I'm in the process of writing a heap of tests around some custom controllers using Moq in VB. Up until now, I've not had to deal with VB Lambda shortcomings since I've only moqed properties or methods.
That is until this morning when I try also running integration tests using Cassini against my code. I had code to add headers using Response.Headers.Add. I did this so I could easily get the headers collection in unit tests using Moq(Of HttpResponseBase) and a SetupGet for Headers->NameValueCollection. Of course, the code chokes in anything other than IIS7 in Integrated Pipeline mode.
So, I changed my code to use Response.AddHeader, which means my unit tests fail. And since I'm in VB, I can' see a sane way to map the call to AddHeader to the Headers collection since Function() needs a return value in VB.
I see a few entries here about Moq and VB, but no one really has the problem of mapping Subs to something else in Moq.
Has anyone tackled this particular situation in VB using Moq?
Ugh. Why do the solutions always become apparently AFTER you post. :-)
This is ugly, but it works.
Subclass HttpResponseBase.
Mock that and set the CallBase to True.
Then override Add/AppendHeader to do Headers.Add. Now you catch any variation people use in code as they all fall into Response.Headers collection. The realy code works regardless of which method you use.
Not as clean as just Moqing Add/Append in C# with callbacks, but it does work.
Dim response As New Mock(Of CustomHttpResponse)
response.SetupGet(Function(r As HttpResponseBase) r.Headers).Returns(New NameValueCollection)
response.CallBase = True
Public Class CustomHttpResponse
Inherits HttpResponseBase
Public Overrides Sub AddHeader(ByVal name As String, ByVal value As String)
Me.Headers.Add(name, value)
End Sub
Public Overrides Sub AppendHeader(ByVal name As String, ByVal value As String)
Me.Headers.Add(name, value)
End Sub
End Class
Related
After reading this piece by Yegor about not using getters and setters, it sounds like something that makes sense to me.
Please note this question is not about whether doing it is better/worst, only if I am implementing it correctly
I was wondering in the following two examples in VBA, if I understand the concept correctly, and if I am applying it correctly.
The standard way would be:
Private userName As String
Public Property Get Name() As String
Name = userName
End Property
Public Property Let Name(rData As String)
userName = rData
End Property
It looks to me his way would be something like this:
Private userName As String
Public Function returnName() As String
returnName = userName
End Function
Public Function giveNewName(newName As String) As String
userName = newName
End Function
From what I understand from the two examples above is that if I wanted to change the format of userName (lets say return it in all-caps), then I can do this with the second method without changing the name of the method that gives the name through - I can just let returnName point to a userNameCaps property. The rest of my code in my program can still stay the same and point to the method userName.
But if I want to do this with the first example, I can make a new property, but then have to change my code everywhere in the program as well to point to the new property... is that correct?
In other words, in the first example the API gets info from a property, and in the second example the API gets info from a method.
Your 2nd snippet is neither idiomatic nor equivalent. That article you link to, is about Java, a language which has no concept whatsoever of object properties - getFoo/setFoo is a mere convention in Java.
In VBA this:
Private userName As String
Public Property Get Name() As String
Name = userName
End Property
Public Property Let Name(rData As String)
userName = rData
End Property
Is ultimately equivalent to this:
Public UserName As String
Not convinced? Add such a public field to a class module, say, Class1. Then add a new class module and add this:
Implements Class1
The compiler will force you to implement a Property Get and a Property Let member, so that the Class1 interface contract can be fulfilled.
So why bother with properties then? Properties are a tool, to help with encapsulation.
Option Explicit
Private Type TSomething
Foo As Long
End Type
Private this As TSomething
Public Property Get Foo() As Long
Foo = this.Foo
End Property
Public Property Let Foo(ByVal value As Long)
If value <= 0 Then Err.Raise 5
this.Foo = value
End Property
Now if you try to assign Foo with a negative value, you'll get a runtime error: the property is encapsulating an internal state that only the class knows and is able to mutate: calling code doesn't see or know about the encapsulated value - all it knows is that Foo is a read/write property. The validation logic in the "setter" ensures the object is in a consistent state at all times.
If you want to break down a property into methods, then you need a Function for the getter, and assignment would be a Sub not a Function. In fact, Rubberduck would tell you that there's a problem with the return value of giveNewName being never assigned: that's a much worse code smell than "OMG you're using properties!".
Functions return a value. Subs/methods do something - in the case of an object/class, that something might imply mutating internal state.
But by avoiding Property Let just because some Java guy said getters & setters are evil, you're just making your VBA API more cluttered than it needs to be - because VBA understands properties, and Java does not. C# and VB.NET do however, so if anything the principles of these languages would be much more readily applicable to VBA than Java's, at least with regards to properties. See Property vs Method.
