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I had to delve into some VB6 code recently and I saw this pattern all over the place:
dim o as obj
set o = new obj
Why not this?
dim o as new obj
I remember from 15 years ago that there was a good reason for this, but I can't remember what it was now. Anyone remember? Is the reason still valid?
538
Declaration: The code set in bold are all variable declarations that associate a variable name with an object type. Instantiation: The new keyword is a Java operator that creates the object. Initialization: The new operator is followed by a call to a constructor, which initializes the new object.
An instance of an object can be declared by giving it a unique name that can be used in a program. This process is known as instantiation. A class can also be instantiated to create an object, a concrete instance of the class.
Instantiation allocates the initial memory for the object and returns a reference. An instance is required by non-static methods as they may operate on the non-static fields created by the constructor.
Instantiate (a verb) and instantiation (the noun) in computer science refer to the creation of an object (or an “instance” of a given class) in an object-oriented programming (OOP) language. Referencing a class declaration, an instantiated object is named and created, in memory or on disk.
There may be other reasons but in VB6 using the New keyword when you Dim an object can cause unexpected results because VB will instantiate the object whenever it is referenced.
Dim objMyObject as New SomeObject
Set objMyObject = Nothing ' the object is nothing
If objMyObject Is Nothing Then ' referencing the object instantiates again
MsgBox "My object is destroyed" ' what you would probably expect
Else
MsgBox "My object still exists"
End If
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