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Inheritance is evil, and must be destroyed: part 1

18 points by danw 19y ago

iamwil 19y ago
The way the author uses the common implementation reminds me of Ruby mixins. One of the things that takes a bit of getting use to in Ruby is that classes aren't types, and object hierarchy is used to share implementation, rather than enforce type.
cstejerean 19y ago
one problem that i have with inheritance, especially several layers deep is that it hides code from the developer and it makes it hard to get an idea of what is going on. A sequence of calls needs to be traced across several class definitions. Sometimes inheritance makes sense as an abstraction mechanism but i think it's often overused, especially in Java
- testapplication 19y ago
  Only a problem if you are browsing your project with notepad.
MuddyMo 19y ago
Very lucid description of one of the major pitfalls (cough) inherent with a strict OOP design structure where the problem domain and/or programming language does not facilitate its imposition.
gills 19y ago
Inheritance is a useful tool. The article mentions the strategy pattern which, ironically, often requires inheritance to implement. So I feel like the author may have been burned and/or confused by inheritance, and following true nerd form has cast it aside completely. Sometimes when you are using a framework, the productivity gained from inheritance cannot be ignored. I suppose this depends on the language and framework design, to a limited extent. That said, I try to compose rather than inherit when possible, as it provides a more opaque implementation.
- dangph 19y ago
  > The article mentions the strategy pattern which, ironically, often requires inheritance to implement. Not really. It only requires interface inheritance for statically-typed languages, which is not really inheritance, and no inheritance at all for duck-typed languages.
mdemare 19y ago
The last couple of years my programming style has changed a lot. I've noticed that I've been using inheritance less and less. When I was still doing Java, I only used (implementation) inheritance when the API forced me to, and now in Ruby I hardly use inheritance at all. I even use objects a lot less - prefering to pass around hashes until they've blossomed into fairly well defined types. To me, a class is a data structure that provides a namespace for the functions that manipulate it, and little more. In any case, I think nearly empty classes with nothing but accessors have no use in dynamic languages (in static languages they provide at least code completion support.) I also increasingly dislike local variables and if-statements (preferring case statements). I like my methods having flow, and if-statements and local variables break that flow, like a caesura in music. What bothers me is that I don't know if this is my progress towards becoming a zen-like programmer, or just me being bored with the old way of doing things, and discovering a new fad. It seems there is no way to tell.
jsjenkins168 19y ago
Compositing should always he used over inheritance where possible, in my opinion. However, claiming inheritance should never be used is a bit unrealistic. There are times when it is a useful and logical choice.

18 points by danw 19y ago

The way the author uses the common implementation reminds me of Ruby mixins. One of the things that takes a bit of getting use to in Ruby is that classes aren't types, and object hierarchy is used to share implementation, rather than enforce type.

cstejerean 19y ago

one problem that i have with inheritance, especially several layers deep is that it hides code from the developer and it makes it hard to get an idea of what is going on. A sequence of calls needs to be traced across several class definitions. Sometimes inheritance makes sense as an abstraction mechanism but i think it's often overused, especially in Java

testapplication 19y ago
Only a problem if you are browsing your project with notepad.

MuddyMo 19y ago

Very lucid description of one of the major pitfalls (cough) inherent with a strict OOP design structure where the problem domain and/or programming language does not facilitate its imposition.

gills 19y ago

Inheritance is a useful tool. The article mentions the strategy pattern which, ironically, often requires inheritance to implement. So I feel like the author may have been burned and/or confused by inheritance, and following true nerd form has cast it aside completely. Sometimes when you are using a framework, the productivity gained from inheritance cannot be ignored. I suppose this depends on the language and framework design, to a limited extent. That said, I try to compose rather than inherit when possible, as it provides a more opaque implementation.

dangph 19y ago
> The article mentions the strategy pattern which, ironically, often requires inheritance to implement. Not really. It only requires interface inheritance for statically-typed languages, which is not really inheritance, and no inheritance at all for duck-typed languages.

mdemare 19y ago

The last couple of years my programming style has changed a lot. I've noticed that I've been using inheritance less and less. When I was still doing Java, I only used (implementation) inheritance when the API forced me to, and now in Ruby I hardly use inheritance at all. I even use objects a lot less - prefering to pass around hashes until they've blossomed into fairly well defined types. To me, a class is a data structure that provides a namespace for the functions that manipulate it, and little more. In any case, I think nearly empty classes with nothing but accessors have no use in dynamic languages (in static languages they provide at least code completion support.) I also increasingly dislike local variables and if-statements (preferring case statements). I like my methods having flow, and if-statements and local variables break that flow, like a caesura in music. What bothers me is that I don't know if this is my progress towards becoming a zen-like programmer, or just me being bored with the old way of doing things, and discovering a new fad. It seems there is no way to tell.

jsjenkins168 19y ago

Compositing should always he used over inheritance where possible, in my opinion. However, claiming inheritance should never be used is a bit unrealistic. There are times when it is a useful and logical choice.