Let's say I'm making a task list application, and let's say that there's a Task class and a TaskList class. Now, what would be the best way to add a Task to the TaskList?
new Task(TaskList,"task name")
or
TaskList.addTask("task title")
in the second case, the TaskList would be responsible for instanciating the Task class.
I'd go for the second option.
However, there could be coupled with a third option available that allows you to extend the Task class, that is a method with the following signature
TaskList.Add(Task task);
This way you would instantiate the Task class, set all properties, and then add it to the TaskList object.
Ideally, the TaskList.addTask(string taskName) method you defined, could be a helper method that ends up internally calling the third method, and you could leave that method available if you need to support greater flexibility in setting the Task object properties.
Related
In my Restler index.php let's say I've done this:
$r->addAPIClass('Person');
$r->addAPIClass('Team');
And now I'm inside one of the methods defined in Person, and I have a need to call one of the methods defined in Team. What's the right way to get a handle to the Team API so that I can call one of its methods?
There is nothing special, doing it with Restler.
If it is a static method directly call Team::method(parameter)
Otherwise create an instance either
at constructor if you need it in many methods and store it in a private variable
at the method level
If you are using a database model, it may already provide you with an instance of team as a relationship
I am looking to find out how to use Ninject to get all instances that inherit from a base class that also pass some custom Boolean criteria. This is a continuation of a previous question. This is how I am creating a binging for all classes that inherit from MyAbstractClass.
_kernel.Bind(x => { x
.FromThisAssembly()
.SelectAllClasses()
.InheritedFrom<MyAbstractClass>()
.BindAllBaseClasses()
.Configure(syntax => syntax.InSingletonScope());
});
If I have the syntax correct, this will create a singleton scope binding for all classes that inherit from MyAbstractClass. Next I need to get/construct all the classes.
IEnumerable<MyAbstractClass> items = kernel.GetAll<MyAbstractClass>();
The code above will get/create all classes that inherit from MyAbstractClass.
Now I need to add one more step to this process. Based on “access roles” not all classes that inherit from MyAbstractClass should be created because the current user might not have access to functionality for every derived class. So I tried adding a CanLoad Boolean to each derived class and tried the following.
IEnumerable<MyAbstractClass> items = kernel.GetAll<MyAbstractClass>().Where(x => x.CanLoad == true);
While items did contain only the classes I expected, based on my CanLoad logic, I did see the constructor for each derived class being called because of the kernel.GetAll() method. Also it will have to create the class to call its CanLoad method, so that will not work. I thought about making the CanLoad static too. I also thought about a method that would look similar to the following.
public bool CanLoad<T>() where T : MyAbstractClass {
//return true if the current user has the correct access roles to create class of type T
}
So my question is how can I use the Ninject GetAll() method to get all classes that inherit from MyAbstractClass that also return true for the CanLoad Boolean method? I have been trying to use Ninject and Linq and possibly Reflection but I do not have a solution yet.
Edit:
To elaborate on the “permission logic”, at the very beginning our app calls out to a web service to get a list of LDAP groups/roles which are returned as a simple list of string. Each of the derived classes are actually ViewModels and each ViewModel “needs” a minimum role for its functionality to be usable by the current user. I thought I could tie the Ninject/binding/get logic with some custom “permission logic” and only bind/get classes the current user has access to. The list of VMs become an ItemsSource binding for a docking control (and we are considering using creating an ItemsSource binding for the Ribbon control as well). It’s all research at this point.
Add a When constraint to the binding:
.Configure(syntax => syntax
.When(... check permission here...)
.InSingletonScope());
Since you didn't say anything about the logic how you know whether the user has permission, i can't give you more specific information here. But generally speaking, you should add a 'When' constraint to your binding whenever you want to make sure it cannot and will not be instanciated unless a condition is met.
Say your code receives an instance from an external source, and you had no control over how the instance was created. The instance does not implement INotifyPropertyChanged. Is there an adapter you can pass it to, as in:
var adapter = new ChangeNotifierAdapter( instance );
such that the adapter implements INotifyPropertyChanged and will thereafter raise its PropertyChanged event for all property changes of instance?
If you can guarantee that all changes to the instance will go via your wrapper, then you can use a proxy - either a dynamic one or one generated at design time (nb: if you have to still expose the concrete class rather than an interface it'll have to be a dynamic proxy).
If that's not true (or even if it is, but changes to one property affect the value of another) then the only way to achieve this is via polling. The wrapper has to periodically poll all the properties of the object, determine which have changed and raise events accordingly. This is messy, and can be a serious battery drain on mobile devices.
Both suck of course. Mapping to an object that does implement it is generally a better solution.
Long post - sorry....
I'm doing input validation for a WCF service and using StructureMap IoC to instantiate the appropriate validation objects.
I have 2 different validation groups:
Per object validation: means that one input parameter, will be resolve by the Ioc (e.g. Ioc.ResolveAll<IValidatorObject<InputParameter1>, .... <InputParameter2>... etc). If any rules are found, the validate method is invoked.
Per context validation: mean that validation rules are invoked, based on the current context (explicit roles). A context could be 'deposit money' or 'open bank account'. Context validation are usually dependent on 2 or more of the input parameters and is the key difference between object and context validation.
The input validation is performed in the BeforeCall event call in the IParameterInspector (provider/server side!). With this event I get a string containing the operation name (aka. the context) and an object[] with the input parameters.
The problem is that there's multiple validation rules for a single context and the only way I have figured out to register the context in the Ioc, is by using named intances. However I can only register 1 named instance pr. interface. And the interface is not uniquely identifiable by its signature. E.g.
Context rule for 'create account': IValidatorContext<User, Account>
Context rule for 'deposit money': IValidatorContext<User, Account>
So my question is, whether it is possible to register the context in StructureMap in any other way than named instances - or maybe a way to group named instances.
An alternative route, is to implement explicit interfaces for each context, so that the DepositMoney service method might look like this:
public Response Deposit(IDepositMoney inputArguements)
where IDepositMoney contains the input parameters.
So am I way off here, or can I somehow register a context in StructureMap? Or should I just go ahead and use explicit interface instead (3rd option?)
Thanks in advance
Ended up wrapping each set of input parameters in a context and used the context to register in StructureMap. Works like a charm!
The whole idea of named instances is that the name points to a single instance, so you won't be able to use that feature to do what you are trying to achieve. I would use explicit interfaces, since this will allow you to auto wire more things and have less calls to your container.
I am interested in the best practice of the following scenario. I have a CustomAction method that hits a web service and returns some information that I use to populate a combo box. Later in the install process in another CustomAction method, I need to access some of the meta data returned from that first web service call.
In the first method, I create a List that is a public static member of my CustomAction class. In my second method when I access the list its empty.
My thoughts were to serialize it using xaml serialization into a session variable then deserialize it in my second method.
Am I way off here? Is there a better way?
I will assume that your second custom action is making configuration changes to the machine and running in the execute sequence as deferred with no impersonation. This means it can only access the CustomActionData property.
This means your first custom action will have to serialize the CustomActionData property for the second one to deserialize. Now the CustomActionData is a Key:Value collection and what you do with it ( including have a Key with a Value that is yet another serialized datatype ) is completely up to you.
Be sure to read the DTF documentation to understand how to use the CustomActionData type and members off the Session class to your advantage.