Class instantiation

Classes must be created using their constructor. Remember that a class is a pointer to an object, so when you declare a variable of some class, the compiler just allocates a pointer, not the entire object. The constructor of a class returns a pointer to an initialized instance of the object.

So, to initialize an instance of some class, you would do the following :

You cannot use the extended syntax of new and dispose to instantiate and destroy class instances. That construct is reserved for use with objects only.

Calling the constructor will provoke a call to getmem, to allocate enough space to hold the class instance data. After that, the constuctor's code is executed. The constructor has a pointer to it's data, in self.

Remark :

• The {$PackRecords } directive also affects classes. i.e. the alignment in memory of the different fields depends on the value of the {$PackRecords } directive.
• Just as for objects and records, you can declare a packed class. This has the same effect as on an object, or record, namely that the elements are aligned on 1-byte boundaries. i.e. as close as possible.
• SizeOf(class) will return 4, since a class is but a pointer to an object. To get the size of the class instance data, use the TObject.InstanceSize method.