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• What is the correct pattern to use in this case?

  - by nulliusinverba

  I'm sure this scenario has arisen before, and I want to know what experience has taught to be the best solution. I have a number of classes that are all of a kind. Say all the objects are "Content". They may be "Article", or "Book" for example. The reason I want the "Content" abstraction is because I want to define a number of behaviours for all "Content" objects and not have to build a new DB Table and 10 classes of essentially the same code for each type of "Content". For example, to attach a "Tag" or a "Premise" to a content object would be much nicer if, say, I just had two columns one for ContentID and one for TagID. A solution I've played around with is to have a Content table with a unique ID, and then to have foreign key references on all the other tables (Book, Article, etc). This has actually proven quite solid, but I'm just not sure about it. Do you know how to call this described pattern?

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• Installing purchased apps by terminal

  - by DoDoGo

  I've been trying to reinstall all my purchased apps on a new machine, and I ran into a problem. Because of the size of them (about 10-12GB in total) and the fact that downloading them is painfully slow for whatever reason (at most 800kB/s), it takes a lot of time (not to mention USC crashing). And then, when I tried to leave them overnight, none of them were installed and everything was at the same spot I left it. Is there anyway to install them via terminal? Like some kind of USC backend were I could just add the archives for apps listed as purchased and then install them via apt-get?

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• Designing a user-defined list to be stored in a relational database - Should I include user index?

  - by Zaemz

  By index, I mean, as the user creates the list, each item receives an integer index for its place in that particular list. Since there will be a table of ListItems, I'd prefer to avoid using the name "Index" for the field. Then I was thinking - should I even include the list index in the database? I figured I would because the list would be created in the same fashion every time, then. Or I could order the list for the user based on its actual primary key, since the list items are created in succession anyway... What should I do?

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• How can I implement a matchmaker?

  - by csiz

  I'm making a multiplayer game, where players are separated in to rooms that would ideally have about 20 players. So I need a few pointers on an algorithm to distribute the players in to these rooms. A few more constraints: When a players gets in to a room, he should stay there until he decides to exit (the room itself changes levels) There may be more room servers, every server should create more rooms until near full capacity There's a central server that manages all the room servers, and directs the players towards their room

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• How to install CREBS on Ubuntu 14.04?

  - by user288556

  I tried installing CREBS on Ubuntu 14.04. unfortunately the repository installation doesn't work, so I decided to download the source code. But after following their instructions(namely running setup.sh as root) I get this error when typing "crebs" in a terminal: Traceback (most recent call last): File "/usr/local/bin/crebs", line 38, in <module> from crebs.main import main File "/usr/local/bin/../share/crebs/lib/crebs/__init__.py", line 6, in <module> from gtk import glade ImportError: cannot import name glade any hint? thank you

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• Does anyone know of a program like Elastics for Linux?

  - by coteyr

  On mac I would use Elastics (http://tundrabot.com/elastics) To kind of, monitor my EC2 instances. Most important to me was that it worked across several accounts and that it allowed me to connect to a running instance via ssh or RDP. This was the only real feature I care about. I can not always keep the IP address of the server that is running because ec2 is elastic, and it changes frequently. Is there any tool, like Elastics for linux/unity? Again it should support several accounts and be able to give me the IP addresses of the instance I select.

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• Is there a language that allows this syntax: add(elements)at(index);

  - by c_maker

  Does a language exist with such a syntax? If not, what are some of the limitations/disadvantages to this syntax in case I want to write a language that supported it? Some examples: sort(array, fromIndex, toIndex); vs sort(array)from(index1)to(index2); Method signature would like this: sort(SomeType[] arr)from(int begin)to(int end){ ... } Update: Because there might be some confusion, I'd like to clarify... I meant this question as a general idea like this (not specific to sorting and possibly using keywords like from and to): In JAVA(like language): void myfancymethod(int arg1, String arg2){ ... } myfancymethod(1, "foo"); In imaginary language: void my(int arg1)fancy(String arg2)method{ ... } my(1)fancy("foo")method;

