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• How to name an subclass that add a minor, detailed thing?

  - by Louis Rhys

  What is the most concise (yet descriptive) way of naming a subclass that only add a specific minor thing to the parent? I encountered this case a lot in WPF, where sometime I have to add a small functionality to an out-of-the-box control for specific cases. Example: TreeView doesn't change the SelectedItem on right-click, but I have to make one that does in my application. Some possible names are TreeViewThatChangesSelectedItemOnRightClick (way too wordy and maybe difficult to read because there is so many words concantenated together) TreeView_SelectedItemChangesOnRightClick (slightly more readable, but still too wordy and the underscore also breaks the normal convention for class names) TreeViewThatChangesSIOnRC (non-obvious acronym), ExtendedTreeView (more concise, but doesn't describe what it is doing. Besides, I already found a class called this in the library, that I don't want to use/modify in my application). LouisTreeView, MyTreeView, etc. (doesn't describe what it is doing). It seems that I can't find a name which sounds right. What do you do in situation like this?

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• Exporting XNA class library as a DLL file

  - by Will Bagley

  I have downloaded an open source project that I intend to use with my current game. The download came with all the class files from the original project as well as a pre-compiled DLL file representing the project. I was able to easily link this DLL with my current project and get it working just fine, no problems there. The problem I now have is that I want to make a couple of changes to the original libraries (extend its functionality a bit to better suit my needs) and re-export the class library as a DLL again, but I have no clue how to do this. Is there some simple way in VS where I can just take the class library and export/compile it as a DLL file again or is there more to it than that? This seems like something that should be pretty simple but my efforts to find an answer have so far come up with nothing. Thanks in advance.

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• UML Class diagrams with Java packages?

  - by loosebruce

  I am trying to model in UML 2.0 a Java servlet application that has three classes Servlet class; essentially a main class that acts as the controller DatabaseLogic; contains methods for database operations XMLBuilder; builds an XML from a query result string The classes use a variety of packages from the Java library. I am unsure how to model this in UML Do I have to create a package and show which libraries are used for each individual class or can I just have one large package in the diagram with all the libraries showing which classes have dependencies on which. As per this diagram This is my first time working with java properly (im a C++ guy) Apart from being a bit messy , is this a correct UML representation of the system I described? Does a Package in UML mean the same as a Package in Java?

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• Torque2D, Class vs Datablock

  - by Max Kielland

  I'm scripting my first game with Torque2D and have not fully understood the difference between "Class" and Datablock. To me it seems like Datablock is similar to a struct in C/C++ or a Record in Pascal. If I create Datablocks with new, are they instantiated in the same way as a "Class"? I have a large TileMap and need to attach some information to each Tile. I was thinking to use a Datablock, as a struct, to attach this information to the tile's CustomData property. The two questions are: What is a Datablock and should I use a Datablock or a "Class" for this tile information?

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• XNA Moddable Game - Architecture Design and Reflection

  - by David K

  I've decided to embark on an XNA moddable game project of a simple rogue style. For all purposes of this question, I'm going to not be using a scripting engine, but rather allow modders to directly compile assemblies that are loaded by the game at run time. I know about the security problems this may raise. So in order to expose the moddable content, I have gone about creating a generic project in XNA called MyModel. This contains a number of interfaces that all inherit from IPlugin, such as IGameSystem, IRenderingSystem, IHud, IInputSystem etc. Then I've created another project called MyRogueModel. This references MyModel project, and holds interfaces such as IMonster, IPlayer, IDungeonGenerator, IInventorySystem. More rogue specific interfaces, but again, all interfaces in this project inherit from IPlugin. Then finally, I've created another project called MyRogueGame, that references both MyModel and MyRogueModel projects. This project will be the game that you run and play. Here I have put the actual implementation of the Monster, DungeonGenerator, InputSystem and RenderingSystem classes. This project will also scan the mods directory during run time and load any IPlugins it finds using reflection and override anything it finds from the default. For example if it finds a new implementation of the DungeonGenerator it will use that one instead. Now my question is, in order to get this far, I have effectively 2 projects that contain nothing but interfaces... which seems a little... strange ? For people to create mods for the game, I would give them both the MyModel and MyRogueModel assemblies in which they would reference. I'm not sure whether this is the right way to do it, but my reasoning goes as follows : If I write 1 input system, I can use it in any game I write. If I create 3 rogue like games, and a modder writes 1 rendering system, that modder could use the rendering system for all 3 games, because it all comes from the MyModel project. I come from a more web based C# role, so having empty interface projects doesn't seem wrong, its just something I haven't done before. Before I embark on something that might be crazy, I'd just like to know whether this is a foolish idea and whether there's a better (or established) design principle I should be following ?

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• Is it evil to model JSON responses to classes when they are mostly smilar?

