandler which implements IHandles<CreateProductCommand> with a single method Handle or Execute. That way you get better separation of concern and testability.
As for the querying part, just use your repositores directly in your controller/presenter, alternatively use the Query Object pattern
I think I solved the problem using a small utility class. This class gets the concrete type from ObjectFactory and uses this type to construct the instance according to the parameters past into the factory method. Now on the 'client' side I use ObjectFactory to create an instance of CommandFactory. The implementation of CommandFactory is in another solution and thus the 'client solution' remains independent of the 'server' solution.
public class CommandFactory
{
public ICommand Create<T>()
{
return Create<T>(new object[] {});
}
public ICommand Create<T>(object arg1)
{
return Create<T>(new[] {arg1});
}
public ICommand Create<T>(object arg1, object arg2)
{
return Create<T>(new[] {arg1, arg2});
}
public ICommand Create<T>(object arg1, object arg2, object arg3)
{
return Create<T>(new[] {arg1, arg2, arg3});
}
public ICommand Create<T>(object[] arguments)
{
return (ICommand)Activator.CreateInstance(GetRegisteredType<T>(), arguments);
}
public static Type GetRegisteredType<T>()
{
return ObjectFactory.Model.DefaultTypeFor(typeof (T));
}
}
I'm trying to do some attribute-based interception using structuremap but I'm struggling to tie up the last loose ends.
I have a custom Registry that scans my assemblies and in this Registry I have defined the following ITypeInterceptor whose purpose it is to match types decorated with the given attribute and then apply the interceptor if matched. The class is defined as such:
public class AttributeMatchTypeInterceptor<TAttribute, TInterceptor>
: TypeInterceptor
where TAttribute : Attribute
where TInterceptor : IInterceptor
{
private readonly ProxyGenerator m_proxyGeneration = new ProxyGenerator();
public object Process(object target, IContext context)
{
return m_proxyGeneration.CreateInterfaceProxyWithTarget(target, ObjectFactory.GetInstance<TInterceptor>());
}
public bool MatchesType(Type type)
{
return type.GetCustomAttributes(typeof (TAttribute), true).Length > 0;
}
}
//Usage
[Transactional]
public class OrderProcessor : IOrderProcessor{
}
...
public class MyRegistry : Registry{
public MyRegistry()
{
RegisterInterceptor(
new AttributeMatchTypeInterceptor<TransactionalAttribute, TransactionInterceptor>());
...
}
}
I'm using DynamicProxy from the Castle.Core to create the interceptors, but my problem is that the object returned from the CreateInterfaceProxyWithTarget(...) call does not implement the interface that triggered the creation of the target instance in structuremap (i.e IOrderProcessor in example above). I was hoping that the IContext parameter would reveal this interface, but I can only seem to get a hold of the concrete type (i.e. OrderProcessor in example above).
I'm looking for guidance on how to have this scenario work, either by calling the ProxyGenerator to return an instance that implements all interfaces as the target instance, by obtaining the requested interface from structuremap or through some other mechanism.
I actually got something working with a slight caveat so I'll just post this as the answer. The trick was to obtain the interface and pass that into the CreateInterfaceProxyWithTarget. My only problem was that I could not find a way to query the IContext about which interface it was currently resolving so I ended up just looking up the first interface on the target which worked for me. See code below
public class AttributeMatchTypeInterceptor<TAttribute, TInterceptor> :
TypeInterceptor
where TAttribute : Attribute
where TInterceptor : IInterceptor
{
private readonly ProxyGenerator m_proxyGeneration = new ProxyGenerator();
public object Process(object target, IContext context)
{
//NOTE: can't query IContext for actual interface
Type interfaceType = target.GetType().GetInterfaces().First();
return m_proxyGeneration.CreateInterfaceProxyWithTarget(
interfaceType,
target,
ObjectFactory.GetInstance<TInterceptor>());
}
public bool MatchesType(Type type)
{
return type.GetCustomAttributes(typeof (TAttribute), true).Length > 0;
}
}
Hope this helps someone