CODEWITHSUNDEEP
.netvb.nettheory
wavedrop
wavedrop

Reputation: 530

Methods for Checking Business Rules

I hope this is in the right place. I was having a discussion with a colleague about a method used to check business rules. In general there are two conditions:

  1. "If one fails the whole thing fails"

Example 1: "If one fails the whole thing fails"

I have used the following technique for condition 1 in several cases. Essentially if one of those conditions is false then the whole thing fails

Dim blnTemp As Boolean = True

If Fail=False Then blnTemp = blnTemp AndAlso False

    {code code code}

If Fail=True Then blnTemp = blnTemp AndAlso False

    {code code code}

If Fail=False Then blnTemp = blnTemp AndAlso False

    {code code code}

If Fail=False Then blnTemp = blnTemp AndAlso False

    {yup, code code code}

If True Then
    Execute("Execute Global Thermal Nuclear War")
End If

So I am wondering if anyone has any other techniques that they have used for rule checks?

Upvotes: 0

Views: 201

Answers (3)

Alex
Alex

Reputation: 8116

I usually try to go with the "Fail fast, fail hard" idea. Basically leaving the method as soon as the first required condition is not met. 

Public Function NuclearWar() as Boolean
   If not is Foo() then return False
   If (FooList is Nothing AndAlso FooList.Count = 0) then return False
   (...) etc.

   return True
End Function

For me, its clearer to read instead of going down each check and return the result at the end. If the "whole thing" fails if one of the conditions is false, that early jump off comes in quite handy - as long as you don't need to examine the result of the other checks which are left out because of the return.

@Comment

but if your conditions are separated by other work that needs to be done then one function call would not be sufficient. Or would it? What would you do

Well, readability and clean code (Which includes easy following of the control flow) is one of the things I care about. So I'd most likely group conditions which are related together. If the conditions are separated by other work, I'd abstract the conditions in a class, say LaunchConditions.

Public Class LaunchCondition
    Public Property IsLaunch As Boolean
    ' Add other properties you'd like to check
End Class
Public Class LaunchConditions
    Private _launchConditions = New List(Of LaunchCondition)
    Public ReadOnly Property CanLaunch As Boolean
        Get
            Return CheckConditions()
        End Get
    End Property
    Public Sub AddCondition(ByVal condition As LaunchCondition)
        ' Add condition
    End Sub
    Public Sub RemoveCondition(ByVal condition As LaunchCondition)
        ' Add condition
    End Sub
    Private Function CheckConditions() As Boolean
        ' Your check logic
        Return _launchConditions.Any(Function(x As LaunchCondition) Not x.IsLaunch)
    End Function
End Class

Hope this gives you some ideas :)

Upvotes: 3

fjdumont
fjdumont

Reputation: 1537

For me, Linq does the job concisely and easily readable.

Dim nuclearWarConditions As IEnumerable(Of Boolean) = New Boolean() { _
    True, _
    True, _
    True, _
    False, _
    True
}

If nuclearWarConditions.All(Function(condition) condition = True) Then
    Console.WriteLine("Execute Global Thermal Nuclear War")
End If

Analogically, you may use

If nuclearWarConditions.Any(Function(condition) condition = False) Then
    Console.Error.WriteLine("Cancelled Global Thermal Nuclear War")
End If

to reduce nesting.

Edit: Sorry in case i messed up the VB syntax. I'm not a native speaker :)

Upvotes: 2

Guy Starbuck
Guy Starbuck

Reputation: 21873

I'm not sure what the difference is between your two scenarios - isn't "all must be true" the same as "if one fails the whole thing fails"?

In any case, assuming your processing is already done, I wouldn't mess with all the If/Then statements, but go with something cleaner:

if (conditional1 && conditional2 && conditional3...)
    {return true}
else
    {return false}

Upvotes: 0

Related Questions