Home > Articles > Programming > C#

C# Design Patterns: Adapter

The great adaptability of C# is one of its assets, but coding for a wide variety of platforms can be overwhelming. This chapter by Steven John Metsker will help you adapt your code to different situations with ease.
This chapter is from the book

This chapter is from the book

An object is a client if it needs to call your code. In some cases, client code will be written after your code exists and the developer can mold the client to use the interfaces of the objects that you provide. In other cases, clients may be developed independently of your code. For example, a rocket simulation program might be designed to use rocket information that you supply, but such a simulation will have its own definition of how a rocket should behave. In such circumstances, you may find that an existing class performs the services that a client needs but with different method names. In this situation, you can apply the ADAPTER pattern. The intent of ADAPTER is to provide the interface that a client expects while using the services of a class with a different interface.

Adapting to an Interface

When you need to adapt your code, you may find that the client developer planned well for such circumstances. This is evident when the developer provides an interface that defines the services that the client code needs, as the example in Figure 3.1 shows. A client class makes calls to a RequiredMethod() method that is declared in an interface. You may have found an existing class with a method that can fulfill the client's needs, with a name such as UsefulMethod(). You can adapt the existing class to meet the client's needs by writing a class that extends ExistingClass, implements RequiredInterface, and overrides RequiredMethod() so that it delegates its requests to UsefulMethod().

03fig01.gifFigure 3.1. When a developer of client code thoughtfully defines the client's needs, you may be able to fulfill the interface by adapting existing code.


The NewClass class in Figure 3.1 is an example of ADAPTER. An instance of this class is an instance of RequiredInterface. In other words, the NewClass class meets the needs of the client.

For a more concrete example, suppose you are working with a package that simulates the flight and timing of rockets such as those you manufacture at Oozinoz. The simulation package includes an event simulator that explores the effects of launching several rockets, along with an interface that specifies a rocket's behavior. Figure 3.2 shows this package.

03fig02.gifFigure 3.2. The Simulation package clearly defines its requirements for simulating the flight of a rocket.


Suppose that at Oozinoz you have a PhysicalRocket class that you want to plug into the simulation. This class has methods that supply, approximately, the behavior that the simulator needs. In this situation, you can apply ADAPTER, creating a subclass of PhysicalRocket that implements the IRocketSim interface. Figure 3.3 partially shows this design.

03fig03.gifFigure 3.3. When complete, this diagram shows the design of a class that adapts the Rocket class to meet the needs of the IRocketSim interface.


The PhysicalRocket class has the information that the simulator needs, but its methods do not exactly match those that the simulation declares in the IRocketSim interface. Most of the differences occur because the simulator keeps an internal clock and occasionally updates simulated objects by calling a SetSimTime() method. To adapt the PhysicalRocket class to meet the simulator's needs, an OozinozRocket object can maintain a _time instance variable that it can pass to the methods of the PhysicalRocket class as needed.

Challenge 3.1

Complete the class diagram in Figure 3.3 to show the design of an OozinozRocket class that lets a PhysicalRocket object participate in a simulation as an IRocketSim object.

A solution appears on page 350.

The code for PhysicalRocket is somewhat complex as it embodies the physics that Oozinoz uses to model a rocket. However, it is exactly that logic we want to reuse without reimplementing. The OozinozRocket class simply translates calls to use its superclass's methods. The code for this new subclass will look something like:

public class OozinozRocket : PhysicalRocket, IRocketSim
{
    private double _time;
    public OozinozRocket(
        double burnArea, double burnRate,
        double fuelMass, double totalMass)
        : base (burnArea, burnRate, fuelMass, totalMass)
    {
    }
    public double GetMass()
    {
       // challenge!
    }
    public double Thrust()
    {
        // challenge!
    }
    public void SetSimTime (double time)
    {
        _time = time;
    }
}

Challenge 3.2

Complete the code for the OozinozRocket class, including methods GetMass() and GetThrust().

A solution appears on page 351.

When a client defines its expectations in an interface, you can apply ADAPTER by supplying a class that implements a provided interface and that subclasses an existing class. You may also be able to apply ADAPTER even if no interface exists to define a client's expectations. In this situation, you must use an “object adapter.”

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020