  - by Aybe

  Here's the problem : While implementing a C# wrapper for an online API (Discogs) I've been faced to a dilemma : quite often the responses returned have mostly similar members and while modeling these responses to classes, some questions surfaces on which way to go would be the best. Example : Querying for a 'release' or a 'master' will return an object that contains an array of 'artist', however these 'artists' do not exactly have the same members. Currently I decided to represent these 'artists' as a single 'Artist' class, against having respective 'ReleaseArtist' and 'MasterArtist' classes which soon becomes very confusing even though another problem arises : when a category (master or release) does not return these members, they will be null. Though it might sound confusing as well I find it less confusing than the former situation as I've tackled the problem by simply not showing null members when visualizing these objects. Is this the right approach to follow ? An example of these differences : public class Artist { public List<Alias> Aliases { get; set; } public string DataQuality { get; set; } public List<Image> Images { get; set; } public string Name { get; set; } public List<string> NameVariations { get; set; } public string Profile { get; set; } public string Realname { get; set; } public string ReleasesUrl { get; set; } public string ResourceUrl { get; set; } public string Uri { get; set; } public List<string> Urls { get; set; } } public class ReleaseArtist { public string Join { get; set; } public string Name { get; set; } public string Anv { get; set; } public string Tracks { get; set; } public string Role { get; set; } public string ResourceUrl { get; set; } public int Id { get; set; } }

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• Game Code Design for Rendering

  - by kuroutadori

  I first created a game on the iPhone and I'm now porting it to Android. I wrote most of the code in C++, but when it came to porting it wasn't so easy. The Android way is to have two threads, one for rendering and one for updating. This due to some devices blocking when updating the hardware. My problem is that I am coming from the iPhone. When I transition, say from the Menu to the Game, I would stop the Animation (Rendering) and load up the next Manager (the Menu has a Manager and so has the Game). I could implement the same thing on Android, but I have noticed on game ports like Quake, don't do this - as far as I can tell. I have learnt that I cannot just dynamically add another Renderer class the the tree because I will probably get a dequeuing buffer error - which I believe to be a problem with the OpenGL ES side. So how is it done?

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• UI Design Patterns : Are you developing a Fusion Apps extension, an ADF or Webcenter App?

  - by asantaga

  A big question I get asked when speaking to partners who are developing Oracle ADF, or Webcenter, Apps is how to make it look nice.. Some of the big SIs ask me, "Do we have any design patterns/guidelines we can use?". .. Alas website design is a very personal thing and each website will have different requirements and needs, however I am now pleased to say we've just launched "Oracle Fusion Applications Design Patterns" website.   The website is the result of many years of Oracle R&D into user interface design for Fusion applications and features a really cool web app which allows you to visualise the UI components in action. Although many of the design patterns are related to ADF , its worth noting that ADF took its lead from Oracle Fusion Applications User Interface needs - not the other way around, its just taken us a while to publish these. Coupled together with the dashboard patterns this makes are really cool extra asset for your kit bag Design Patterns Oracle dashboard patterns and guidelines Usable Apps.oracle.com Enjoy

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• Why should a class be anything other than "abstract" or "final/sealed"

  - by Nicolas Repiquet

  After 10+ years of java/c# programming, I find myself creating either: abstract classes: contract not meant to be instantiated as-is. final/sealed classes: implementation not meant to serve as base class to something else. I can't think of any situation where a simple "class" (i.e. neither abstract nor final/sealed) would be "wise programming". Why should a class be anything other than "abstract" or "final/sealed" ? EDIT This great article explains my concerns far better than I can.

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• Functions returning pointers

  - by fg nu

  C++ noob here. I have a very basic question about a construct I found in the C++ book I am reading. // class declaration class CStr { char sData[256]; public: char* get(void); }; // implementation of the function char* CStr::get(void) { return sData; } So the Cstr::get function is obviously meant to return a character pointer, but the function is passing what looks like the value (return sData). Does C++ know to return the address of the returned object? My guess would have been that the function definition would be return &sData.

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• How to ensure that a member variable is initialized before calling a class method

  - by Omkar Ekbote

  There's a class with a parametrized constructor that initializes a member variable. All public methods of the class then use this member variable to do something. I want to ensure that the caller always creates an object using the parametrized constructor (there is also a setter for this member variable) and then call that object's methods. In essence, it should be impossible for the caller to call any method without setting a value to the member variable (either by using the parametrized constructor or the setter). Currently, a caller can simply make an object using the default constructor and then call that object's method - I want to avoid checking whether or not the member variable is set in each and every one of the 20-odd methods of the class (and throw an exception if it is not). Though a runtime solution is acceptable (better than the one I mentioned above); a compile-time solution is preferable so that any developer will not be allowed to make that mistake and then waste hours debuggging it!

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• Why is it good to split a program into multiple classes?

  - by user1276078

  I'm still a student in high school (entering 10th grade), and I have yet to take an actual computer course in school. Everything I've done so far is through books. Those books have taught me concepts such as inheritance, but how does splitting a program into multiple classes help? The books never told me. I'm asking this mainly because of a recent project. It's an arcade video game, sort of like a flash game as some people have said (although I have no idea what a flash game is). The thing is, it's only one class. It works perfectly fine (a little occasional lag however) with just one class. So, I'm just asking how splitting it into multiple classes would help it. This project was in JAVA and I am the only person working on it, for the record.