FWIW public member names in VB would be PascalCase by convention. camelCase public member names are a Java thing. Notice how everything in the standard libraries starts with a Capital first letter?
It seems to me that you've just given the property accessors new names. They are functionally identical.
I think the idea of not using getters/setters implies that you don't try to externally modify an object's state - because if you do, the object is not much more than a user-defined type, a simple collection of data. Objects/Classes should be defined by their behavior. The data they contain should only be there to enable/support that behavior.
That means you don't tell the object how it has to be or what data you want it to hold. You tell it what you want it to do or what is happening to it. The object itself then decides how to modify its state.
To me it seems your example class is a little too simple to work as an example. It's not clear what the intended purpose is: Currently you'd probably better off just using a variable UserName instead.
Have a look at this answer to a related question - I think it provides a good example.
Regarding your edit:
From what I understand from the two examples above is that if I wanted
to change the format of userName (lets say return it in all-caps),
then I can do this with the second method without changing the name of
the method that gives the name through - I can just let returnName
point to a userNameCaps property. The rest of my code in my program
can still stay the same and point to the method iserName.
But if I want to do this with the first example, I can make a new
property, but then have to change my code everywhere in the program as
well to point to the new property... is that correct?
Actually, what you're describing here, is possible in both approaches. You can have a property
Public Property Get Name() As String
' possibly more code here...
Name = UCase(UserName)
End Property
or an equivalent function
Public Function Name() As String
' possibly more code here...
Name = UCase(UserName)
End Function
As long as you only change the property/function body, no external code needs to be adapted. Keep the property's/function's signature (the first line, including the Public statement, its name, its type and the order and type of its parameters) unchanged and you should not need to change anything outside the class to accommodate.
The Java article is making some sort of philosophic design stance that is not limited to Java: The general advise is to severely limit any details on how a class is implemented to avoid making one's code harder to maintain. Putting such advice into VBA terms isn't irrelevant.
Microsoft popularized the idea of a Property that is in fact a method (or two) which masquerade as a field (i.e. any garden-variety variable). It is a neat-and-tidy way to package up a getter and setter together. Beyond that, really, behind the scenes it's still just a set of functions or subroutines that perform as accessors for your class.
Understand that VBA does not do classes, but it does do interfaces. That's what a "Class Module" is: An interface to an (anonymous) class. When you say Dim o As New MyClassModule, VBA calls some factory function which returns an instance of the class that goes with MyClassModule. From that point, o references the interface (which in turn is wired into the instance). As #Mathieu Guindon has demonstrated, Public UserName As String inside a class module really becomes a Property behind the scenes anyway. Why? Because a Class Module is an interface, and an interface is a set of (pointers to) functions and subroutines.
As for the philosophic design stance, the really big idea here is not to make too many promises. If UserName is a String, it must always remain a String. Furthermore, it must always be available - you cannot remove it from future versions of your class! UserName might not be the best example here (afterall, why wouldn't a String cover all needs? for what reason might UserName become superfluous?). But it does happen that what seemed like a good idea at the time the class was being made turns into a big goof. Imagine a Public TwiddlePuff As Integer (or instead getTwiddlePuff() As Integer and setTwiddlePuff(value As Integer)) only to find out (much later on!) that Integer isn't sufficient anymore, maybe it should have been Long. Or maybe a Double. If you try to change TwiddlePuff now, anything compiled back when it was Integer will likely break. So maybe people making new code will be fine, and maybe it's mostly the folks who still need to use some of the old code who are now stuck with a problem.
And what if TwiddlePuff turned out to be a really big design mistake, that it should not have been there in the first place? Well, removing it brings its own set of headaches. If TwiddlePuff was used at all elsewhere, that means some folks may have a big refactoring job on their hands. And that might not be the worst of it - if your code compiles to native binaries especially, that makes for a really big mess, since an interface is about a set of function pointers layed out and ordered in a very specific way.
Too reiterate, do not make too many promises. Think through on what you will share with others. Properties-getters-setters-accessors are okay, but must be used thoughtfully and sparingly. All of that above is important if what you are making is code that you are going to share with others, and others will take it and use it as part of a larger system of code, and it may be that these others intend to share their larger systems of code with yet even more people who will use that in their even larger systems of code.
That right there is probably why hiding implementation details to the greatest extent possible is regarded as fundamental to object oriented programming.
So we recently migrated an application from .NET 1.1 to .NET 4.0.
And with that, there was a bunch of compatibility issues which we had to fix.