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• Drag and Drop Team Selection

  - by davidjwest

  I have a Fantasy F1 Website, currently users select their teams using dropdown menus. It works OK but isn't as user friendly as I would like. I would like to implement a drag and drop type of system, there's jQuery code out there that would go part of the way to allowing me to do this: http://jqueryui.com/demos/draggable/ But I am not sure about how to integrate that into PHP and MySQL, my jQuery skills are limited! I'd also need to stop them spending more than a certain amount of money, each driver has a value and the teams can only spend a certain amount of money. There's also limits for example you can only pick a driver once, but you can have three different drivers. Finally, how would you decide that the user had picked their team, I don't want a submit button as that kind of defeats the object of the exercise! Thanks for any advice, I don't expect anyone to write the code for me but some pointers would be greatly appreciated.

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• Greenspun's Tenth Rule, does every large project include a Lisp interpreter?

  - by casualcoder

  Greenspun's tenth rule (actually the only rule) states that: Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp. My memory is that there are some papers on the topic, perhaps for Borland's Quattro (spreadsheet) project and possibly others. Google is unhelpful, maybe the right search terms are not coming to mind. I am looking for papers or articles supporting this claim, if any.

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• What is the preferred pattern when attaching a 'runtime object'?

  - by sebf

  In my application I have the following: public class NeatObject { /* lots of static data, and configuration flags */ } public class NeatObjectConsumer { void DoCleverStuffWithObjectOnGPU(NeatObject obj); } Where NeatObject and its consumer are used to control the GPU. The idea being that, the configuration of an instance of NeatObject and its members, define how the consumer instance behaves. The object can be passed around, edited, and most importantly serialised/deserialised by the application, with and without knowledge of NeatObjectConsumer, then provided back to the consumer to do something else. The purpose of this seperation is: The consumer manages hardware resources, which change depending on the computer, and even on the execution of the application, making preserving the state of an object which does everything difficult. Avoids circular references if the assembly that contains the consumer needs to reference one that only needs to know about NeatObject. However, there is a complication in that the consumer creates hardware resources and needs to associate them with NeatObject. These don't need to be preserved, but still need to be retrieved. DoCleverStuffWithObjectOnGPU() will be called many, many times during execution and so any bottleneck is a concern, therefore I would like to avoid dictionary lookups. What is the preferred method of attaching this information to NeatObject? By preferred, I mean intuitive - other coders can see immediately what is going on - and robust - method doesn't invite playing with the resources or present them in such a way as to make them easily corruptible. Essentially, I want to add my own metadata - how should I do it? Try to use 'actual metadata' functionality like Reflection? A member of the type of an abstract class? Unmanaged pointers? If you took on a project that used this pattern, what would you have liked the previous developer to do?

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• User input and automated input separation

  - by tpaksu

  I have a MySQL database and an automation script which modifies the data inside once a day. And these columns may have changed by an user manually. What is the best approach to make the system only update the automated data, not the manually edited ones? I mean yes, flagging the cell which is manually edited is one way to do it, but I want to know if there's another way to accomplish this? Just curiosity. BTW, the question is about cell values, not rows.

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• What class structure allows for a base class and mix/match of subclasses? (Similar to Users w/ roles)

  - by cdeszaq

  I have a set of base characteristics, and then a number of sub-types. Each instance must be one of the sub-types, but can be multiple sub-types at once. The sub-types of each thing can change. In general, I don't care what subtype I have, but sometimes I do care. This is much like a Users-Roles sort of relationship where a User having a particular Role gives the user additional characteristics. Sort of like duck-typing (ie. If my Foo has a Bar, I can treat it like a ThingWithABar.) Straight inheritance doesn't work, since that doesn't allow mix/match of sub-types. (ie. no multi-inheritance). Straight composition doesn't work because I can't switch that up at runtime. How can I model this?

