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I have an Access db I use for my checkbook (with a good amount of fairly simple VBA behind it) and I'd like to rewrite it as a stand-alone program with a SQL backend. I'm thinking of using either C++, Java, or Python. I had assumed, before I started, that I would write it OO because I thought that I would think "in OO terms" (due to a OO Logic class and a C++ class I took), but I'm finding that I can only visualize it as procedural (but maybe because I'm mentally stuck in thinking of how the db works in Access). How do I decide? Am I making sense or does it seem like I'm not understanding the concepts?
Thanks for your help.
I'd suggest OO - it's not harder than procedural programming, actually easier to maintain with the right tool. Delphi would be my choice - great DB programming support, visual designer, strongly-typed, plenty of components available. There are many great applications that are written in Delphi. Often underestimated, there are many reasons it's got a loyal following.
Now I'll duck as the Delphi-haters load up with tomatoes.
Well, OO may well be overkill, but it is excellent practice. Any code monkey can write procedural code. Its the path of least resistance in every case, which is why most people use it for one off apps that don't do much. However, if you're writing to get experience in working with OO, than it is best to think of it that way. You could start by designing an object that manages financial transaction, then you will also need a way to interact with the DB. Perhaps you could write a DB layer where you abstract away the database calls from the transaction object using the Entity framework where you could learn LINQ (or whatever the JAVA equivalent is). This is all assuming that you are doing this for fun and practice.
oo seems to be overkill for a simple checkbook app. Try something on a larger scale like something to manage all your financial accounts. This way designing an account class would make sense
Well it depends on your motivation. If you want a checkbook application as quickly as possible, just churn out the procedural code. No-one other than you will know the difference. If you want to use this application to better yourself as aprogrammer. Take the time to learn how to write in in OO.
I'd go with Python: no compiling and uses dynamic typing (you can use strict typing too if you want). Plus, it has a huge following in the open source community which means great support, tools, and documentation for free.
As for OO vs. Procedural -- all these languages you've mentioned could be written in a procedural style -- that is, one big class/method that does everything -- but you'll soon find that you'll want to follow DRY principles (Don't Repeat Yourself) and start with some private methods that do one particular thing well. From then, you'll want to group similar things into separate classes, and then from there you'll want to abstract those classes... see where I'm going here?
In my opinion you should concentrate less on the OO versus procedural thing. If you have the possibility to go procedural in the beginning, then go procedural. It's the easiest thing you can do to get you started. The OO thing, on the other hand, may just as well qualify as YAGNI (You Ain't Gonna Need It).
What you should do though, is to write tests, unit tests and then integration tests. And you should strive to write tests first. This way, even if you begin with a procedural application you may later on refactor it into a full-fledged OO application. But, only if you need objects. These tests will be you're safety net when moving around code in your application.
Trying to think your applications into object from the beginning may lead you to an point where you're stuck with your class hierarchies and architecture.
I'm not a genius, so I may be wrong, but in my experience, starting with simple functions and then thinking about grouping them into objects or modules is better than starting by saying: OK, I'll have this object that interacts with this object, which is implementing pattern X, so this way I'll decouple interface Y from implementation Z. Later on, you may observe that your domain model is weak. Take an evolutionary design path and start with small building blocks.
If you are looking for a quick app that you can extend, check out Dynamic Data.
Lately, I've been making use a lot of the Strategy Pattern along with the Factory Pattern. And I really mean a lot. I have a lot of "algorithms" for everything and factories that retrieve algorithms based on parameters.
Even though the code seems very extensible, and it is, having N factories seems a bit of an abuse.
I know this is pretty subjective, and we're talking without seeing code, but is this acceptable in real world code? Would you change something ?
OK- ask yourself a question. does/will this algorithm implementation ever change? If no then remove the strategy.
I am maintence.
I once was forced (by my pattern lovin' boss) to write a set of 16 "buffer interpreter tuxedo services" using an AbstractFactory and a double DAO pattern in C++ (no reflections, no code gen). All up it something like 20,000 lines of the nastiest code I've even seen (not the least because I didn't really know C++ when I started) and it took about three months.