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• Should Equality be commutative within a Class Hierachy?

  - by vossad01

  It is easy to define the Equals operation in ways that are not commutative. When providing equality against other types, there are obviously situations (in most languages) were equality not being commutative is unavoidable. However, within one's own inheritance hierarchy where the root base class defines an equality member, a programmer has more control. Thus you can create situations where (A = B) ? (B = A), where A and B both derive from base class T Substituting the = with the appropriate variation for a given language. (.Equals(_), ==, etc.) That seems wrong to me, however, I recognize I may be biased by background in Mathematics. I have not been in programming long enough to know what is standard/accepted/preferred practice when programming. Do most programmers just accept .Equals(_)may not be commutative and code defensibly. Do they expect commutativity and get annoyed if it is not. In short, when working in a class hierarchy, should effort me made to ensure Equality is commutative?

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• PHP OOP Design Patterns: Should I Create two seperate classes for registration and form validation?

  - by Joshua Poshua

  So here's my problem: I have two types of registration, registration A and registration B, each will have some of the same fields and some different fields. I was going to create abstract class registration and both A and B would have their own classes that extend from registration. My question is, should I create a seperate Validation class with seperate A and B validation classes that extend? or is there a better pattern to use for something like this? Thanks

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• Designing status management for a file processing module

  - by bot

  The background One of the functionality of a product that I am currently working on is to process a set of compressed files ( containing XML files ) that will be made available at a fixed location periodically (local or remote location - doesn't really matter for now) and dump the contents of each XML file in a database. I have taken care of the design for a generic parsing module that should be able to accommodate the parsing of any file type as I have explained in my question linked below. There is no need to take a look at the following link to answer my question but it would definitely provide a better context to the problem Generic file parser design in Java using the Strategy pattern The Goal I want to be able to keep a track of the status of each XML file and the status of each compressed file containing the XML files. I can probably have different statuses defined for the XML files such as NEW, PROCESSING, LOADING, COMPLETE or FAILED. I can derive the status of a compressed file based on the status of the XML files within the compressed file. e.g status of the compressed file is COMPLETE if no XML file inside the compressed file is in a FAILED state or status of the compressed file is FAILED if the status of at-least one XML file inside the compressed file is FAILED. A possible solution The Model I need to maintain the status of each XML file and the compressed file. I will have to define some POJOs for holding the information about an XML file as shown below. Note that there is no need to store the status of a compressed file as the status of a compressed file can be derived from the status of its XML files. public class FileInformation { private String compressedFileName; private String xmlFileName; private long lastModifiedDate; private int status; public FileInformation(final String compressedFileName, final String xmlFileName, final long lastModified, final int status) { this.compressedFileName = compressedFileName; this.xmlFileName = xmlFileName; this.lastModifiedDate = lastModified; this.status = status; } } I can then have a class called StatusManager that aggregates a Map of FileInformation instances and provides me the status of a given file at any given time in the lifetime of the appliciation as shown below : public class StatusManager { private Map<String,FileInformation> processingMap = new HashMap<String,FileInformation>(); public void add(FileInformation fileInformation) { fileInformation.setStatus(0); // 0 will indicates that the file is in NEW state. 1 will indicate that the file is in process and so on.. processingMap.put(fileInformation.getXmlFileName(),fileInformation); } public void update(String filename,int status) { FileInformation fileInformation = processingMap.get(filename); fileInformation.setStatus(status); } } That takes care of the model for the sake of explanation. So whats my question? Edited after comments from Loki and answer from Eric : - I would like to know if there are any existing design patterns that I can refer to while coming up with a design. I would also like to know how I should go about designing the status management classes. I am more interested in understanding how I can model the status management classes. I am not interested in how other components are going to be updated about a change in status at the moment as suggested by Eric.

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• How should I plan the inheritance structure for my game?