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• Best Way to Handle Meta Information in a SQL Database

  - by danielhanly.com

  I've got a database where I want to store user information and user_meta information. The reason behind setting it up in this way was because the user_meta side may change over time and I would like to do this without disrupting the master user table. If possible, I would like some advice on how to best set up this meta data table. I can either set it as below: +----+---------+----------+--------------------+ | id | user_id | key | value | +----+---------+----------+--------------------+ | 1 | 1 | email | [email protected] | | 2 | 1 | name | user name | | 3 | 1 | address | test address | ... Or, I can set it as below: +----+---------+--------------------+--------------------+--------------+ | id | user_id | email | name | address | +----+---------+--------------------+--------------------+--------------+ | 1 | 1 | [email protected] | user name | test address | Obviously, the top verison is more flexible, but the bottom version is space saving and perhaps more efficient, returning all the data as a single record. Which is the best way to go about this? Or, am I going about this completely wrong and there's another way I've not thought of?

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• Testing complex compositions

  - by phlipsy

  I have a rather large collection of classes which check and mutate a given data structure. They can be composed via the composition pattern into arbitrarily complex tree-like structures. The final product contains a lot of these composed structures. My question is now: How can I test those? Albeit it is easy to test every single unit of these compositions, it is rather expensive to test the whole compositions in the following sense: Testing the correct layout of the composition-tree results in a huge number of test cases Changes in the compositions result in a very laborious review of every single test case What is the general guideline here?

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• PHP class data implementation

  - by Bakanyaka

  I'm studying OOP PHP and have watched two tutorials that implement user login\registration system as an example. But implementation varies. Which way will be more correct one to work with data such as this? Load all data retrieved from database as array into a property called something like _data on class creation and further methods operate with this property Create separate properties for each field retrieved from database, on class creation load all data fields into respective properties and operate with that properties separately? Then let's say I want to create a method that returns a list of all users with their data. Which way is better? Method that returns just an array of userdata like this: Array([0]=>array([id] => 1, [username] => 'John', ...), [1]=>array([id] => 2, [username] => 'Jack', ...), ...) Method that creates a new instance of it's class for each user and returns an array of objects

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• Is this a valid implementation of the repository pattern?

  - by user1578653

  I've been reading up about the repository pattern, with a view to implementing it in my own application. Almost all examples I've found on the internet use some kind of existing framework rather than showing how to implement it 'from scratch'. Here's my first thoughts of how I might implement it - I was wondering if anyone could advise me on whether this is correct? I have two tables, named CONTAINERS and BITS. Each CONTAINER can contain any number of BITs. I represent them as two classes: class Container{ private $bits; private $id; //...and a property for each column in the table... public function __construct(){ $this->bits = array(); } public function addBit($bit){ $this->bits[] = $bit; } //...getters and setters... } class Bit{ //some properties, methods etc... } Each class will have a property for each column in its respective table. I then have a couple of 'repositories' which handle things to do with saving/retrieving these objects from the database: //repository to control saving/retrieving Containers from the database class ContainerRepository{ //inject the bit repository for use later public function __construct($bitRepo){ $this->bitRepo = $bitRepo; } public function getById($id){ //talk directly to Oracle here to all column data into the object //get all the bits in the container $bits = $this->bitRepo->getByContainerId($id); foreach($bits as $bit){ $container->addBit($bit); } //return an instance of Container } public function persist($container){ //talk directly to Oracle here to save it to the database //if its ID is NULL, create a new container in database, otherwise update the existing one //use BitRepository to save each of the Bits inside the Container $bitRepo = $this->bitRepo; foreach($container->bits as $bit){ $bitRepo->persist($bit); } } } //repository to control saving/retrieving Bits from the database class BitRepository{ public function getById($id){} public function getByContainerId($containerId){} public function persist($bit){} } Therefore, the code I would use to get an instance of Container from the database would be: $bitRepo = new BitRepository(); $containerRepo = new ContainerRepository($bitRepo); $container = $containerRepo->getById($id); Or to create a new one and save to the database: $bitRepo = new BitRepository(); $containerRepo = new ContainerRepository($bitRepo); $container = new Container(); $container->setSomeProperty(1); $bit = new Bit(); $container->addBit($bit); $containerRepo->persist($container); Can someone advise me as to whether I have implemented this pattern correctly? Thanks!