Since my old boss has moved on I've rewritten them using good 'ole "straight up and down" procedural style C++, with couple of funky-macros... each service is like 60 lines of code, times 16... all up less than a 1000 lines of really SIMPLE code; so simple that even I can follow it.
Cheers. Keith.
Whenever I'm implementing code in this fashion, some questions I ask are:
what components do I need to substitute to test ?
what components will I expect users/admins to disable or substitute (e.g. via Spring configs or similar) ?
what components do I expect or suspect will not be required in the future due to (possibly) changing requirements ?
This all drives how I construct object or components (via factories) and how I implement algorithms. The above is vague, but (of course) the requirements can be similarly difficult to pin down. Without seeing your implementation and your requirements, I can't comment further, but the above should act as some guideline to help you determine whether what you've done is overkill.
If you're using the same design pattern all over the place, perhaps you should either switch to a language that has better support for what you're trying to do or rethink your code to be more idiomatic in your language of choice. After all, that's why we have more than one programming language.
Would depends on the kind of software I'm working on.
Maintenance asks for simple code and factories is NOT simple code.
But extensibility asks sometimes for factories...
So you have to take both in consideration.
Just have in mind that most of the time, you will have to maintain a source file MANY times a year and you will NOT have to extend it.
IMO, patterns should only be used when absolutely needed. If you think it can be handy in two years, you are better to use them... in two years.
How complex is the work the factory is handling? Does object creation really need to be abstracted to a different class? A variation of the factory method is having a simple, in-class factory. This really works best if any dependencies have already been injected.
For instance,
public class Customer
{
public Customer CreateNewCustomer()
{
// handle minimally complex create logic here
}
}
As far as Strategy overuse... Again, as #RichardOD explained, will the algorithm ever really change?
Always keep in mind the YAGNI principle. You Aren't Gonna Need It.
Can't you make an AbstractFactory instead off different standalone factories?
AlgorithmFactory creates the algorithms you need based on the concrete factory.
I recently had a debate with a colleague who is not a fan of OOP. What took my attention was what he said:
"What's the point of doing my coding in objects? If it's reuse then I can just create a library and call whatever functions I need for whatever task is at hand. Do I need these concepts of polymorphism, inheritance, interfaces, patterns or whatever?"
We are in a small company developing small projects for e-commerce sites and real estate.
How can I take advantage of OOP in an "everyday, real-world" setup? Or was OOP really meant to solve complex problems and not intended for "everyday" development?
My personally view: context
When you program in OOP you have a greater awareness of the context. It helps you to organize the code in such a way that it is easier to understand because the real world is also object oriented.
The good things about OOP come from tying a set of data to a set of behaviors.
So, if you need to do many related operations on a related set of data, you can write many functions that operate on a struct, or you can use an object.
Objects give you some code reuse help in the form of inheritance.
IME, it is easier to work with an object with a known set of attributes and methods that it is to keep a set of complex structs and the functions that operate on them.
Some people will go on about inheritance and polymorphism. These are valuable, but the real value in OOP (in my opinion) comes from the nice way it encapsulates and associates data with behaviors.
Should you use OOP on your projects? That depends on how well your language supports OOP. That depends on the types of problems you need to solve.
But, if you are doing small websites, you are still talking about enough complexity that I would use OOP design given proper support in the development language.
More than getting something to just work - your friend's point, a well designed OO design is easier to understand, to follow, to expand, to extend and to implement. It is so much easier for example to delegate work that categorically are similar or to hold data that should stay together (yes even a C struct is an object).
Well, I'm sure a lot of people will give a lot more academically correctly answers, but here's my take on a few of the most valuable advantages:
OOP allows for better encapsulation
OOP allows the programmer to think in more logical terms, making software projects easier to design and understand (if well designed)
OOP is a time saver. For example, look at the things you can do with a C++ string object, vectors, etc. All that functionality (and much more) comes for "free." Now, those are really features of the class libraries and not OOP itself, but almost all OOP implementations come with nice class libraries. Can you implement all that stuff in C (or most of it)? Sure. But why write it yourself?
Look at the use of Design Patterns and you'll see the utility of OOP. It's not just about encapsulation and reuse, but extensibility and maintainability. It's the interfaces that make things powerful.
