Constructor Function in Delphi - ablealias/Delphi GitHub Wiki

A Constructor is a special method that creates and initializes instance objects. A class can have more than one constructor. When creating an object you should call a Constructor method of the class. The name of the Constructor is normally Create, but not restricted to this. An object may be constructed with or without arguments. Constructor methods you can Override or Overload. See the TObject class Constructor and Destructor implementation part below, no codes in between the begin and end clause.

constructor TObject.Create;
begin 
end;

destructor TObject.Destroy;
begin
end;

To call the parent class Constructor you should specify the Inherited key word as the first statement in your Constructor implementation part. You can call Constructor using an Object reference or a Class reference. Delphi passes an additional, hidden parameter to indicate how it was called. If you call a constructor using a class reference, Delphi calls the class’s NewInstance method to allocate a new instance of the class. After calling NewInstance, the Constructor continues and initializes the object. The constructor automatically sets up a try-except block, and if any exception occurs in the Constructor, Delphi calls the Destructor. See the Constructor calling using class reference,

var
Account: TSavingsAccount;
begin
Account.Create; // wrong {Object reference}
Account := TSavingsAccount.Create; // right {Class reference}

When you call a Constructor with an object reference, Delphi does not set up the try-except block and does not call NewInstance. Instead, it calls the constructor the same way it calls any ordinary method.