问题
This is a simple question I hope. I learned about IIf today and want to implement it in some cases to save a few lines.
IIF(isnumeric(inputs), resume next, call notnum)
This is in red meaning there is a syntax error, how fix this? I have scanned MSDN article on this so I am not being lazy here.
回答1:
That's not how the IIf function works.
It's a function, not a statement: you use its return value like you would with any other function - using it for control flow is a bad idea.
At a glance, IIf works a little bit like the ternary operator does in other languages:
string result = (foo == 0 ? "Zero" : "NonZero");
Condition, value if true, value if false, and both possible values are of the same type.
It's for turning this:
If foo = 0
Debug.Print "Zero"
Else
Debug.Print "NonZero"
End If
Into this:
Debug.Print IIf(foo = 0, "Zero", "NonZero")
Be careful though, IIf evaluates both the true and the false parts, so you will not want to have side-effects there. For example, calling the below Foo procedure:
Public Sub Foo()
Debug.Print IIf(IsNumeric(42), A, B)
End Sub
Private Function A() As String
Debug.Print "in A"
A = "A"
End Function
Private Function B() As String
Debug.Print "in B"
B = "B"
End Function
Results in this output:
in A
in B
A
That's why using IIf for control flow isn't ideal. But when the true result and false result arguments are constant expressions, if used judiciously, it can help improve your code's readability by turning If...Else...End If blocks into a simple function call.
Like all good things, best not abuse it.
回答2:
You cannot use iif like this.
Here is a possible way to solve this:
if isnumeric(input) then
do something ...
else
call notnum
end if
回答3:
IIf returns a value. As Mat's Mug stated, you can use it, to hand data into another method or function, but you can't call a procedure or function, which has no return value. IsNumeric() for the conditional is okay, though.
来源：https://stackoverflow.com/questions/34211344/syntax-error-using-iif