  - by Eric Thoma

  I am trying to write a platform shooter in C++ with a really good class structure for robustness. The game itself is secondary; it is the learning process of writing it that is primary. I am implementing an inheritance tree for all of the objects in my game, but I find myself unsure on some decisions. One specific issue that it bugging me is this: I have an Actor that is simply defined as anything in the game world. Under Actor is Character. Both of these classes are abstract. Under Character is the Philosopher, who is the main character that the user commands. Also under Character is NPC, which uses an AI module with stock routines for friendly, enemy and (maybe) neutral alignments. So under NPC I want to have three subclasses: FriendlyNPC, EnemyNPC and NeutralNPC. These classes are not abstract, and will often be subclassed in order to make different types of NPC's, like Engineer, Scientist and the most evil Programmer. Still, if I want to implement a generic NPC named Kevin, it would nice to be able to put him in without making a new class for him. I could just instantiate a FriendlyNPC and pass some values for the AI machine and for the dialogue; that would be ideal. But what if Kevin is the one benevolent Programmer in the whole world? Now we must make a class for him (but what should it be called?). Now we have a character that should inherit from Programmer (as Kevin has all the same abilities but just uses the friendly AI functions) but also should inherit from FriendlyNPC. Programmer and FriendlyNPC branched away from each other on the inheritance tree, so inheriting from both of them would have conflicts, because some of the same functions have been implemented in different ways on the two of them. 1) Is there a better way to order these classes to avoid these conflicts? Having three subclasses; Friendly, Enemy and Neutral; from each type of NPC; Engineer, Scientist, and Programmer; would amount to a huge number of classes. I would share specific implementation details, but I am writing the game slowly, piece by piece, and so I haven't implemented past Character yet. 2) Is there a place where I can learn these programming paradigms? I am already trying to take advantage of some good design patterns, like MVC architecture and Mediator objects. The whole point of this project is to write something in good style. It is difficult to tell what should become a subclass and what should become a state (i.e. Friendly boolean v. Friendly class). Having many states slows down code with if statements and makes classes long and unwieldy. On the other hand, having a class for everything isn't practical. 3) Are there good rules of thumb or resources to learn more about this? 4) Finally, where does templating come in to this? How should I coordinate templates into my class structure? I have never actually taken advantage of templating honestly, but I hear that it increases modularity, which means good code.

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• How to safely copy an object?

  - by Prog

  This question is going to be a little long. Please bear with me. Something that happened in a project of mine made me think about how to safely copy objects. I'll present the situation I had and then ask a question. There was a class SomeClass: class SomeClass{ Thing[] things; public SomeClass(Thing[] things){ this.things = things; } // irrelevant stuff omitted public SomeClass copy(){ return new SomeClass(things); } } There was another class Processor that takes SomeClass objects, copies them (via someClassInstance.copy()), manipulates the copy's state, and returns the copy. Here it is: class Processor{ public SomeClass processObject(SomeClass object){ SomeClass copy = object.copy(); manipulateTheCopy(copy); return copy; } // irrelevant stuff omitted } I ran this, and it had bugs. I looked into these bugs, and it turned out that the manipulations Processor does on copy actually affect not only the copy, but also the original SomeClass object that was passed into processObject. I found out that it was because the original and the copy shared state - because the original passed it's field things into the copy when creating it. This made me realize that copying objects is harder than simply instantiating them with the same fields as the original. For the two objects to be completely disconnected, without any shared state, each of the fields passed to the copy also has to be copied. And if that object contains other objects - they have to be copied too. And so on. So basically, in order to be able to actually copy an object, each class in the system must have a copy() method, that also invokes copy() on all of it's fields, and so on. So for example, for copy() in SomeClass to work, it needs to look like this: public SomeClass copy(){ Thing[] copyThings = new Thing[things.length]; for(int i=0; i<things.length; i++) copyThings[i] = things[i].copy(); return new SomeClass(copyThings); } And if Thing has object fields of it's own, than it's own copy() method must be appropriate: class Thing{ Apple apple; Pencil pencil; int number; public Thing(Apple apple, Pencil pencil, int number){ this.apple = apple; this.pencil = pencil; this.number = number; } public Thing copy(){ // 'number' is a primitve. return new Thing(apple.getCopy(), pencil.getCopy(), number); } } And so on. Of course, instead of all classes having a copy() method, the copying mechanism can happen in all of the getters and the constructors of classes (unless places where it isn't suitable, for example when the field points to an external object, not to an object that 'is part' of this object). Still, that means that in order to be able to safely copy an object - most classes would have to have copying mechanisms in their getters. My question is divided into two parts: How frequently do you need to get a copy of an object? Is this a regular issue? Is the technique described common and/or reasonable? Or is there a better way to make safe copies of objects? Or is there an easier way to safely copy objects, without them sharing any state?

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• Patterns for a tree of persistent data with multiple storage options?

