Method
Operator_Lookup
Operator
Description
Allows the overloading of a class's lookup operator.
Notes
Use Operator_Lookup to define a function that will be called if the called item cannot otherwise be found in the class.
Operator_Lookup overloads a class's lookup operator. The method's first parameter must be a String which will receive the name of the desired member. The method can have any combination of other parameters and can have any return type. The Operator_Lookup operator is called whenever you use the object.member syntax to look up a member of an object and the compiler can't find anything named "bar". Before it returns an Undefined Identifier error, the compiler will try to call a lookup operator and pass "bar" as the first parameter. Overloading works for the lookup operator just as it does for any other method.
Warning
If you implement Operator_Lookup on a class, you will no longer get compilation errors if you, for example, inadvertently misspell a property name. Instead, the Operator_Lookup method is called at runtime and is passed the name of your incorrectly spelled property.
Sample code
Gets values entered as dot notation from a Dictionary and returns the value:
' Gets values entered as dot notation from a dictionary
' MyClass.AnyName returns what is in
' ValueDict.Value("AnyName")
Function Operator_Lookup(name As String) As String
If ValueDict.HasKey(name) Then
Return ValueDict.Value(name)
Else
Return ""
End If
End Function
This code defines "SquareLength" in the Vector class (see Operator Add), a class with two integer properties, x and y.
Function Operator_Lookup(Name As String) As Double
If Name = "SquareLength" Then Return Self.x^2 + Self.y^2
End Function
When you write:
Var myDouble As Double
myDouble = myVector.SquareLength
it will return the result of the calculation. However, you can also write:
myDouble = myVector.UndefinedFunction ' does not exist