use interfaces if you need multiple inheritance). This article on MSDN offers a good discussion on the topic. Understand that English isn't everyone's first language so be lenient of bad At times, I may have some idea of how my design is going to take shape in future but most of the times I do not have enough clarity to know in advance. Same is not true for interfaces. spelling and grammar. email is in use. Head of Innovation at Collinson Group, Learning something new every day, author of Learning NHibernate 4.0 http://bit.ly/1SoQ3K7.



This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL), I think inheritance supports tight coupling. Love podcasts or audiobooks? Rectangle and Circle inheriting from Shape makes perfect sense here becauseRectangle/Circle are a type of Shape. If you like my article, please dont forget to click to recommend it to others. Think about it: inheritance from a single base class had no alternative but to be tightly coupled!

You can find me on LinkedIn as well. To summarise the recommendations from there and few other articles I have come across, here are the reasons in favour of abstract classes, And these are the reasons in favour of interfaces. By semantics I mean, what definition of an interface fundamentally differentiates it from an abstract class? As your software grows and new features start pouring in, old features keep changing, you would hit a point where you would say to yourself Oh God, I should not have used an abstract class here. First, above recommendations are mostly around syntax a particular language supports and not around semantics (e.g. So, if you do not know which way your software is going to go, there is no way you can base your decision of interface or abstract class on these reasons. All these answers have helped me make a great addition to my knowledge.

20 Bay Street, 11th Floor Toronto, Ontario, Canada M5J 2N8 Interfaces represent capabilities and abstract classes represent type, Implementing interfaces represents can-do relationship and inheriting from (abstract) class represents an is-a relationship, To elaborate this point, lets consider following two classes, Both Camera and Gun can Shoot, that is their capability. Whether I am going to need to inherit from multiple abstract classes or not, Whether there is going to be a default implementation of some contract or not, Whether I would add a new method to a contract or define a new contract entirely in order to implement a change. Cheers!

Java Programming Language: For-Each Loop Example, Convert Excel to CSV or CSV to Excel using Java, Java vs C sharp: Top 8 Important Differences To Know, Use abstract class if you have a default implementation of some behaviour that child classes do not have to implement.

Are they tightly coupled or loosely coupled? Correct me if my understanding is wrong. Also, to be notified about my new articles and stories, follow me on Medium and Twitter.

I get to hear a lot of interesting answers from folks. :laugh: This How about coupling of classes in inheritance? So if you are using an abstract class and need to add a new method to your abstract class, you can happily add that without breaking any code using that class. Thank you for answering first question. Originally published at blog.chatekar.com. +1 (416) 849-8900.

Provide an answer or move on to the next question. It is because the child classes are exposed to the majority of the parent class. Don't tell someone to read the manual. Lately, I have been using below heuristic to determine when to use interfaces/abstract classes and I feel quite excited about it as it works most of the time. If you find that line of thinking difficult, then work out if it is a can-do relationship that you are trying to model or an is-a relationship. So an interface like below would make more sense here, If you have learned OO programming the same way I did, then you would remember the classic shape example as below.

I personally do not believe that these give a complete picture. Second, I feel the above criteria are too futuristic. Instead of trying to predict feature about who will reuse which code, focus on determining whether it is a capability that you are abstracting away or a common type.

But they are both not the same type of things, they are completely different. Chances are they have and don't get it. By that I mean, they all depend on you knowing how your design is going to take shape in future. If a question is poorly phrased then either ask for clarification, ignore it, or.

If there is no default or common behaviour among all the classes that are inheriting from abstract class then interface may be a better choice. Do you need your, CodeProject,

If you google this topic you would find a lot of interesting articles. Prefer abstract classes if your contract has a possibility of changing over time. Learn on the go with our new app. I have been asking this question in interviews for some years now. The content must be between 30 and 50000 characters.