Procedures with a long parameter list are difficult to use because maintainers must figure out the role of each parameter and keep track of their
position.
Sub SetCoordinates(x1 As Integer, y1 As Integer, z1 As Integer, x2 As Integer, y2 As Integer, z2 As Integer) ' Noncompliant
' ...
End Sub
The solution can be to:
- Split the procedure into smaller ones
' Each function does a part of what the original setCoordinates function was doing, so confusion risks are lower
Sub SetOrigin(x As Integer, y As Integer, z As Integer)
' ...
End Sub
Sub SetSize(width As Integer, height As Integer, depth As Integer)
' ...
End Sub
- Find a better data structure for the parameters that group data in a way that makes sense for the specific application domain
Class Point ' In geometry, Point is a logical structure to group data
Public x As Integer
Public y As Integer
Public z As Integer
End Class
Sub SetCoordinates(p1 As Point, p2 As Point)
' ...
End Sub
This rule raises an issue when a procedure has more parameters than the provided threshold.
Exceptions
The rule does not count the parameters intended for a base class constructor.
With a maximum number of 4 parameters:
Class BaseClass
Sub New(Param1 As Integer)
' ...
End Sub
End Class
Class DerivedClass
Inherits BaseClass
Public Sub New(Param1 As Integer, Param2 As Integer, Param3 As Integer, Param4 As Integer, Param5 As Long)
' Compliant by exception: Param1 is used in the base class constructor, so it does not count in the sum of the parameter list.
MyBase.New(Param1)
' ...
End Sub
End Class
