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I am writing my main manager script for my game. I seems like the script handles 10+ huge if..else..if..else statements. It looks messy and hard to manage. And in monodevelop I am not able to minimise particular parts of code like we can do in eclipse.
I am considering of creating individual script for each part and enable-access-disable it from a common script.
Please direct me to the better ways to do?
In the best case every method or class should have one responsibility, and only one.
Try to extract duplicate code into methods
Try to split up your classes, so that each class does only one thing
Advanced: organize your classes in layers (Model-View-Control) and only talk to other classes through interfaces
share some code structure. it is a good practice to encapsulate blocks of code that perform a particular task into functions that accept parameters,
eg ( myFunction(param1, param2, param3){} )
if you ever have to reuse the code block you merely call the function and have it return the necessary values.
If I have a function (say messUp that does not need to access any private variables of a class (say room), should I write the function inside the class like room.messUp() or outside of it like messUp(room)? It seems the second version reads better to me.
There's a tradeoff involved here. Using a member function lets you:
Override the implementation in derived classes, so that messing up a kitchen could involve trashing the cupboards even if no cupboards are available in a generic room.
Decide that you need to access private variables later on, without having to refactor all the code that uses the function.
Make the function part of an interface, so that a piece of code may require that its argument be mess-up-able.
Using an external function lets you:
Make that function generic, so that you may apply it to rooms, warehouses and oil rigs equally (if they provide the member functions required for messing up).
Keep the class signature small, so that creating mock versions for unit testing (or different implementations) becomes easier.
Change the class implementation without having to examine the code for that function.
There's no real way to have your cake and eat it too, so you have to make choices. A common OO decision is to make everything a method (unless clearly idiotic) and sacrifice the three latter points, but that doesn't mean you should do it in all situations.
Any behaviour of a class of objects should be written as an instance method.
So room.messUp() is the OO way to do this.
Whether messUp has to access any private members of the class or not, is irrelevant, the fact that it's a behaviour of the room, suggests that it's an instance method, as would be cleanUp or paint, etc...
Ignoring which language, I think my first question is if messUp is related to any other functions. If you have a group of related functions, I would tend to stick them in a class.
If they don't access any class variables then you can make them static. This way, they can be called without needing to create an instance of the class.
Beyond that, I would look to the language. In some languages, every function must be a method of some class.
In the end, I don't think it makes a big difference. OOP is simply a way to help organize your application's data and logic. If you embrace it, then you would choose room.messUp() over messUp(room).
i base myself on "C++ Coding Standards: 101 Rules, Guidelines, And Best Practices" by Sutter and Alexandrescu, and also Bob Martin's SOLID. I agree with them on this point of course ;-).
If the message/function doesnt interract so much with your class, you should make it a standard ordinary function taking your class object as argument.
You should not polute your class with behaviours that are not intimately related to it.
This is to repect the Single Responsibility Principle: Your class should remain simple, aiming at the most precise goal.
However, if you think your message/function is intimately related to your object guts, then you should include it as a member function of your class.
Maybe its because I've been coding around two semesters now, but the major stumbling block that I'm having at this point is converting the professor's project description and requirements to actual code. Since I'm currently in Algorithms 101, I basically do a bottom-up process, starting with a blank whiteboard and draw out the object and method interactions, then translate that into classes and code.
But now the prof has tossed interfaces and abstract classes into the mix. Intellectually, I can recognize how they work, but am stubbing my toes figuring out how to use these new tools with the current project (simulating a web server).
In my professors own words, mapping the abstract description to Java code is the real trick. So what steps are best used to go from English (or whatever your language is) to computer code? How do you decide where and when to create an interface, or use an abstract class?
So what steps are best used to go from English (or whatever your language is) to computer code?
Experience is what teaches you how to do this. If it's not coming naturally yet (and don't feel bad if it doesn't, because it takes a long time!), there are some questions you can ask yourself:
What are the main concepts of the system? How are they related to each other? If I was describing this to someone else, what words and phrases would I use? These thoughts will help you decide what classes are useful to think about.
What sorts of behaviors do these things have? Are there natural dependencies between them? (For example, a LineItem isn't relevant or meaningful without the context of an Order, nor is an Engine much use without a Car.) How do the behaviors affect the state of the other objects? Do they communicate with each other, and if so, in what way? These thoughts will help you develop the public interfaces of your classes.
That's just the tip of the iceberg, of course. For more about this thought process in general, see Eric Evans's excellent book, Domain-Driven Design.
How do you decide where and when to create an interface, or use an abstract class?
