Method API

Method Application Programming Interface

This section describes the C functions and macros that methods use to interface with the Ctalk run time libraries and with each other.

At this point, the method API is still developing, and relies heavily on C library functions.

This example shows method + of class Integer, which adds two Integer objects, creates an object for the result, and returns the result.

Integer instanceMethod + add (int i) {

  OBJECT *op1, *op2;

  op1 = self value;
  op2 = i value;

  methodReturnInteger(atoi(op1->__o_value) + atoi(op2->__o_value))
}

The keyword self refers to the receiver of the method. See Self and super.

The variables op1 and op2 are the value instance variables of the receiver and the argument. Ctalk has a method, value (class Object), which returns the value instance variable, but you can also refer to instance variables by sending an instance variable’s name as a message to an object.

Internally, the receiver, arguments, and return value of a method are all ‘OBJECT *’. When you use C functions with objects, you use the members of an OBJECT type, a struct. (See OBJECT typedef.) If you declare an object as a C OBJECT *, then the method uses it like any other C struct *.

All methods return an ‘OBJECT *’ as the result. The macro methodReturnInteger defines the object that the method returns. See Return values.

The add method is in classes/Integer. The file include/object.h contains the declaration of the ‘OBJECT’ type.