Microsoft Dynamics AX (Archived)

Inheritance/Method Access Control

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Posted on by Community Member

Hello all,

I have an easy question around method access control I wanted to ask to make sure I'm understanding the concept.

Here would be the scenario.

A Parent Class is created and there is a Parent method in that class.

several child classes will inherit, using extends, from the parent class to use the Parent method.

To ensure the Parent method is available to any Child Class I would set the method modifier in the Parent Method to Protected.

This will allow the Child Class to see the Parent Method.

Alternatively if I set the Parent method to the default Private modifier, the Parent method would not be seen from the child class.

Finally if I set the Parent Method to the Public modifier the Parent method becomes available to any other class which ultimately can lead to bad coding practices and makes things more difficult for debugging.

Is that correct?

Please let me know if it isn't or feel free to add additional comments.

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Vilmos Kintera 46,149 on at

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Hi

Please check the documentation on MSDN: msdn.microsoft.com/.../aa676482.aspx

In AX you typically use public and private keywords for customizations, unless you are writing new framework classes that you intentionally want to be extensible by other partners/customers and using those protected methods within the framework itself.

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Community Member on at

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Vilmos, Thanks for your reply.

From a best practice perspective you would never recommend using the Protected access modifier?

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Martin Dráb 237,801 Most Valuable Professional on at

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Protected methods are widely used. You use them every time when you want some methods to be used by child classes, but not by classes outside the inheritance hierarchy.

Object-oriented development isn't limited to frameworks extended by other companies.

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Vilmos Kintera 46,149 on at

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Take a look at the standard FormLetter class, which is a framework.

There, they are declaring a method like this:

abstract protected PrintMgmtNodeType printMgmtNodeType() { }

There is only an internal call for that in the class in checkClientOutputPrintManagement, thus that is why it is not publicly exposed.

On the class if you see Right click > Add-ins > Type hierarchy browser, you would see how it is being extended by ProjFormLetter class, which does have the method overriden:

protected PrintMgmtNodeType printMgmtNodeType() { return PrintMgmtNodeType::Project; }

If you have no need to explicitly define method abstracts and extend the method by a child class, you are perfectly fine with private/public declarations. Otherwise you need to use the protected keyword.

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