  - by Robin Winslow

  I have a real-world problem which I'll try to abstract into an illustrative example. So imagine I have data objects in a tree, where parent objects can access children, and children can access parents: // Interfaces interface IParent<TChild> { List<TChild> Children; } interface IChild<TParent> { TParent Parent; } // Classes class Top : IParent<Middle> {} class Middle : IParent<Bottom>, IChild<Top> {} class Bottom : IChild<Middle> {} // Usage var top = new Top(); var middles = top.Children; // List<Middle> foreach (var middle in middles) { var bottoms = middle.Children; // List<Bottom> foreach (var bottom in bottoms) { var middle = bottom.Parent; // Access the parent var top = middle.Parent; // Access the grandparent } } All three data objects have properties that are persisted in two data stores (e.g. a database and a web service), and they need to reflect and synchronise with the stores. Some objects only request from the web service, some only write to it. Data Mapper My favourite pattern for data access is Data Mapper, because it completely separates the data objects themselves from the communication with the data store: class TopMapper { public Top FetchById(int id) { var top = new Top(DataStore.TopDataById(id)); top.Children = MiddleMapper.FetchForTop(Top); return Top; } } class MiddleMapper { public Middle FetchById(int id) { var middle = new Middle(DataStore.MiddleDataById(id)); middle.Parent = TopMapper.FetchForMiddle(middle); middle.Children = BottomMapper.FetchForMiddle(bottom); return middle; } } This way I can have one mapper per data store, and build the object from the mapper I want, and then save it back using the mapper I want. There is a circular reference here, but I guess that's not a problem because most languages can just store memory references to the objects, so there won't actually be infinite data. The problem with this is that every time I want to construct a new Top, Middle or Bottom, it needs to build the entire object tree within that object's Parent or Children property, with all the data store requests and memory usage that that entails. And in real life my tree is much bigger than the one represented here, so that's a problem. Requests in the object In this the objects request their Parents and Children themselves: class Middle { private List<Bottom> _children = null; // cache public List<Bottom> Children { get { _children = _children ?? BottomMapper.FetchForMiddle(this); return _children; } set { BottomMapper.UpdateForMiddle(this, value); _children = value; } } } I think this is an example of the repository pattern. Is that correct? This solution seems neat - the data only gets requested from the data store when you need it, and thereafter it's stored in the object if you want to request it again, avoiding a further request. However, I have two different data sources. There's a database, but there's also a web service, and I need to be able to create an object from the web service and save it back to the database and then request it again from the database and update the web service. This also makes me uneasy because the data objects themselves are no longer ignorant of the data source. We've introduced a new dependency, not to mention a circular dependency, making it harder to test. And the objects now mask their communication with the database. Other solutions Are there any other solutions which could take care of the multiple stores problem but also mean that I don't need to build / request all the data every time?

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• Too complex/too many objects?

  - by Mike Fairhurst

  I know that this will be a difficult question to answer without context, but hopefully there are at least some good guidelines to share on this. The questions are at the bottom if you want to skip the details. Most are about OOP in general. Begin context. I am a jr dev on a PHP application, and in general the devs I work with consider themselves to use many more OO concepts than most PHP devs. Still, in my research on clean code I have read about so many ways of using OO features to make code flexible, powerful, expressive, testable, etc. that is just plain not in use here. The current strongly OO API that I've proposed is being called too complex, even though it is trivial to implement. The problem I'm solving is that our permission checks are done via a message object (my API, they wanted to use arrays of constants) and the message object does not hold the validation object accountable for checking all provided data. Metaphorically, if your perm containing 'allowable' and 'rare but disallowed' is sent into a validator, the validator may not know to look for 'rare but disallowed', but approve 'allowable', which will actually approve the whole perm check. We have like 11 validators, too many to easily track at such minute detail. So I proposed an AtomicPermission class. To fix the previous example, the perm would instead contain two atomic permissions, one wrapping 'allowable' and the other wrapping 'rare but disallowed'. Where previously the validator would say 'the check is OK because it contains allowable,' now it would instead say '"allowable" is ok', at which point the check ends...and the check fails, because 'rare but disallowed' was not specifically okay-ed. The implementation is just 4 trivial objects, and rewriting a 10 line function into a 15 line function. abstract class PermissionAtom { public function allow(); // maybe deny() as well public function wasAllowed(); } class PermissionField extends PermissionAtom { public function getName(); public function getValue(); } class PermissionIdentifier extends PermissionAtom { public function getIdentifier(); } class PermissionAction extends PermissionAtom { public function getType(); } They say that this is 'not going to get us anything important' and it is 'too complex' and 'will be difficult for new developers to pick up.' I respectfully disagree, and there I end my context to begin the broader questions. So the question is about my OOP, are there any guidelines I should know: is this too complicated/too much OOP? Not that I expect to get more than 'it depends, I'd have to see if...' when is OO abstraction too much? when is OO abstraction too little? how can I determine when I am overthinking a problem vs fixing one? how can I determine when I am adding bad code to a bad project? how can I pitch these APIs? I feel the other devs would just rather say 'its too complicated' than ask 'can you explain it?' whenever I suggest a new class.

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• How to design a C / C++ library to be usable in many client languages?

