Best Practices for new and static new... Methods

  • Article

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

The new method is the default constructor for a class. The new method should be protected. Warning icon Do not use it to instantiate the class. Use a construct or a static new… method instead.

It is recommended that you do not have parameters on the new method—use static new… methods instead.

X++ does not support method-name overloading. You must create your own individually named static new… methods with different parameter profiles. This enables you to construct a class in more than one way. Similarly, instead of creating default parameters in a new method, create a different static new… method for each possible parameter profile.

If you have created the new method on a subclass, call super() to carry out any necessary initialization that might be implemented in the superclass. The call to super() should be the first statement in the method.

static new… Methods

Create one or more static new… methods to instantiate your class.

These new methods have the following characteristics:

  • Are public

  • Are static

  • Have a name prefixed with "new"

  • Are named according to the parameter(s) they take, or logically

  • Usually take only nondefault parameters

  • Always return a valid object of the class's type (instantiated as well as initialized), or throw an error

  • Use a construct method to create an instance of the class

  • Use accessor methods to set the class variables

The static new… methods have a body that contains the following structure.

    MyClass myClass;
    ;
    
    // The construct method is used to create an instance of the class.
    myClass = MyClass::construct(...); 
      
    // Use accessor methods to set the class variables.
    myClass.parmOneValue(...);
    myClass.parmAnotherValue(...);
      
    if (!myClass.init())
    {
        throw error("Label text explaining why object was not created");
    }
    return myClass;

See also

Best Practices for Constructors

Best Practices for init Methods

Best Practices for Accessor Methods

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