A few examples:
Implementing a stream (decorator pattern) without objects is difficult
Adding a new operation to an existing system such as a new encryption type (strategy pattern) can be difficult without objects.
Look at the way PostgresQL is
implemented versus the way your
database book says a database should
be implemented and you'll see a big
difference. The book will suggest
node objects for each operator.
Postgres uses myriad tables and
macros to try to emulate these nodes.
It is much less pretty and much
harder to extend because of that.
The list goes on.
The power of most programming languages is in the abstractions that they make available. Object Oriented programming provides a very powerful system of abstractions in the way it allows you to manage relationships between related ideas or actions.
Consider the task of calculating areas for an arbitrary and expanding collection of shapes. Any programmer can quickly write functions for the area of a circle, square, triangle, ect. and store them in a library. The difficulty comes when trying to write a program that identifies and calculates the area of an arbitrary shape. Each time you add a new kind of shape, say a pentagon, you would need to update and extend something like an IF or CASE structure to allow your program to identify the new shape and call the correct area routine from your "library of functions". After a while, the maintenance costs associated with this approach begin to pile up.
With object-oriented programming, a lot of this comes free-- just define a Shape class that contains an area method. Then it doesn't really matter what specific shape you're dealing with at run time, just make each geometrical figure an object that inherits from Shape and call the area method. The Object Oriented paradigm handles the details of whether at this moment in time, with this user input, do we need to calculate the area of a circle, triangle, square, pentagon or the ellipse option that was just added half a minute ago.
What if you decided to change the interface behind the way the area function was called? With Object Oriented programming you would just update the Shape class and the changes automagically propagate to all entities that inherit from that class. With a non Object Oriented system you would be facing the task of slogging through your "library of functions" and updating each individual interface.
In summary, Object Oriented programming provides a powerful form of abstraction that can save you time and effort by eliminating repetition in your code and streamlining extensions and maintenance.
Around 1994 I was trying to make sense of OOP and C++ at the same time, and found myself frustrated, even though I could understand in principle what the value of OOP was. I was so used to being able to mess with the state of any part of the application from other languages (mostly Basic, Assembly, and Pascal-family languages) that it seemed like I was giving up productivity in favor of some academic abstraction. Unfortunately, my first few encounters with OO frameworks like MFC made it easier to hack, but didn't necessarily provide much in the way of enlightenment.
It was only through a combination of persistence, exposure to alternate (non-C++) ways of dealing with objects, and careful analysis of OO code that both 1) worked and 2) read more coherently and intuitively than the equivalent procedural code that I started to really get it. And 15 years later, I'm regularly surprised at new (to me) discoveries of clever, yet impressively simple OO solutions that I can't imagine doing as neatly in a procedural approach.
I've been going through the same set of struggles trying to make sense of the functional programming paradigm over the last couple of years. To paraphrase Paul Graham, when you're looking down the power continuum, you see everything that's missing. When you're looking up the power continuum, you don't see the power, you just see weirdness.
I think, in order to commit to doing something a different way, you have to 1) see someone obviously being more productive with more powerful constructs and 2) suspend disbelief when you find yourself hitting a wall. It probably helps to have a mentor who is at least a tiny bit further along in their understanding of the new paradigm, too.
Barring the gumption required to suspend disbelief, if you want someone to quickly grok the value of an OO model, I think you could do a lot worse than to ask someone to spend a week with the Pragmatic Programmers book on Rails. It unfortunately does leave out a lot of the details of how the magic works, but it's a pretty good introduction to the power of a system of OO abstractions. If, after working through that book, your colleague still doesn't see the value of OO for some reason, he/she may be a hopeless case. But if they're willing to spend a little time working with an approach that has a strongly opinionated OO design that works, and gets them from 0-60 far faster than doing the same thing in a procedural language, there may just be hope. I think that's true even if your work doesn't involve web development.
I'm not so sure that bringing up the "real world" would be as much a selling point as a working framework for writing good apps, because it turns out that, especially in statically typed languages like C# and Java, modeling the real world often requires tortuous abstractions. You can see a concrete example of the difficulty of modeling the real world by looking at thousands of people struggling to model something as ostensibly simple as the geometric abstraction of "shape" (shape, ellipse, circle).
