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Firmware developement follow different rules than software, there's no circling around it. Software should not depend on the underlying implementation details, firmware is the underlying implementation and it's all about details.
Some things should be kept as agnostic as possible, e.g. the main state machine should not depend on the exact make of the various hardware components so interfaces to control hardware should be generic (i.e. peripheral_On, peripheral_Off, peripheral_Sleep, peripheral_Send...) but all the rest can not. One component may be turned on/off via the combination of two pins while another, identical on every aspect, may require timed pulses on a single pin and follow a protocol based on several outputs.
GCS d--(d+) s-/++ a C++++ U+++ P- L+@ E-- W++ N+ o+ K- w+++ O? M-- V? PS+ PE- Y+ PGP t+ 5? X R+++ tv-- b+(+++) DI+++ D++ G e++ h--- r+++ y+++* Weapons extension: ma- k++ F+2 X
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Yeah. Reality bites.
At some point we try to abstract away all the hardware bit stuffing, but it's still there ruining all the nice plans - all it needs is an auto resetting status bit when other bits in the byte are read to ruin everything.
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heap allocation at run-time is something brutally beat into me. actually beat out of me.
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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My theory is that there are very few examples around that bring OOP all together.
OOPs main purpose should be reuse and making the code that you write smaller (less code to deal with when adding enhancements or fixing bugs).
I believe that with one very focused example you would see all of PIE-A (Polymorphism, Inheritance, Encapsulation and Abstraction) come together.
But most of the time you don't need this type of architecture until things get large. And, most projects don't get large -- especially samples you see.
Here's My Attempt
This should be an article but I'll do that later.
The Entire Premise
Imagine you want to save data to three different data stores:
1) file
2) database
3) web location
Save instantly becomes our main verb(functionality).
Requirements: We Want Four Things
1. Any dev must be able to include the Save() functionality on their class in the future. (interface)
2. Any dev must be able to call the Save() functionality on any class in the future and easily know that it is named Save() -- this is self-documenting code
3. There must be an easy way for dev to configure where the data will be stored (file, db, url)
4. A dev must be able to create a list of various types (classes in the architecture) and iterate through them, calling Save() and knowing that they will save to their appropriate destination. This is Polymorphism -- all objects implement the Interface which provides Save().
Here is the smallest sample I can come up with and it really works.
Get LINQPad - The .NET Programmer's Playground[^] and run the code below.
You will see the following output:
I'm saving into a FILE : super.txt
I'm saving into a FILE : extra.txt
I'm saving into a DATABASE : connection=superdb;integrated security=true
I'm saving into a WEB LOCATION : http:
I'm saving into a FILE : super.txt
I'm saving into a FILE : extra.txt
I'm saving into a DATABASE : connection=superdb;integrated security=true
I'm saving into a WEB LOCATION : http:
Now a dev can
1. create an IPersistable object.
2. pass in an IConfigurable object (which determines which data store the Save() will write to
3. call Save() on the object
Dev Only Needs To Know Two Things: Abstraction
1. create a configurable object -- select which data store
2. call Save()
void Main()
{
List<IPersistable<IConfigurable>> allItems = new List<IPersistable<IConfigurable>>();
FileConfig fc = new FileConfig("super.txt");
IPersistable<IConfigurable> item = new FileSaver(fc);
List<IPersistable<IConfigurable>> fakeData = new List<IPersistable<IConfigurable>>();
fakeData.Add(new FileSaver(new FileConfig("extra.txt")));
fakeData.Add(new DatabaseSaver(new DatabaseConfig("connection=superdb;integrated security=true")));
fakeData.Add(new TcpSaver(new TcpConfig("http://test.com/saveData?")));
allItems.Add(item);
foreach (IPersistable<IConfigurable> ic in fakeData){
allItems.Add(ic);
}
foreach (IPersistable<IConfigurable> ip in allItems)
{
ip.Save();
}
foreach (var ip in allItems)
{
ip.Save();
}
}
interface IPersistable<T> where T : IConfigurable {
bool Save();
}
interface IConfigurable {
}
class FileSaver : IPersistable<IConfigurable>{
protected FileConfig config;
public FileSaver(FileConfig config){
this.config = config;
}
virtual public bool Save(){
Console.WriteLine(String.Format("I'm saving into a FILE : {0}",config.FileName));
return true;
}
}
class FileConfig : IConfigurable{
public string FileName{get;set;}
public FileConfig(String fileName=null){
FileName = fileName;
}
}
class DatabaseConfig : IConfigurable{
public string ConnectionString{get;set;}
public DatabaseConfig(String ConnectionString=null){
this.ConnectionString = ConnectionString;
}
}
class TcpConfig : IConfigurable{
public string Uri {get;set;}
public TcpConfig(String uri){
Uri = uri;
}
}
class DatabaseSaver : IPersistable<IConfigurable>{
protected DatabaseConfig config;
public DatabaseSaver(DatabaseConfig config){
this.config = config;
}
public bool Save(){
Console.WriteLine(String.Format("I'm saving into a DATABASE : {0}", config.ConnectionString));
return true;
}
}
class TcpSaver : IPersistable<IConfigurable>{
TcpConfig config;
public TcpSaver(TcpConfig config){
this.config = config;
}
public bool Save(){
Console.WriteLine(String.Format("I'm saving into a WEB LOCATION : {0}", config.Uri));
return true;
}
}
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I also worked in what you could call the embedded world, though not so close to the hardware, and soft rather than hard real-time. An OO rewrite saved the product I was working on, and it's still seeing development over 20 years later. We used all three (encapsulation, inheritance, and polymorphism) extensively.
