What does putting an exclamation point (!
) in front of an object reference variable do in Visual Basic 6.0?
For example, I see the following in code:
!RelativePath.Value = mstrRelativePath
What does the !
mean?
If you have ever noticed a double exclamation mark (!!) in someone's JavaScript code you may be curious what it's for and what it does. It's really simple: it's short way to cast a variable to be a boolean (true or false) value.
It's a negation or "not" operator. In practice ! number means "true if number == 0, false otherwise." Google "unary operators" to learn more.
The exclamation mark (non-null assertion) operator removes null and undefined from the type of an expression. It is used when we we know that a variable that TypeScript thinks could be null or undefined actually isn't. index.ts. Copied!
In Javascript, the exclamation mark (“!”) symbol, called a “bang,” is the logical “not” operator. Placed in front of a boolean value it will reverse the value, returning the opposite.
It is almost certainly a statement inside a With block:
With blah !RelativePath.Value = mstrRelativePath End With
which is syntax sugar for
blah("RelativePath").Value = mstrRelativePath
which is syntax sugar for
blah.DefaultProperty("RelativePath").Value = mstrRelativePath
where "DefaultProperty" is a property with dispid zero that's indexed by a string. Like the Fields property of an ADO Recordset object.
Somewhat inevitable with sugar is that it produces tooth decay. This is the reason you have to use the Set keyword in VB6 and VBA. Because without it the compiler doesn't know whether you meant to copy the object reference or the object's default property value. Eliminated in vb.net.
The exclamation point is acting as a member access operator it seems...
Member Access Operators
To access a member of a type, you use the dot (.) or exclamation point (!) operator
I take that back. It is this:
Exclamation Point (!) Operator Use the ! operator only on a class or interface as a dictionary access operator. The class or interface must have a default property that accepts a single String argument. The identifier immediately following the ! operator becomes the string argument to the default property.
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