All programming paradigms have the same goal: hiding unneeded complexity.
Some problems are easily solved with an imperative paradigm, like your friend uses. Other problems are easily solved with an object-oriented paradigm. There are many other paradigms. The main ones (logic programming, functional programming, and imperative programming) are all equivalent to each other; object-oriented programming is usually thought as an extension to imperative programming.
Object-oriented programming is best used when the programmer is modeling items that are similar, but not the same. An imperative paradigm would put the different kinds of models into one function. An object-oriented paradigm separates the different kinds of models into different methods on related objects.
Your colleague seems to be stuck in one paradigm. Good luck.
To me, the power of OOP doesn't show itself until you start talking about inheritance and polymorphism.
If one's argument for OOP rests the concept of encapsulation and abstraction, well that isn't a very convincing argument for me. I can write a huge library and only document the interfaces to it that I want the user to be aware of, or I can rely on language-level constructs like packages in Ada to make fields private and only expose what it is that I want to expose.
However, the real advantage comes when I've written code in a generic hierarchy so that it can be reused later such that the same exact code interfaces are used for different functionality to achieve the same result.
Why is this handy? Because I can stand on the shoulders of giants to accomplish my current task. The idea is that I can boil the parts of a problem down to the most basic parts, the objects that compose the objects that compose... the objects that compose the project. By using a class that defines behavior very well in the general case, I can use that same proven code to build a more specific version of the same thing, and then a more specific version of the same thing, and then yet an even more specific version of the same thing. The key is that each of these entities has commonality that has already been coded and tested, and there is no need to reimpliment it again later. If I don't use inheritance for this, I end up reimplementing the common functionality or explicitly linking my new code against the old code, which provides a scenario for me to introduce control flow bugs.
Polymorphism is very handy in instances where I need to achieve a certain functionality from an object, but the same functionality is also needed from similar, but unique types. For instance, in Qt, there is the idea of inserting items onto a model so that the data can be displayed and you can easily maintain metadata for that object. Without polymorphism, I would need to bother myself with much more detail than I currently do (I.E. i would need to implement the same code interfaces that conduct the same business logic as the item that was originally intended to go on the model). Because the base class of my data-bound object interacts natively with the model, I can instead insert metadata onto this model with no trouble. I get what I need out of the object with no concern over what the model needs, and the model gets what it needs with no concern over what I have added to the class.
Ask your friend to visualize any object in his very Room, House or City... and if he can tell a single such object which a system in itself and is capable of doing some meaningful work. Things like a button isnt doing something alone - it takes lots of objects to make a phone call. Similarly a car engine is made of the crank shaft, pistons, spark plugs. OOPS concepts have evolved from our perception in natural processes or things in our lives. The "Inside COM" book tells the purpose of COM by taking analogy from a childhood game of identifying animals by asking questions.
Design trumps technology and methodology. Good designs tend to incorporate universal principals of complexity management such as law of demeter which is at the heart of what OO language features strive to codify.
Good design is not dependant on use of OO specific language features although it is typically in ones best interests to use them.
Not only does it make
programming easier / more maintainable in the current situation for other people (and yourself)
It is already allowing easier database CRUD (Create, Update, Delete) operations.
You can find more info about it looking up:
- Java : Hibernate
- Dot Net : Entity Framework
See even how LINQ (Visual Studio) can make your programming life MUCH easier.
Also, you can start using design patterns for solving real life problems (design patterns are all about OO)
Perhaps it is even fun to demonstrate with a little demo:
Let's say you need to store employees, accounts, members, books in a text file in a similar way.
.PS. I tried writing it in a PSEUDO way :)
the OO way
Code you call:
io.file.save(objectsCollection.ourFunctionForSaving())
class objectsCollection
function ourFunctionForSaving() As String
String _Objects
for each _Object in objectsCollection
Objects &= _Object & "-"
end for
return _Objects
end method
NON-OO Way
I don't think i'll write down non-oo code. But think of it :)
NOW LET'S SAY
In the OO way. The above class is the parent class of all methods for saving the books, employees, members, accounts, ...