One of them is that a block of code is throwing the InvalidOperationException.
Public Function MyFunction(ByVal Params As myParams, ByVal ParamArray someNumber As Integer()) As myData
...
If someNumber.BinarySearch(options, MyEnum.Something) >= 0 Then
...
EndIf
...
EndFunction
Before we migrated to .NET4 this was working correctly in .NET1. Now based on some threads i've been reading, there has been reports about this problem which was fixed in .NET4.5. And that to fix this in my current version, I have to implement the IComparable interface on all elements of the array.
How do I go about to fixing this? I would appreciate any help and pointer. Thanks!
EDIT: Adding the link to the BinarySearch method we are using in the code. https://msdn.microsoft.com/en-us/library/y15ef976.aspx
Add Implements IComparable IComparable Interface to your class definition. 2. Add a method for IComparable.CompareTo to the class. Borrowing from msdn:
Public Class Temperature
Implements IComparable
' The temperature value
Protected temperatureF As Double
Public Overloads Function CompareTo(ByVal obj As Object) As Integer _
Implements IComparable.CompareTo
If obj Is Nothing Then Return 1
Dim otherTemperature As Temperature = TryCast(obj, Temperature)
If otherTemperature IsNot Nothing Then
Return Me.temperatureF.CompareTo(otherTemperature.temperatureF)
Else
Throw New ArgumentException("Object is not a Temperature")
End If
End Function
....
End Class
Of coarse the code in the CompareTo function depends on your class (you didn't provide much to go on). All numeric types (such as Int32 and Double) implement IComparable, as do String, Char, and DateTime. Custom types should also provide their own implementation of IComparable to enable object instances to be ordered or sorted. I believe that might be the situation in your case. I hope this helps.
Try this:
...
Array.Sort(Of Integer)(someNumber) ' only if someNumber is not previously sorted
If Array.BinarySearch(Of Integer)(someNumber, MyEnum.Something) >= 0 Then
...
End If
...
This should work in all .NET frameworks > 2.0.
How do I go about to fixing this?
You are not using it correctly. BinarySearch is a Shared/static method and doesnt show in Intellisense when trying to use it as an instance method:
If you type it in anyway, you get a new compiler warning: Access of shared member ... through an instance ... will not be evaluated. MSDN doesnt have anything for NET 1.1, so I dont know if it changed since then (doubtful). Correct usage:
IndexOf6 = Array.BinarySearch(myIntAry, 6)
Which begs the question, as part of the conversion from NET 1.x to 4.5, why not convert this to List(Of Int32). A quick test shows that the IndexOf() method is 2-3 times faster:
IndexOf6 = intList.IndexOf(6)
The List<T> method is also more 'standalone' since unlike a System.Array, it need not be sorted in order to work.
I'm trying to rebuild some old QBASIC (yeah, you read that right) programs for use on more modern systems (because for some reason kids these days don't like DOS).
I understand the basic principles of classes and objects (I think) but I'm obviously missing something.
I have a number of instruments which are controlled using GPIB, using VISA COM libraries. I can make it work, but the code is very ugly :(
In order to use an instrument, I have the following in my Public Class Main:
Public ioMgr As Ivi.Visa.Interop.ResourceManager
Dim myInstrument As New Ivi.Visa.Interop.FormattedIO488
Dim myInstOpen As Boolean
Then, when I come to initializing the instrument (in the 'Initialize' button click sub), I use:
Try
myInstrument.IO = ioMgr.Open("GPIB0::17")
Catch exOpen As System.Runtime.InteropServices.COMException
myInstOpen = False
End Try
Pretty straightforward stuff; if the instrument can't be opened at address 17 on GPIB0, it throws an exception, which gets caught and sets the 'myInstOpen' flag to false.
Then, I can communicate with the instrument using commands from the Ivi.Visa.Interop.FormattedIO488 interface such as:
myInstrument.IO.ReadSTB()
result = myInstrument.ReadString()
myInstrument.WriteString("GPIB Command Here")
And all of it works.
What I want to do is, create a generic 'Instrument' class, that allows me access to all the functions from the Ivi.Visa.Interop.FormattedIO488 interface, and from the Ivi.Visa.Interop.ResourceManager interface, but also allows me to build my own class.
For instance:
Public Class GPIBInst
Implements Ivi.Visa.Interop.FormattedIO488
Public Address As Integer
Public Sub setAddress(ByVal Addr As Integer)
Address = Addr
End Sub
Public Function getAddress() As Integer
Return Address
End Function
Public Function readIO() As String
Dim Data As String = me.ReadString()
Dim Result As String = mid(Data,2,7)
Return Result
End Function
End Class
This would allow me to use the functions from the interface, but also customize the instruments for other useful things inside the program. For instance, the GPIBInst.Address needs to be used in other places, and the GPIBInst.readIO() can be used instead of just the generic ReadString() so that I can customize the output a little.