  - by Brian Schimmel

  I'm planning to code a library that should be usable by a large number of people in on a wide spectrum of platforms. What do I have to consider to design it right? To make this questions more specific, there are four "subquestions" at the end. Choice of language Considering all the known requirements and details, I concluded that a library written in C or C++ was the way to go. I think the primary usage of my library will be in programs written in C, C++ and Java SE, but I can also think of reasons to use it from Java ME, PHP, .NET, Objective C, Python, Ruby, bash scrips, etc... Maybe I cannot target all of them, but if it's possible, I'll do it. Requirements It would be to much to describe the full purpose of my library here, but there are some aspects that might be important to this question: The library itself will start out small, but definitely will grow to enormous complexity, so it is not an option to maintain several versions in parallel. Most of the complexity will be hidden inside the library, though The library will construct an object graph that is used heavily inside. Some clients of the library will only be interested in specific attributes of specific objects, while other clients must traverse the object graph in some way Clients may change the objects, and the library must be notified thereof The library may change the objects, and the client must be notified thereof, if it already has a handle to that object The library must be multi-threaded, because it will maintain network connections to several other hosts While some requests to the library may be handled synchronously, many of them will take too long and must be processed in the background, and notify the client on success (or failure) Of course, answers are welcome no matter if they address my specific requirements, or if they answer the question in a general way that matters to a wider audience! My assumptions, so far So here are some of my assumptions and conclusions, which I gathered in the past months: Internally I can use whatever I want, e.g. C++ with operator overloading, multiple inheritance, template meta programming... as long as there is a portable compiler which handles it (think of gcc / g++) But my interface has to be a clean C interface that does not involve name mangling Also, I think my interface should only consist of functions, with basic/primitive data types (and maybe pointers) passed as parameters and return values If I use pointers, I think I should only use them to pass them back to the library, not to operate directly on the referenced memory For usage in a C++ application, I might also offer an object oriented interface (Which is also prone to name mangling, so the App must either use the same compiler, or include the library in source form) Is this also true for usage in C# ? For usage in Java SE / Java EE, the Java native interface (JNI) applies. I have some basic knowledge about it, but I should definitely double check it. Not all client languages handle multithreading well, so there should be a single thread talking to the client For usage on Java ME, there is no such thing as JNI, but I might go with Nested VM For usage in Bash scripts, there must be an executable with a command line interface For the other client languages, I have no idea For most client languages, it would be nice to have kind of an adapter interface written in that language. I think there are tools to automatically generate this for Java and some others For object oriented languages, it might be possible to create an object oriented adapter which hides the fact that the interface to the library is function based - but I don't know if its worth the effort Possible subquestions is this possible with manageable effort, or is it just too much portability? are there any good books / websites about this kind of design criteria? are any of my assumptions wrong? which open source libraries are worth studying to learn from their design / interface / souce? meta: This question is rather long, do you see any way to split it into several smaller ones? (If you reply to this, do it as a comment, not as an answer)

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• Graphics module: Am I going the right way?

  - by Paul

  I'm trying to write the graphics module of my engine. That is, this part of the code only provides an interface through which to load images, fonts, etc and draw them on the screen. It is also a wrapper for the library I'm using (SDL in this case). Here are the interfaces for my Image, Font and GraphicsRenderer classes. Please tell me if I'm going the right way. Image class Image { public: Image(); Image(const Image& other); Image(const char* file); ~Image(); bool load(const char* file); void free(); bool isLoaded() const; Image& operator=(const Image& other); private: friend class GraphicsRenderer; void* data_; }; Font class Font { public: Font(); Font(const Font& other); Font(const char* file, int ptsize); ~Font(); void load(const char* file, int ptsize); void free(); bool isLoaded() const; Font& operator=(const Font& other); private: friend class GraphicsRenderer; void* data_; }; GrapphicsRenderer class GraphicsRenderer { public: static GraphicsRenderer* Instance(); void blitImage(const Image& img, int x, int y); void blitText(const char* string, const Font& font, int x, int y); void render(); protected: GraphicsRenderer(); GraphicsRenderer(const GraphicsRenderer& other); GraphicsRenderer& operator=(const GraphicsRenderer& other); ~GraphicsRenderer(); private: void* screen_; bool initialize(); void finalize(); };

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• Conflict Minerals - Design to Compliance

  - by C. Chadwick

  Dr. Christina  Schröder - Principal PLM Consultant, Enterprise PLM Solutions EMEA What does the Conflict Minerals regulation mean? Conflict Minerals has recently become a new buzz word in the manufacturing industry, particularly in electronics and medical devices. Known as the "Dodd-Frank Section 1502", this regulation requires SEC listed companies to declare the origin of certain minerals by 2014. The intention is to reduce the use of tantalum, tungsten, tin, and gold which originate from mines in the Democratic Republic of Congo (DRC) and adjoining countries that are controlled by violent armed militia abusing human rights. Manufacturers now request information from their suppliers to see if their raw materials are sourced from this region and which smelters are used to extract the metals from the minerals. A standardized questionnaire has been developed for this purpose (download and further information). Soon, even companies which are not directly affected by the Conflict Minerals legislation will have to collect and maintain this information since their customers will request the data from their suppliers. Furthermore, it is expected that the public opinion and consumer interests will force manufacturers to avoid the use of metals with questionable origin. Impact for existing products Several departments are involved in the process of collecting data and providing conflict minerals compliance information. For already marketed products, purchasing typically requests Conflict Minerals declarations from the suppliers. In order to address requests from customers, technical operations or product management are usually responsible for keeping track of all parts, raw materials and their suppliers so that the required information can be provided. For complex BOMs, it is very tedious to maintain complete, accurate, up-to-date, and traceable data. Any product change or new supplier can, in addition to all other implications, have an effect on the Conflict Minerals compliance status. Influence on product development  It makes sense to consider compliance early in the planning and design of new products. Companies should evaluate which metals are needed or contained in supplier parts and if these could originate from problematic sources. The answer influences the cost and risk analysis during the development. If it is known early on that a part could be non-compliant with respect to Conflict Minerals, alternatives can be evaluated and thus costly changes at a later stage can be avoided. Integrated compliance management  Ideally, compliance data for Conflict Minerals, but also for other regulations like REACH and RoHS, should be managed in an integrated supply chain system. The compliance status is directly visible across the entire BOM at any part level and for the finished product. If data is missing, a request to the supplier can be triggered right away without having to switch to another system. The entire process, from identification of the relevant parts, requesting information, handling responses, data entry, to compliance calculation is fully covered end-to-end while being transparent for all stakeholders. Agile PLM Product Governance and Compliance (PG&C) The PG&C module extends Agile PLM with exactly this integrated functionality. As with the entire Agile product suite, PG&C can be configured according to customer requirements: data fields, attributes, workflows, routing, notifications, and permissions, etc… can be quickly and easily tailored to a customer’s needs. Optionally, external databases can be interfaced to query commercially available sources of Conflict Minerals declarations which obviates the need for a separate supplier request in many cases. Suppliers can access the system directly for data entry through a special portal. The responses to the standard EICC-GeSI questionnaire can be imported by the supplier or internally. Manual data entry is also supported. A set of compliance-specific dashboards and reports complement the functionality Conclusion  The increasing number of product compliance regulations, for which Conflict Minerals is just one example, requires companies to implement an efficient data and process management in this area. Consumer awareness in this matter increases as well so that an integrated system from development to production also provides a competitive advantage. Follow this link to learn more about Agile's PG&C solution