What happens if we want to change the way of saving to a textfile? For example, to make it compactible with a current standard (.CVS).
And let's say we would like to add a load function, how much code do you need to write?
In the OO- way you only need the add a New Sub method which can split all the data into parameters (This happens once).
Let your collegue think about that :)
In domains where state and behavior are poorly aligned, Object-Orientation reduces the overall dependency density (i.e. complexity) within these domains, which makes the resulting systems less brittle.
This is because the essence of Object-Orientation is based on the fact that, organizationally, it doesn't dustinguish between state and behavior at all, treating both uniformly as "features". Objects are just sets of features clumpled to minimize overall dependency.
In other domains, Object-Orientation is not the best approach. There are different language paradigms for different problems. Experienced developers know this, and are willing to use whatever language is closest to the domain.
What do you suggest for Data Access layer? Using ORMs like Entity Framework and Hibernate OR Code Generators like Subsonic, .netTiers, T4, etc.?
For me, this is a no-brainer, you generate the code.
I'm going to go slightly off topic here because there's a bigger underlying fallacy at play. The fallacy is that these ORM frameworks solve the object/relational impedence mismatch. This claim is a barefaced lie.
I find the best way to resolve the object/relational impedance mismatch is to either use OOP exclusively and use an object database or use the idioms of the relational database exclusively and ignore OOP.
The abstraction "everything is a table" is to me, much more powerful than the abstraction "everything is a class." It takes less code, less intellectual effort and leads to faster code when you code to the database rather than to an object model.
To me this seems obvious. If your application is data driven then surely your code should be data driven too? Yet to say this is hugely controversial.
The central problem here is that OOP becomes a really leaky abstraction when used in conjunction with a database. Code that look perfectly sensible when written to the idioms of OOP looks completely insane when you see the traffic that code generates at the database. When that messiness becomes a performance problem, OOP is the first casualty.
There is really no way to resolve this. Databases work with sets of data. OOP focus on instances of classes. Trying to marry the two is always going to end in divorce.
So to answer your question, I believe you should generate your classes and try and make them map the underlying database structure as closely as possible.
Perhaps controversially, I've always felt that using code generators for the ADO.NET plumbing is fundamentally solving the wrong problem.
At some point, hopefully not too long after learning about Connection Strings, SqlCommands, DataAdapters, and all that, we notice that:
Such code is ugly
It is very boring to write
It's very easy to miss something if you're doing it by hand
It has to be repeated every time you want to access the database
So, the problem to solve is "how to do the same thing lots of times fast"?
I say no.
Using code generators to make this process quick still means that you have a ton of code, all the same, all over your business classes (or your data access layer, if you separate that from your business logic).
And then, if you want to do something generically (like track stored procedure usage, for instance), you end up having to customise your code generator if it doesn't already have the feature you want. And even if it does, you still have to regenerate everything all the time.
I like to do things once, not many times, no matter how fast I can do them.
So I rolled my own Data Access class that knows how to add parameters, set up and close connections, manage transactions, and other cool stuff. It only had to be written once, and calling its methods from a Business object that needs some database stuff done consists of one line of code.
When I needed to make the application support multithreaded database accesses, it required a change to the Data Access class only, and all the business classes just do what they already did.
There is no right answer it all depends on your project. As Simon points out if your application is all data driven, then it might make sense depending on the size and complexity of the domain to use non oop paradigm. I had a lot of success building a system using a Transaction Script pattern, which passed XML Messages around the system.
However this system started to break down after five or six years as the application grew in size and complexity (5 or 6 webs, several web services, tons of COM+ components, legacy and .net code, 8+ databases with 800+ tables 4,000+ procedures). No one knew what anything was, and duplication was running rampant.
There are other ways to alleviate the maintance then OOP; however, if you have a very complex domain then hainvg a rich domain model is ideal IMHO, as it allows for the business rules to be expressed in nice encapsulated components.
To answer your question, avoid code generators if you can. Code generators are a recipe for disaster, but if you do go with code generation do not modify the generated code. Also be sure to have a good process in place that is easy for developers to get the new generated code.