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The farther you get from the hardware the more generalized approach are useful / a necessity. I worked in a product with similar specifications ("not so close to the hardware, and soft rather than hard real-time.") and OOP was a huge benefit, when we started adopting it there has been a significant improvement in quality, developement time, customization time and stability.
GCS d--(d+) s-/++ a C++++ U+++ P- L+@ E-- W++ N+ o+ K- w+++ O? M-- V? PS+ PE- Y+ PGP t+ 5? X R+++ tv-- b+(+++) DI+++ D++ G e++ h--- r+++ y+++* Weapons extension: ma- k++ F+2 X
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You are quite correct, IMO. First, forget about the promise of re-use when it comes to objects. Nobody ever does anything in the real world twice exactly the same way to merit any re-use benefit.
In order of importance, to me:
1. Encapsulation - keeps stuff organized
2. Interfaces - defines what the class is expected to implement. I also use empty interfaces simply to indicate that the class supports some other behavior. Could use attributes for that as well, but interfaces are sometimes more convenient when dealing with a collection of classes that all support the same thing and there are methods that operate on that, hence I can pass in "IAuditable", for example.
3. Inheritance/Abstraction - mostly useless, but there are times when I want to pull out common properties among a set of logical classes. Note that I don't consider this to be true abstraction, it's using inheritance to defined common properties and behaviors.
4. Polymorphism - useful, but less so now with optional default parameters that do the work of what one often used polymorphic methods for.
IMO, the reality of "how useful is OO" falls quite short of the promise of OO.
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I'd agree. Sounds like function interfaces with better, purposeful, naming of the why, rather than a focus on the what & how.
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I tend to take the view that isolation is a good target. Code isolated from other code is both maintainable and reusable, regardless of whether it is via an OO design or not.
Reuse is limited when using any OO language, because then any program that wants to reuse that code has to use the same language. If you're going after reuse, you have to give up OO because they are mutually exclusive.
All the re-used code are written in a non-OO language. Sqlite, for example, is one of the most widely deployed pieces of code in the world. All media format readers, as well, are widely deployed and non-OO.
If you write something really new and novel that does not exist (a new image format, a new protocol, new encryption algo, new compression format, interface to any of the above, or interface to existing daemons (RDBMSs, etc)), and you write it in Java or C#, the only way that it can become popular is if someone re-implements it in C so that Python, C, C++, Java, C#, Delphi, Lazarus, Perl, Rust, Go, Lisps, Php, Ruby, Tcl (and more) programs can use it.
The upside of producing library files (.so or .dll) that can be used by any language is that the result is also quite isolated and loosely coupled from anything else:
- It can be be easily extended by anyone, but not easily enhanced.
- It can be easily swapped out and replaced with a different implementation without needing the programs using that library to be recompiled, redeployed or changed in any way.
- Because it is a library, it will only be for a single type of task (no one would even think of putting unrelated functionality into a compression library, but I've seen devs happily put in unrelated stuff into a compression class).
Ironically, you can more easily achieve SOLID principles writing plain C libraries (.so or .dll) than you can with actual OO languages, because of the limitations of the call interface in dynamic libraries.
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fwiw, the code I am modifying has not changed in 10 years. So, why bother making it general?
Well, if it has not changed in 10 years I would say it is general enough
I am in sort of the same place as you. Mostly embedded development, and whenever I tried using OO I mostly failed. Usually because I decide to make a class for something that will only have one object instance.
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NelsonGoncalves wrote: Usually because I decide to make a class for something that will only have one object instance.
Usually, when I see that a class is instantiated only once, like some sort of singleton, I always think it might be wise to drop the class and put everything in a namespace.
