Constructors [AX 2012]

Updated: November 30, 2011

Applies To: Microsoft Dynamics AX 2012 R3, Microsoft Dynamics AX 2012 R2, Microsoft Dynamics AX 2012 Feature Pack, Microsoft Dynamics AX 2012

To create an instance of a class (an object), you have to instantiate it. The default constructor is the new method:

// Declares a variable to refer to a Point object

Point myPoint;

;

// Allocates an instance of a Point object

myPoint = new Point();

It is a best practice to make the new method protected, and instead, use a static construct method, or static new method as the public constructor for the class. If no initialization is required, use a static construct method, otherwise use a static new method. For more information, see Best Practices for Constructors.

A class constructor can instantiate other objects, in addition to creating an instance of the class. The following code illustrates one such situation by declaring a Rectangle class that uses two Point objects to define its bounds.

class Rectangle
{
    Point lowerLeft;
    Point upperRight;
}
 
new(real _topLeftX, real _topLeftY, real _bottomRightX, real _bottomRightY)
{
    lowerLeft  = new Point(_topLeftX, _topLeftY);
    upperRight = new Point(_bottomRightX, _bottomRightY);
}

X++ does not allow you to access the variables of an object by referring to the names of the variables, qualified with the name of the object:

myPoint.x = 10.0; //Not possible

myPoint.y = 25.7; //Not possible

The only way to access the member variables in a class is through accessor methods. For information about accessor methods, see Accessor Methods.


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