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• Starting With Desktop Apps [closed]

  - by perl.j

  I've been programming for a while now. It is a great hobby for me! Actually, It's my only hobby! But I haven't really programmed in a specific area i.e. desktop, web, etc.. After a long while of research, I've decided to jump into making Desktop Applications. But how should I go about doing this? Are there languages that are used to do this, or is it possible to use Python, Perl, C, etc. to make vivid, "amazing-quality", "highly functional" Desktop Apps? Also, what are some good resources to begin learning this? Thanks!

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• Significant amount of the time, I can't think of a reason to have an object instead of a static class. Do objects have more benefits than I think?

  - by Prog

  I understand the concept of an object, and as a Java programmer I feel the OO paradigm comes rather naturally to me in practice. However recently I found myself thinking: Wait a second, what are actually the practical benefits of using an object over using a static class (with proper encapsulation and OO practices)? I could think of two benefits of using an object (both significant and powerful): Polymorphism: allows you to swap functionality dynamically and flexibly during runtime. Also allows to add new functionality 'parts' and alternatives to the system easily. For example if there's a Car class designed to work with Engine objects, and you want to add a new Engine to the system that the Car can use, you can create a new Engine subclass and simply pass an object of this class into the Car object, without having to change anything about Car. And you can decide to do so during runtime. Being able to 'pass functionality around': you can pass an object around the system dynamically. But are there any more advantages to objects over static classes? Often when I add new 'parts' to a system, I do so by creating a new class and instantiating objects from it. But recently when I stopped and thought about it, I realized that a static class would do just the same as an object, in a lot of the places where I normally use an object. For example, I'm working on adding a save/load-file mechanism to my app. With an object, the calling line of code will look like this: Thing thing = fileLoader.load(file); With a static class, it would look like this: Thing thing = FileLoader.load(file); What's the difference? Fairly often I just can't think of a reason to instantiate an object when a plain-old static-class would act just the same. But in OO systems, static classes are fairly rare. So I must be missing something. Are there any more advantages to objects other from the two that I listed? Please explain.

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• How to install aircrack on Ubuntu 12.04

  - by user287903

  I have downloaded the tar.gz package from the site and then I have extracted using tar -zxvf command as mentioned over there. After that I used sudo apt-get install build-essential then I further installed libssl-dev. Then I changed directory to the aircrack folder. But when I type either sudo make or just make I am getting this same error. I don't know what to do. I have installed the file what they have asked in the error as well. Still the same error is shown. Okay I am not permitted to upload images. The error is : common.mak:85: *** Cannot find development files for any supported version of libnl. install either libnl1 or libnl3.. Stop.

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• IXRepository and test problems

  - by Ridermansb

  Recently had a doubt about how and where to test repository methods. Let the following situation: I have an interface IRepository like this: public interface IRepository<T> where T: class, IEntity { IQueryable<T> Query(Expression<Func<T, bool>> expression); // ... Omitted } And a generic implementation of IRepository public class Repository<T> : IRepository<T> where T : class, IEntity { public IQueryable<T> Query(Expression<Func<T, bool>> expression) { return All().Where(expression).AsQueryable(); } } This is an implementation base that can be used by any repository. It contains the basic implementation of my ORM. Some repositories have specific filters, in which case we will IEmployeeRepository with a specific filter: public interface IEmployeeRepository : IRepository<Employee> { IQueryable<Employee> GetInactiveEmployees(); } And the implementation of IEmployeeRepository: public class EmployeeRepository : Repository<Employee>, IEmployeeRepository // TODO: I have a dependency with ORM at this point in Repository<Employee>. How to solve? How to test the GetInactiveEmployees method { public IQueryable<Employee> GetInactiveEmployees() { return Query(p => p.Status != StatusEmployeeEnum.Active || p.StartDate < DateTime.Now); } } Questions Is right to inherit Repository<Employee>? The goal is to reuse code once all implementing IRepository already been made. If EmployeeRepository inherit only IEmployeeRepository, I have to literally copy and paste the code of Repository<T>. In our example, in EmployeeRepository : Repository<Employee> our Repository lies in our ORM layer. We have a dependency here with our ORM impossible to perform some unit test. How to create a unit test to ensure that the filter GetInactiveEmployees return all Employees in which the Status != Active and StartDate < DateTime.Now. I can not create a Fake/Mock of IEmployeeRepository because I would be testing? Need to test the actual implementation of GetInactiveEmployees. The complete code can be found on Github