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Yes, I agree. But I start with the "everything is an object" mentality, and only latter do I recognize that, for my applications, most of the times that is the wrong way to think.
I could spend 1hr thinking on the design, but that would just prevent me from latter spending 2 days fixing bad design decisions
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I know where you are coming from but would think it depends on what you are working on. some projects and cases may merit it and some not, and although i dont work in embedded would assume that it's less important. however as a 'business app guy' i find it great, however if i really looked at it i probably don't need it as much as i think i do, but it's the way i roll now and i quite like it GL
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I do embedded firmware full time. We use all of the OO features you have mentioned. For the most part this has been done as a positive effort, ie it was worth the effort. But lately I think we have taken it too far and the code is too difficult to follow and debug and also our performance seems really bad. We are now in the process of going back (yet again) to profile, study and do performance measurements.
But I think it is a case of having too much of a good thing. We have overused such features on an embedded design with limited memory and tight timing requirements.
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Just wondering: Are you implementing a higher level design model provided by others, or doing the higher level design model yourself, or implementing the design idea directly?
The source of the design often impacts the firmware implementation approach (i.e. if/how Model Based Systems Engineering MBSE is being done).
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We build everything from ground up including custom ASICs.
But we have a large development team, maybe in the 100's.
But what seems to be happening as a trend is an over use of language features. Or in another perspective the solutions are over-engineered. I have seen developers resort to techniques that are perfectly fine in a PC application environment where you have Gigahertz processors and Gigs of RAM
But in a custom hardened, real-time, constrained embedded systems the environment is different.
While the tools will support C++ templates, all the OO features etc, there is an art to how to balance design freedom vs efficient execution.
You can definitely use OO features in this environment, we have done it successfully before.
But there is risk of going too far and again this is where experience comes into play.
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Sounds about right. The Object Orientation does remove the designer (software or hardware) from the lower level realities and limitations.
If folks haven't had the experience of working within those limitations then they have a hard time designing for them. They have been set-up (oriented) to keep the problems behind them!
I blame Matlab
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My Opinion (Based on experience),
Every implementation of Polymorphism, on every team that used it, goes sideways pretty quickly, and becomes quite chore to maintain.
OOP principles are generally sound, but I have not even considered using Polymorphism in 20 years.
Mainly because its harder to debug.
BUG:
"The Investor Customer is disturbing the customerChecking balance because they customer is also an investor" - Resulting in the loss of his mortgage.
Keep It Simple, keep it moving.
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The real problem with OO Programming and possibly Design is that everyone knows the parts, but most don't put them together well. OO has worked well for years and it is visible at the low level.
Consider the storage device. It can be a floppy (remember those?), a hard drive, an SSD, a write once, CD/DVD, an online storage, an so many more. But the block storage protocol is applied to all. the Driver converts the hardware to an object that responds to the same inputs no matter what is hidden behind the interface. The device is the object. The functionality is abstracted and hidden. The behavior is locked behind the wall. And the new types of devices are added invisibly to the higher levels of code by following the interface rules. Enhancements to the rules are added all the time by extending the interface for things that were not previously considered.
The trick is in creating the specific, but only working with the generic. The failure is in creating specific necessary behavior at the derived level that cannot be used at the generic level.
Hierarchy of Animal -> Quadruped -> Horse.
Horse whinnies and gallops. But to implement them as Horse features means that they must be addressed as features of a horse.
Instead, Animal Speaks(Friendly | Loudly | Fearfully ), Moves( Slowly | Quickly )
Now, we can say Animal->Speak(Friendly), Animal->Moves( Quickly).
We can add Dog and a Cat and implement the interface described. Then we create the item and put it in Animal and use it without changing the code at all.
The biggest trick of all, is to construct the Animal (or derived type) with as much of the descriptive information as possible. then use it with as little information as possible.
Compare to the original Storage idea. the File Create and Open takes all kinds of descriptive information, but the actions on it take only the necessary variations. File->Read( howMuch, toWhere). File->Seek(toPosition, fromWhere).
It isn't really the tenants of OO that are in question, it is the organization. Put them together and use them well and they provide for an easier path to expansion, adaptation and improvements.
Print is a great example of Polymorphism.
Print (integer)
Print (string)
Print (float)
Print (format, arg1, arg2, arg3, ...)
Print (Animal)
OO is more than a Hammer. It is a whole Toolbox than can be used to build better tools and expandable structures.
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I actually have a complex example of when inheritance should have been used, but wasn't. We have a Posi-Pay application that basically takes check and deposit data from a bank and converts it to something we can use. The program has a 15k+ lines long switch statement, one case for each bank format. Much of the code is duplicated among case statements. The unique licensing code is in a separate area, but also is a giant switch statement.