BUT when I try to do this, I can't inherit from the interface (because it's an interface) and I can't implement the interface because it says my class needs to implement every single function which the interface provides. I don't want all these functions, and also, I can't work out how to write them all into my class anyway (they have heaps of random stuff in them which I don't understand lol).
If anyone can see where I'm coming from and can offer some advice, I'd really appreciate it =)
An interface is supposed to represent a coherent set of functionality; implementing part of it but not all of it violates the intent of the concept. That being said, it is very common for APIs in object-oriented languages that wrap non-OO systems to just define one massive interface rather than breaking the functionality into logical sub-groups and defining an interface for each group. If that is your circumstance, and you want to implement the interface, you have no choice but to implement every method from the interface (although you can throw a NotImplementException for any method that you don't want to fully implement, as long as that will not prevent your class from functioning properly).
I have been implementing Dependency Injection into an existing Winforms project and it has been going well so far, however I want to generalise the calling of the Forms, specifically the varying quantity of constructor parameters.
My code is as follows:
Public Shared Function GetForm(formObject As BaseObject, _
parameters As Dictionary(Of String, Object)) As Form
Select Case formObject.GetType()
Case GetType(Production.Task)
Return SMKernel.Kernel.Get(Of Forms.Production.Domain.ManageTask) _
(New Parameters.ConstructorArgument() _
{New Parameters.ConstructorArgument("task", _
CType(formObject, Production.RequiredTask))})
End Select
End Function
This works fine, the interface(s) are injected correctly, the constructor parameter "task" is populated and the Form works as expected.
As you can see I have a Dictionary that can contain several parameters which I need to add to the ConstructorArgument part of the Get method. Looking at the IntelliSense, I should be able to pass in an array of ConstructorArgument objects, however no matter what I have tried, it doesn't seem to work for one reason or another.
How do you accomplish this in Ninject if it is at all possible. If this way isn't possible, how can you pass multiple parameters into a Form's constructor via Ninject?
Use the already provided ResolutionExtensions
public static T Get<T>(this IResolutionRoot root, params IParameter[] parameters)
Then combine it with LINQ
Kernel.Get(parameters.Select(kvp => new ConstructorArgument(kvp.Key, kvp.Value)).ToArray())
Provide more details and we might give you are more elegant approach.
I'm (somewhat) new to DI and am trying to understand how/why it's used in the codebase I am maintaining. I have found a series of classes that map data from stored procedure calls to domain objects. For example:
Public Sub New(domainFactory As IDomainFactory)
_domainFactory = domainFactory
End Sub
Protected Overrides Function MapFromRow(row As DataRow) As ISomeDomainObject
Dim domainObject = _domainFactory.CreateSomeDomainObject()
' Populate the object
domainObject.ID = CType(row("id"), Integer)
domainObject.StartDate = CType(row("date"), Date)
domainObject.Active = CType(row("enabled"), Boolean)
Return domainObject
End Function
The IDomainFactory is injected with Spring.Net. It's implementation simply has a series of methods that return new instances of the various domain objects. eg:
Public Function CreateSomeDomainObject() As ISomeDomainObject
Return New SomeDomainObject()
End Function
All of the above code strikes me as worse than useless. It's hard to follow and does nothing of value. Additionally, as far as I can tell it's a misuse of DI as it's not really intended for local variables. Furthermore, we don't need more than one implementation of the domain objects, we don't do any unit testing and if we did we still wouldn't mock the domain objects. As you can see from the above code, any changes to the domain object would be the result of changes to the SP, which would mean the MapFromRow method would have to be edited anyway.
That said, should I rip this nonsense out or is it doing something amazingly awesome and I'm missing it?
The idea behind dependency injection is to make a class (or another piece of code) independent on a specific implementation of an interface. The class outlined above does not know which class implements IDomainFactory. A concrete implementation is injected through its constructor and later used by the method MapFromRow. The domain factory returns an implementation of ISomeDomainObject which is also unknown.
This allows you supplement another implementation of these interfaces without having to change the class shown above. This is very practical for unit tests. Let's assume that you have an interface IDatabase that defines a method GetCustomerByID. It is difficult to test code that uses this method, since it depends on specific customer records in the database. Now you can inject a dummy database class that returns customers generated by code that does not access a physical database. Such a dummy class is often called a mock object.
See Dependency injection on Wikipedia.