I recommend using either the following: ORM or hand roll a lightweight DAL. I am currently transitioning a project over to nHibernate off my hand rolled DAL and am having a lot of success; however, I like having the option of using either option. Further if you properly seperate your concerns (Data Access from Business Layer from Presentation) you can have a single service layer that might talk to a Dao (Data Access Object) that for one object is an ORM but for another is hand rolled). I like this flexibility as it allows to apply the best tool to the job.
I like nHibernate over a hand rolled DAL because while my DAL does abstract away most of the ADO.Net code you still have to write the code that takes a data reader to an object or an object and creates the parameters.
I've always preferred to go the code generator route, especially in C# where you can make use of extended classes to add functionality to the basic data objects.
Hate to say this, but it depends. If you find an ORM tool that fits your needs go for it. We wrote our own system in small steps while developing the application. We are using C++ and there are not that many tools out there anyway. Ours ended up being a XML description of the database, from that the SQL generation script and the basic object layer and metadata were generated.
Do your homework and evaluate theses tools and you will find a good fit for your needs.
I've read a lot of people saying that some things shouldn't be written in an object orientated style - as a person learning the OO style coming from a C background, what do they mean by this?
What shouldn't be OO, why do some things fit this design better, and how do we know when it's best to do what?
The real world is full of objects.
It's helpful to make the software world match the real world.
"What about 'system utilities'? They just deal with abstractions like sockets and processes and file systems." They sound like things to me. They have attributes and behaviors, they have associations.
If you're looking for proof that OO is better, there isn't any. Nothing is better because better is a gloriously vague term. Anyone who's clever can write any program in any style. You could adopt functional, procedural, object-oriented, or anything you feel like.
I use OO because I have a very small brain and must learn to live within its limits. OO is a crutch to help me struggle through programming. If I was smarter, richer and better-looking, I wouldn't need the help, and I could write non-OO programs. Sadly, I'm not smart. Without class definitions to isolate responsibility and structure an architecture, I'd still be writing single-file "hello world" variants.
A simple rule of thumb is to encapsulate complex data and repeatedly used code, and to ignore what isn't. This lets you put complicated data structures together with their manipulative methods for greater portability and flexibility. Such as a list of database objects with intelligent sorting by property type.
OO code also obfuscates what you don't need to know. Such as, I don't need to know what my sort algorithm is until it slows me down, or if I'm already programming for a high performance environment.
Another great thing about OO code is its polymorphism, the way you can use subsequent types to change actions without the program knowing how or caring about it. An example is an archive format with multiple file-list types: the list may have an array of structures (records or structs) within it that changes between the types of list, but inherit from a base class and the complexity of knowing which underlying structure to use goes away. It would be quite difficult to manage that without object orientation, and quite frankly it's tough enough to manage as it is with object orientation.
OO and MVC do not solve your problems if you don't know how to solve them already, they merely give you more powerful ways to shoot yourself in the foot—only this time you might not know why. So remember that if it's anything, OO isn't the "magic bullet" ... but remember that it can be the magic bullet given the right situation and the right programmer.
Object Oriented design is all about managing complexity as your system grows. Therefore OO design can be overkill for smaller less complex systems, or for systems that you know will never grow.
Of course the problem is that we rarely know with certainty that a system is not going to grow.
I agree with most of the above (or below?) that OO exists to simplify complex problems and software design.
However, there are many times where it is extremely overdone. I can't tell you the number of times where I wish there was a Visual Studio Unrefactor button just to make sense of the code and put all base classes in one file for readability.
I can't think of anything other than stored procedures. Get yourself a copy of Reflector and use it to look at the .NET framework dll's as a good learning lesson. Alternately there are a ton of books on C++ and OO on the market since thats been around a while.
If you're writing mobile applications (at least I can speak for .NET mobile), then you should try to be as non-OO as possible. As much as mobile has advanced, you don't want to waste system memory because you've tied up processing with abstraction layers, large datasets in memory, or other entities that will slow things down. You'll want to write things as straightforward as possible.
Just a tip: you should tag this question as "subjective" as everyone seems to have a different opinion on things like this.