There's no hard and fast prescriptions; again, experience is the best guide here. That said, there's certainly some rules of thumb you can follow:
If several unrelated or significantly different object types all provide the same kind of functionality, use an interface. For example, if the Steerable interface has a Steer(Vector bearing) method, there may be lots of different things that can be steered: Boats, Airplanes, CargoShips, Cars, et cetera. These are completely unrelated things. But they all share the common interface of being able to be steered.
In general, try to favor an interface instead of an abstract base class. This way you can define a single implementation which implements N interfaces. In the case of Java, you can only have one abstract base class, so you're locked into a particular inheritance hierarchy once you say that a class inherits from another one.
Whenever you don't need implementation from a base class, definitely favor an interface over an abstract base class. This would also be handy if you're operating in a language where inheritance doesn't apply. For example, in C#, you can't have a struct inherit from a base class.
In general...
Read a lot of other people's code. Open source projects are great for that. Respect their licenses though.
You'll never get it perfect. It's an iterative process. Don't be discouraged if you don't get it right.
Practice. Practice. Practice.
Research often. Keep tackling more and more challenging projects / designs. Even if there are easy ones around.
There is no magic bullet, or algorithm for good design.
Nowadays I jump in with a design I believe is decent and work from that.
When the time is right I'll implement understanding the result will have to refactored ( rewritten ) sooner rather than later.
Give this project your best shot, keep an eye out for your mistakes and how things should've been done after you get back your results.
Keep doing this, and you'll be fine.
What you should really do is code from the top-down, not from the bottom-up. Write your main function as clearly and concisely as you can using APIs that you have not yet created as if they already existed. Then, you can implement those APIs in similar fashion, until you have functions that are only a few lines long. If you code from the bottom-up, you will likely create a whole lot of stuff that you don't actually need.
In terms of when to create an interface... pretty much everything should be an interface. When you use APIs that don't yet exist, assume that every concrete class is an implementation of some interface, and use a declared type that is indicative of that interface. Your inheritance should be done solely with interfaces. Only create concrete classes at the very bottom when you are providing an implementation. I would suggest avoiding abstract classes and just using delegation, although abstract classes are also reasonable when two different implementations differ only slightly and have several functions that have a common implementation. For example, if your interface allows one to iterate over elements and also provides a sum function, the sum function is a trivial to implement in terms of the iteration function, so that would be a reasonable use of an abstract class. An alternative would be to use the decorator pattern in that case.
You might also find the Google Techtalk "How to Design a Good API and Why it Matters" to be helpful in this regard. You might also be interested in reading some of my own software design observations.
Also, for the coming future, you can keep in pipeline to read the basics on domain driven design to align yourself to the real world scenarios - it gives a solid foundation for requirements mapping to the real classes.
All,
Wanted to get a few thoughts on this. Lately I am becoming more and more of a subscriber of "purist" DI/IOC principles when designing/developing. Part of this (a big part) involves making sure there is little coupling between my classes, and that their dependencies are resolved via the constructor (there are certainly other ways of managing this, but you get the idea).
My basic premise is that extension methods violate the principles of DI/IOC.
I created the following extension method that I use to ensure that the strings inserted into database tables are truncated to the right size:
public static class StringExtensions
{
public static string TruncateToSize(this string input, int maxLength)
{
int lengthToUse = maxLength;
if (input.Length < maxLength)
{
lengthToUse = input.Length;
}
return input.Substring(0, lengthToUse);
}
}
I can then call my string from within another class like so:
string myString = "myValue.TruncateThisPartPlease.";
myString.TruncateToSize(8);
A fair translation of this without using an extension method would be:
string myString = "myValue.TruncateThisPartPlease.";
StaticStringUtil.TruncateToSize(myString, 8);
Any class that uses either of the above examples could not be tested independently of the class that contains the TruncateToSize method (TypeMock aside). If I were not using an extension method, and I did not want to create a static dependency, it would look more like:
string myString = "myValue.TruncateThisPartPlease.";
_stringUtil.TruncateToSize(myString, 8);
In the last example, the _stringUtil dependency would be resolved via the constructor and the class could be tested with no dependency on the actual TruncateToSize method's class (it could be easily mocked).
From my perspective, the first two examples rely on static dependencies (one explicit, one hidden), while the second inverts the dependency and provides reduced coupling and better testability.
So does the use of extension methods conflict with DI/IOC principles? If you're a subscriber of IOC methodology, do you avoid using extension methods?
I think it's fine - because it's not like TruncateToSize is a realistically replaceable component. It's a method which will only ever need to do a single thing.