I long for the day when I'll be given the time to make each bank format a separate class, the base class would have all the conversion functions needed, and the switch statements become 1 line of code each:
BankFormat.Convert(<bank format type>)
BankFormat.GetLicense(<bank format type>)
Bond
Keep all things as simple as possible, but no simpler. -said someone, somewhere
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I agree. Behind the OO curtain lies a bunch of functions.
I have made and used them, but always with my code running behind the scenes.
I work 99% in Windows - How much simpler could this function be?
function -> SEND_EMAIL(STRUCTURE)
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In embedded environments I'm not sure a lot of the OOD stuff makes sense.
Encapsulation - definitely as it hides the intricacies of the hardware, but be careful you don't introduce performance penalties by doing so.
Abstraction - goes along with encapsulation in this case with the same caveats.
Inheritance - depends on the application. Don't use it just because it's available. I have used Inheritance successfully, but going more than two or three levels deep simply invites inefficiencies and unreadable code. Consider that most unreadable code is because the control flow is at the wrong level and then consider that inheritance is a form of control flow.
Polymorphism - use it or don't use it as needed.
In other words, you don't have to use all of OOD if it doesn't make sense. Use what makes sense.
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I still mainly like OO stuff (as a .NET/C# dev), but I can't say whether your project would benefit from the refactoring you considered. If your gut says no, then I believe you.
I come across useful inheritance examples occasionally, so I don't understand inheritance hate. Like any language feature it can be abused. My examples are often abstract classes that therefore require another class to implement/inherit abstract methods. For example, I work on stuff that I want to work equally well in a local file system and Azure blob storage. There is some common behavior that goes in an abstract base class, followed by some subclass capabilities that are environment-specific. From the .NET BCL, Streams follow this pattern. Streams are abstract, with a gaggle of concrete implementations for different situations. I don't see what's wrong with that. Now, I've seen inheritance diagrams like the old C++ MFC stuff that were over-the-top complicated. I think they had reasons at the time, but that was then.
I would say that most of the intellectual heavy lift in app development (in my world) is database design, data modeling -- understanding stakeholder requirements and translating them into relational models. I would agree this doesn't really fit an OO paradigm very well, and I don't see that it needs to. For example, I don't think inheritance translates very well in relational terms except in one narrow situation. I usually have base class to define user/timestamp columns like `DateCreated`, `CreatedBy` and so on -- and my model classes (tables) will inherit from that base class in order to get those common properties. But that's really it.
In the app space, it seems like 80% of dev effort goes into building CRUD experiences (forms and list management) of one kind or another. The other 20% is "report creation" of some kind or another, in my world. I don't think there's a perfect distinction between the two, but I would agree there's not really any OO magic in this layer. OO doesn't really make this experience better, IMO. We do have endless battles over UI frameworks and ORM layers. (I'm getting behind Blazor in the web space, and I have my own ORM opinions for sure! Another topic!)
I'm not sure why anyone would challenge the need for abstraction and encapsulation, but there certainly trade-offs and a need for balance. I like this talk (The Wet Codebase by Dan Abramov – Deconstruct[^ on this very topic.
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Hello Charlie,
i have also been working on embedded for some time and always wanted to apply (unsuccessfully) OOP approach to my designs, mostly because of lack of proper tools,in the last years i found python and my point of view has changed.
at this moment i work for a company that makes battery chargers, most of them have been migrated from a totally analog control to a microcontrolled one, there were several embedded programmers involved, each one of them working on his own so you can imagine the kind of mess that exist in software.
founding concepts of OOP you mention are powerful but, like any other tool, you have to choose the one that fits the best to your particular application.
In my case i use a python (a GUI and some scripts on the PC side) to generate C++ code for embedded automatically, and OOP paradigm is the thing that glues all together. here the software changes frequently, and this approach allows those changes to be applied quickly.
using the previous approach to modify an existing application usually takes several days of code reading in order to understand how it works and then apply the required changes.
regards
jdavila
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Practical, pragmatic feedback is that you use what works. Polymorphism and inheritance aren't needed for everything, but they can make some things easier to do. If an application has no polymorphism or explicit inheritance, does that mean it is not object oriented? It depends. Unlike a language where the advanced concepts may not be useful for what you are doing, you can have an object-based application that otherwise follows object-oriented design without polymorphism. Does it matter that you call it object oriented?
Too many software development concepts are treated more like a religion than a tool set to accomplish a goal. I currently work in an application where inheritance is used to an extreme and it works well. I don't even think about it, but I can see how it could be written completely differently without inheritance and still work. I wouldn't want to try though.
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