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• Can't remove JPanel from JFrame while adding new class into it

  - by A.K.

  Basically, I have my Frame class, which instantiates all the properties for the JFrame, and draws a JLabel with an image (my title screen). Then I made a separate JPanel with a start button on it, and made a mouse listener that will allow me to remove these objects while adding in a new Board() class (Which paints the main game). *Note: The JLabel is SEPARATE from the JPanel, but it still gets moved to the side by it. Problem: Whenever I click the button though, it only shows a little square of what I presume is my board class trying to run. Code below for the Frame Class: package OurPackage; //Made By A.K. 5/24/12 //Contains Frame. import java.awt.BorderLayout; import java.awt.Color; import java.awt.Container; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GridBagLayout; import java.awt.GridLayout; import java.awt.Image; import java.awt.Rectangle; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import javax.swing.*; import javax.swing.plaf.basic.BasicOptionPaneUI.ButtonActionListener; public class Frame implements MouseListener { public static boolean StartGame = false; ImageIcon img = new ImageIcon(getClass().getResource("/Images/ActionJackTitle.png")); ImageIcon StartImg = new ImageIcon(getClass().getResource("/Images/JackStart.png")); public Image Title; JLabel TitleL = new JLabel(img); public JPanel panel = new JPanel(); JButton StartB = new JButton(StartImg); JFrame frm = new JFrame("Action-Packed Jack"); public Frame() { TitleL.setPreferredSize(new Dimension(1200, 420)); frm.add(TitleL); frm.setLayout(new GridBagLayout()); frm.add(panel); panel.setSize(new Dimension(220, 45)); panel.setLayout(new GridBagLayout ()); panel.add(StartB); StartB.addMouseListener(this); StartB.setPreferredSize(new Dimension(220, 45)); frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frm.setSize(1200, 420); frm.setVisible(true); frm.setResizable(false); frm.setLocationRelativeTo(null); } public static void main(String[] args) { new Frame(); } public void mouseClicked(MouseEvent e) { StartB.setContentAreaFilled(false); panel.remove(StartB); frm.remove(panel); frm.remove(TitleL); //frm.setLayout(null); frm.add(new Board()); //Add Game "Tiles" Or Content. x = 1200 frm.validate(); System.out.println("Hit!"); } @Override public void mouseEntered(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mouseExited(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mousePressed(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mouseReleased(MouseEvent arg0) { // TODO Auto-generated method stub } }

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• How to layout class definition when inheriting from multiple interfaces