You don't need to be able to mock out everything - just services which either disrupt unit testing (file access etc) or ones which you want to test in terms of genuine dependencies. If you were using it to perform authentication or something like that, it would be a very different matter... but just doing a straight string operation which has absolutely no configurability, different implementation options etc - there's no point in viewing that as a dependency in the normal sense.
To put it another way: if TruncateToSize were a genuine member of String, would you even think twice about using it? Do you try to mock out integer arithmetic as well, introducing IInt32Adder etc? Of course not. This is just the same, it's only that you happen to be supplying the implementation. Unit test the heck out of TruncateToSize and don't worry about it.
I see where you are coming from, however, if you are trying to mock out the functionality of an extension method, I believe you are using them incorrectly. Extension methods should be used to perform a task that would simply be inconvenient syntactically without them. Your TruncateToLength is a good example.
Testing TruncateToLength would not involve mocking it out, it would simply involve the creation of a few strings and testing that the method actually returned the proper value.
On the other hand, if you have code in your data layer contained in extension methods that is accessing your data store, then yes, you have a problem and testing is going to become an issue.
I typically only use extension methods in order to provide syntactic sugar for small, simple operations.
Extension methods, partial classes and dynamic objects. I really like them, however you must tread carefully , there be monsters here.
I would take a look at dynamic languages and see how they cope with these sort of problems on a day to day basis, its really enlightening. Especially when they have nothing to stop them from doing stupid things apart from good design and discipline. Everything is dynamic at run time, the only thing to stop them is the computer throwing a major run time error. "Duck Typing" is the maddest thing I have ever seen, good code is down to good program design, respect for others in your team, and the trust that every member, although have the ability to do some wacky things choose not to because good design leads to better results.
As for your test scenario with mock objects/ICO/DI, would you really put some heavy duty work in an extension method or just some simple static stuff that operate in a functional type way? I tend to use them like you would in a functional programming style, input goes in, results come out with no magic in the middle, just straight up framework classes that you know the guys at MS have designed and tested :P that you can rely on.
If your are doing some heavy lifting stuff using extension methods I would look at your program design again, check out your CRC designs, Class models, Use Cases, DFD's, action diagrams or whatever you like to use and figure out where in this design you planned to put this stuff in an extension method instead of a proper class.
At the end of the day, you can only test against your system design and not code outside of your scope. If you going to use extension classes, my advice would be to look at Object Composition models instead and use inheritance only when there is a very good reason.
Object Composition always wins out with me as they produce solid code. You can plug them in, take them out and do what you like with them. Mind you this all depends on whether you use Interfaces or not as part of your design. Also if you use Composition classes, the class hierarchy tree gets flattened into discrete classes and there are fewer places where your extension method will be picked up through inherited classes.
If you must use a class that acts upon another class as is the case with extension methods, look at the visitor pattern first and decide if its a better route.
Its a pain because they are hard to mock. I usually use one of these strategies
Yep, scrap the extension its a PITA to mock out
Use the extension and just test that it did the right thing. i.e. pass data into the truncate and check it got truncated
If it's not some trivial thing, and I HAVE to mock it, I'll make my extension class have a setter for the service it uses, and set that in the test code.
i.e.
static class TruncateExtensions{
public ITruncateService Service {private get;set;}
public string TruncateToSize(string s, int size)
{
return (Service ?? Service = new MyDefaultTranslationServiceImpl()). TruncateToSize(s, size);
}
}
This is a bit scary because someone might set the service when they shouldn't, but I'm a little cavalier sometimes, and if it was really important, I could do something clever with #if TEST flags, or the ServiceLocator pattern to avoid the setter being used in production.
Currently I am making some decisions for my first objective-c API. Nothing big, just a little help for myself to get things done faster in the future.
After reading a few hours about different patterns like making categories, singletons, and so on, I came accross something that I like because it seems easy to maintain for me. I'm making a set of useful functions, that can be useful everywhere.
So what I did is:
1) I created two new files (.h, .m), and gave the "class" a name: SLUtilsMath, SLUtilsGraphics, SLUtilsSound, and so on. I think of that as kind of "namespace", so all those things will always be called SLUtils******. I added all of them into a Group SL, which contains a subgroup SLUtils.
2) Then I just put my functions signatures in the .h file, and the implementations of the functions in the .m file. And guess what: It works!! I'm happy with it, and it's easy to use. The only nasty thing about it is, that I have to include the appropriate header every time I need it. But that's okay, since that's normal. I could include it in the header prefix pch file, though.
But then, I went to toilet and a ghost came out there, saying: "Hey! Isn't it better to make real methods, instead of functions? Shouldn't you make class methods, so that you have to call a method rather than a function? Isn't that much cooler and doesn't it have a better performance?" Well, for readability I prefer the functions. On the other hand they don't have this kind of "named parameters" like methods, a.f.a.i.k..
