Self

The self keyword refers to the current instance of the class that a block of code belongs to. It provides access to the members of the class (although by default they are in scope without the need for a self, and also makes the current instance available, for exa ple to be passed or assigned to other places.

type
  Foo = public class
  private
    property Value: String;
    
  public
  
    method Test;
    begin
      var x := Value;        // members can be access directly...
      var u := self.Value;   // ... but also via `self`;
      
      var f: Foo := self;    // `self` represents the instance as a whole.
    end;

  end;

As discussed in Member Access Expressions, self can be helpful to avoid ambiguity, or access class members that are "hidden" from by another identifier of the same name. It can also provide clarity and code improve readability, in places where it might not be obvious which identifiers refer to type members, and which don't:

method UpdateValue(Value: String);
begin
  self.Value := Value; // the paramer hides the property
end;

Self in Static Members

In static members (defined with the static modifier or the class method/class property, class var or class event prefix), self refers to the (platform-specific) meta-class that describes the current type. This can be assumed to be unique for each type, and distinct for separate types, and allows for polymorphism (i.e. in descendant class, self will refer to the descendant meta-class:

self inside a static member is identical to typeOf(self) in an instance method.

See Also