  - by gabr

  Given two interface definitions ... IOmniWorkItem = interface ['{3CE2762F-B7A3-4490-BF22-2109C042EAD1}'] function GetData: TOmniValue; function GetResult: TOmniValue; function GetUniqueID: int64; procedure SetResult(const value: TOmniValue); // procedure Cancel; function DetachException: Exception; function FatalException: Exception; function IsCanceled: boolean; function IsExceptional: boolean; property Data: TOmniValue read GetData; property Result: TOmniValue read GetResult write SetResult; property UniqueID: int64 read GetUniqueID; end; IOmniWorkItemEx = interface ['{3B48D012-CF1C-4B47-A4A0-3072A9067A3E}'] function GetOnWorkItemDone: TOmniWorkItemDoneDelegate; function GetOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; procedure SetOnWorkItemDone(const Value: TOmniWorkItemDoneDelegate); procedure SetOnWorkItemDone_Asy(const Value: TOmniWorkItemDoneDelegate); // property OnWorkItemDone: TOmniWorkItemDoneDelegate read GetOnWorkItemDone write SetOnWorkItemDone; property OnWorkItemDone_Asy: TOmniWorkItemDoneDelegate read GetOnWorkItemDone_Asy write SetOnWorkItemDone_Asy; end; ... what are your ideas of laying out class declaration that inherits from both of them? My current idea (but I don't know if I'm happy with it): TOmniWorkItem = class(TInterfacedObject, IOmniWorkItem, IOmniWorkItemEx) strict private FData : TOmniValue; FOnWorkItemDone : TOmniWorkItemDoneDelegate; FOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; FResult : TOmniValue; FUniqueID : int64; strict protected procedure FreeException; protected //IOmniWorkItem function GetData: TOmniValue; function GetResult: TOmniValue; function GetUniqueID: int64; procedure SetResult(const value: TOmniValue); protected //IOmniWorkItemEx function GetOnWorkItemDone: TOmniWorkItemDoneDelegate; function GetOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; procedure SetOnWorkItemDone(const Value: TOmniWorkItemDoneDelegate); procedure SetOnWorkItemDone_Asy(const Value: TOmniWorkItemDoneDelegate); public constructor Create(const data: TOmniValue; uniqueID: int64); destructor Destroy; override; public //IOmniWorkItem procedure Cancel; function DetachException: Exception; function FatalException: Exception; function IsCanceled: boolean; function IsExceptional: boolean; property Data: TOmniValue read GetData; property Result: TOmniValue read GetResult write SetResult; property UniqueID: int64 read GetUniqueID; public //IOmniWorkItemEx property OnWorkItemDone: TOmniWorkItemDoneDelegate read GetOnWorkItemDone write SetOnWorkItemDone; property OnWorkItemDone_Asy: TOmniWorkItemDoneDelegate read GetOnWorkItemDone_Asy write SetOnWorkItemDone_Asy; end; As noted in answers, composition is a good approach for this example but I'm not sure it applies in all cases. Sometimes I'm using multiple inheritance just to split read and write access to some property into public (typically read-only) and private (typically write-only) part. Does composition still apply here? I'm not really sure as I would have to move the property in question out from the main class and I'm not sure that's the correct way to do it. Example: // public part of the interface interface IOmniWorkItemConfig = interface function OnExecute(const aTask: TOmniBackgroundWorkerDelegate): IOmniWorkItemConfig; function OnRequestDone(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; function OnRequestDone_Asy(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; end; // private part of the interface IOmniWorkItemConfigEx = interface ['{42CEC5CB-404F-4868-AE81-6A13AD7E3C6B}'] function GetOnExecute: TOmniBackgroundWorkerDelegate; function GetOnRequestDone: TOmniWorkItemDoneDelegate; function GetOnRequestDone_Asy: TOmniWorkItemDoneDelegate; end; // implementing class TOmniWorkItemConfig = class(TInterfacedObject, IOmniWorkItemConfig, IOmniWorkItemConfigEx) strict private FOnExecute : TOmniBackgroundWorkerDelegate; FOnRequestDone : TOmniWorkItemDoneDelegate; FOnRequestDone_Asy: TOmniWorkItemDoneDelegate; public constructor Create(defaults: IOmniWorkItemConfig = nil); public //IOmniWorkItemConfig function OnExecute(const aTask: TOmniBackgroundWorkerDelegate): IOmniWorkItemConfig; function OnRequestDone(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; function OnRequestDone_Asy(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; public //IOmniWorkItemConfigEx function GetOnExecute: TOmniBackgroundWorkerDelegate; function GetOnRequestDone: TOmniWorkItemDoneDelegate; function GetOnRequestDone_Asy: TOmniWorkItemDoneDelegate; end;

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• How can I cleanly and elegantly handle data and dependancies between classes

  - by Neophyte

  I'm working on 2d topdown game in SFML 2, and need to find an elegant way in which everything will work and fit together. Allow me to explain. I have a number of classes that inherit from an abstract base that provides a draw method and an update method to all the classes. In the game loop, I call update and then draw on each class, I imagine this is a pretty common approach. I have classes for tiles, collisions, the player and a resource manager that contains all the tiles/images/textures. Due to the way input works in SFML I decided to have each class handle input (if required) in its update call. Up until now I have been passing in dependencies as needed, for example, in the player class when a movement key is pressed, I call a method on the collision class to check if the position the player wants to move to will be a collision, and only move the player if there is no collision. This works fine for the most part, but I believe it can be done better, I'm just not sure how. I now have more complex things I need to implement, eg: a player is able to walk up to an object on the ground, press a key to pick it up/loot it and it will then show up in inventory. This means that a few things need to happen: Check if the player is in range of a lootable item on keypress, else do not proceed. Find the item. Update the sprite texture on the item from its default texture to a "looted" texture. Update the collision for the item: it might have changed shape or been removed completely. Inventory needs to be updated with the added item. How do I make everything communicate? With my current system I will end up with my classes going out of scope, and method calls to each other all over the place. I could tie up all the classes in one big manager and give each one a reference to the parent manager class, but this seems only slightly better. Any help/advice would be greatly appreciated! If anything is unclear, I'm happy to expand on things.

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