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• Requiring a specific order of compilaiton

  - by Aber Kled

  When designing a compiled programming language, is it a bad idea to require a specific order of compilation of separate units, according to their dependencies? To illustrate what I mean, consider C. C is the opposite of what I'm suggesting. There are multiple .c files, that can all depend on each other, but all of these separate units can be compiled on their own, in no particular order - only to be linked together into a final executable later. This is mostly due to header files. They enable separate units to share information with each other, and thus the units are able to be compiled independently. If a language were to dispose of header files, and only keep source and object files, then the only option would be to actually include the unit's meta-information in the unit's object file. However, this would mean that if the unit A depends on the unit B, then the unit B would need to be compiled before unit A, so unit A could "import" the unit B's object file, thus obtaining the information required for its compilation. Am I missing something here? Is this really the only way to go about removing header files in compiled languages?

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• "Do it right, against customer's wishes" - how is it called?

  - by SF.

  We know the optimal situation of negotiating corrections of specifications with the customer, getting the specs to do what the client wanted, not what they said or thought they wanted. That's negotiating, explaining. Sometimes, we're unable to convince the client. We're forced to produce broken as designed. This, called "demonology" by merit of mages summoning demons and demons fulfilling their wishes very literally, causing the mage's demise as result, is another approach that will leave the customer very dissatisfied once they realize their error, and of course try to pin the blame on the developer. Now I just faced a very different approach: the customer created simple specs that fail to account for some critical caveat, and is completely unwilling to fix them, admit the obvious errors and accept suggested corrections. The product made to these specs will be critically broken, and possibly might cost human lives. Still, it's too late to drop the contract entirely. The contract has punitive clauses for that, ones we can't really accept. The boss' decision? We do the work right and lie to the customer that we did it according to the specs. The algorithms in question are hidden deep enough under the surface, the product will do the work just fine, won't fail in the caveat situation, and unless someone digs too deep, they will never discover we didn't break it as requested. Is there some common name for this tactics of execution of specs?

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• Versioning Java APIs in a non-web context

  - by GAP

  I have modular java application which consists of 40 modules. Some of these modules needs to expose external APIs which other modules or any external integration should be using. The system runs as a desktop application and each module is bundled as a separate jar file. My plan is to bundle the external api as a separate jar. But now the question is: how can I maintain multiple versions of the same API to keep backward compatibility in cases where it can co-exist? Are there any de facto standards on handling APIs versioning out of a web context ?

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• Do I need to add an index on a table with one row?

  - by briddums

  I'm creating a parameter table in our database. This table will have 1 row with values that are environment specific (production, development, etc). Is there any reason why I should define an index on this table? Update This table is a parameter table which will be used to drive our job queue system. The table will be defined like this: QueuePrm LogLvl integer ShowMs boolean Restart boolean This table will only ever have 1 row. No other table in our system will reference it.

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• Any tips/tricks/resources on actually TEACHING a class on OOP? [closed]

  - by Sempus

  I may slowly be getting into teaching an Object-Orientated Programming class at my school in a year or two. I just graduated and work at my school as an Application Programmer. I'd first start off as a TA/grader and then slowly move into the Professor role. The class would be in Java. I always see resources on this fine site about HOW to program, but does anyone know any tips/tricks/resources on how to TEACH a programming class? It would be full of all different skills levels(but still semi-technical) so it would have to be a little more understandable than if it was just CS kids.

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