So what would you prefer in that case?
Of course I dont want to allocate an object before using a useful method or function. That would be harrying.
Maybe the toilet ghost was right. There IS a cooler way. Well, for me, personally, this is great:
MYNAMESPACECoolMath.h
#import <Foundation/Foundation.h>
#interface MYNAMESPACECoolMath : NSObject {
}
+ (float)randomizeValue:(float)value byPercent:(float)percent;
+ (float)calculateHorizontalGravity:(CGPoint)p1 andPoint:(CGPoint)p2;
// and some more
#end
Then in code, I would just import that MYNAMESPACECoolMath.h and just call:
CGFloat myValue = [MYNAMESPACECoolMath randomizeValue:10.0f byPercent:5.0f];
with no nasty instantiation, initialization, allocation, what ever. For me that pattern looks like a static method in java, which is pretty nice and easy to use.
The advantage over a function, is, as far as I noticed, the better readability in code. When looking at a CGRectMake(10.0f, 42.5f, 44.2f, 99.11f) you'll may have to look up what those parameters stand for, if you're not so familiar with it. But when you have a method call with "named" parameters, then you see immediately what the parameter is.
I think I missed the point what makes a big difference to a singleton class when it comes to simple useful methods / functions that can be needed everywhere. Making special kind of random values don't belong to anything, it's global. Like grass. Like trees. Like air. Everyone needs it.
Performance-wise, a static method in a static class compile to almost the same thing as a function.
Any real performance hits you'd incur would be in object instantiation, which you said you'd want to avoid, so that should not be an issue.
As far as preference or readability, there is a trend to use static methods more than necessary because people are viewing Obj-C is an "OO-only" language, like Java or C#. In that paradigm, (almost) everything must belong to a class, so class methods are the norm. In fact, they may even call them functions. The two terms are interchangeable there. However, this is purely convention. Convention may even be too strong of a word. There is absolutely nothing wrong with using functions in their place and it is probably more appropriate if there are no class members (even static ones) that are needed to assist in the processing of those methods/functions.
The problem with your approach is the "util" nature of it. Almost anything with the word "util" it in suggests that you have created a dumping ground for things you don't know where to fit into your object model. That probably means that your object model is not in alignment with your problem space.
Rather than working out how to package up utility functions, you should be thinking about what model objects these functions should be acting upon and then put them on those classes (creating the classes if needed).
To Josh's point, while there is nothing wrong with functions in ObjC, it is a very strongly object-oriented language, based directly on the grand-daddy of object-oriented languages, Smalltalk. You should not abandon the OOP patterns lightly; they are the heart of Cocoa.
I create private helper functions all the time, and I create public convenience functions for some objects (NSLocalizedString() is a good example of this). But if you're creating public utility functions that aren't front-ends to methods, you should be rethinking your patterns. And the first warning sign is the desire to put the word "util" in a file name.
EDIT
Based on the particular methods you added to your question, what you should be looking at are Categories. For instance, +randomizeValue:byPercent: is a perfectly good NSNumber category:
// NSNumber+SLExtensions.h
- (double)randomizeByPercent:(CGFloat)percent;
+ (double)randomDoubleNear:(CGFloat)percent byPercent:(double)number;
+ (NSNumber *)randomNumberNear:(CGFloat)percent byPercent:(double)number;
// Some other file that wants to use this
#import "NSNumber+SLExtensions.h"
randomDouble = [aNumber randomizeByPercent:5.0];
randomDouble = [NSNumber randomDoubleNear:5.0 byPercent:7.0];
If you get a lot of these, then you may want to split them up into categories like NSNumber+Random. Doing it with Categories makes it transparently part of the existing object model, though, rather than creating classes whose only purpose is to work on other objects.
You can use a singleton instance instead if you want to avoid instantiating a bunch of utility objects.
There's nothing wrong with using plain C functions, though. Just know that you won't be able to pass them around using #selector for things like performSelectorOnMainThread.
When it comes to performance of methods vs. functions, Mike Ash has some great numbers in his post "Performance Comparisons of Common Operations". Objective-C message send operations are extremely fast, so much so that you'd have to have a really tight computational loop to even see the difference. I think that using functions vs. methods in your approach will come down to the stylistic design issues that others have described.
Optimise the system, not the function calls.
Implement what is easiest to understand and then when the whole system works, profile it and speed up what's slow. I doubt very much that the objective-c runtime overhead of a static class is going to matter one bit to your whole app.