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• Is it wrong to use a boolean parameter to determine behavior?

  - by Ray

  I have seen a practice from time to time that "feels" wrong, but I can't quite articulate what is wrong about it. Or maybe it's just my prejudice. Here goes: A developer defines a method with a boolean as one of its parameters, and that method calls another, and so on, and eventually that boolean is used, solely to determine whether or not to take a certain action. This might be used, for example, to allow the action only if the user has certain rights, or perhaps if we are (or aren't) in test mode or batch mode or live mode, or perhaps only when the system is in a certain state. Well there is always another way to do it, whether by querying when it is time to take the action (rather than passing the parameter), or by having multiple versions of the method, or multiple implementations of the class, etc. My question isn't so much how to improve this, but rather whether or not it really is wrong (as I suspect), and if it is, what is wrong about it.

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• How to implement Restricted access to application features

  - by DroidUser

  I'm currently developing a web application, that provides some 'service' to the user. The user will have to select a 'plan' according to which she/he will be allowed to perform application specific actions but up to a limit defined by the plan. A Plan will also limit access to certain features, which will not be available at all for some plans. As an example : say there are 3 plans, 2 actions throughout the application users in plan-1 can perform action-1 3 times, and they can't perform action-2 at all users in plan-2 can perform action-1 10 times, action-2 5 times users in plan-3 can perform action-1 20 times, action-2 10 times So i'm looking for the best way to get this done, and my main concerns besides implementing it, are the following(in no particular order) maintainability/changeability : the number of plans, and type of features/actions will change in the final product industry standard/best practice : for future readiness!! efficiency : ofcourse, i want fast code!! I have never done anything like this before, so i have no clue about how do i go about implementing these functionalities. Any tips/guides/patterns/resources/examples? I did read a little about ACL, RBAC, are they the patterns that i need to follow? Really any sort of feedback will help.

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• How would you model an objects representing different phases of an entity life cycle?

  - by Ophir Yoktan

  I believe the scenario is common mostly in business workflows - for example: loan management the process starts with a loan application, then there's the loan offer, the 'live' loan, and maybe also finished loans. all these objects are related, and share many fields all these objects have also many fields that are unique for each entity the variety of objects maybe large, and the transformation between the may not be linear (for example: a single loan application may end up as several loans of different types) How would you model this? some options: an entity for each type, each containing the relevant fields (possibly grouping related fields as sub entities) - leads to duplication of data. an entity for each object, but instead of duplicating data, each object has a reference to it's predecessor (the loan doesn't contain the loaner details, but a reference to the loan application) - this causes coupling between the object structure, and the way it was created. if we change the loan application, it shouldn't effect the structure of the loan entity. one large entity, with fields for the whole life cycle - this can create 'mega objects' with many fields. it also doesn't work well when there's a one to many or many to many relation between the phases.

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• Create many similar classes, or just one

  - by soandos

  The goal is to create an application that has objects that can represent some operations (add, subtract, etc). All of those objects will have common functions and members, and thus will either implement an interface or inherit from an abstract class (Which would be better practice, this will be in C# if that matters?). As far as I can see, there are two different ways of organizing all of these classes. I could create an addition class, a subtraction class, etc. This has the upside of being highly modular but the difference between classes is so minimal. I could create one class, and have a member that will say what type of operation is being represented. This means lots of switch statements, and losing some modularity, in addition to being harder to maintain. Which is is better practice? Is there a better way of doing that is not listed above? If it matters, the list of functions that should be supported is long.

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• Why avoid Java Inheritance "Extends"

  - by newbie

  Good day! Jame Gosling said “You should avoid implementation inheritance whenever possible.” and instead, use interface inheritance. But why? How can we avoid inheriting the structure of an object using the keyword "extends", and at the same time make our code Object Oriented? Could someone please give an Object Oriented example illustrating this concept in a scenario like "ordering a book in a bookstore?" Thank you in advance.

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• How to refactor to cleaner version of maintaing states of the widget

  - by George

  Backstory I inherited a bunch of code that I'd like to refactor. It is a UI application written in javascript. Current state: We have main application which consist of several UI components. And each component has entry fields, textboxes, menus, etc), like "ticket", "customer information", etc. Based on input, where the application was called from, who is the user, we enable/disable, hide, show, change titles. Unfortunately, the app grew to the point where it is really hard to scale, add new features. Main the driver (application code) calls set/unset functions of the respective components. So a lot of the stuff look like this Main app unit function1() { **call_function2()** component1.setX(true); component1.setY(true); component2.setX(false); } call_function2() { // it may repeat some of the code function1 called } and we have a lot of this in the main union. I am cleaning this mess. What is the best way to maintain the state of widgets? Please let me know if you need me to clarify.

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• Where we should put validation for domain model

  - by adisembiring

  I still looking best practice for domain model validation. Is that good to put the validation in constructor of domain model ? my domain model validation example as follows: public class Order { private readonly List<OrderLine> _lineItems; public virtual Customer Customer { get; private set; } public virtual DateTime OrderDate { get; private set; } public virtual decimal OrderTotal { get; private set; } public Order (Customer customer) { if (customer == null) throw new ArgumentException("Customer name must be defined"); Customer = customer; OrderDate = DateTime.Now; _lineItems = new List<LineItem>(); } public void AddOderLine //.... public IEnumerable<OrderLine> AddOderLine { get {return _lineItems;} } } public class OrderLine { public virtual Order Order { get; set; } public virtual Product Product { get; set; } public virtual int Quantity { get; set; } public virtual decimal UnitPrice { get; set; } public OrderLine(Order order, int quantity, Product product) { if (order == null) throw new ArgumentException("Order name must be defined"); if (quantity <= 0) throw new ArgumentException("Quantity must be greater than zero"); if (product == null) throw new ArgumentException("Product name must be defined"); Order = order; Quantity = quantity; Product = product; } } Thanks for all of your suggestion.

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• Where ORMs blur the lines between code and data, how do you decide what logic should be a stored procedure, and what should be coded?

  - by PhonicUK

  Take the following pseudocode: CreateInvoiceAndCalculate(ItemsAndQuantities, DispatchAddress, User); And say CreateInvoice does the following: Create a new entry in an Invoices table belonging to the specified User to be sent to the given DispatchAddress. Create a new entry in an InvoiceItems table for each of the items in ItemsAndQuantities, storing the Item, the Quantity, and the cost of the item as of now (by looking it up from an Items table) Calculate the total amount of the invoice (ex shipping and taxes) and store it in the new Invoice row. At a glace you wouldn't be able to tell if this was a method in my applications code, or a stored procedure in the database that is being exposed as a function by the ORM. And to some extent it doesn't really matter. Now technically none of this is business logic. You're not making any decisions - just performing a calculation and creating records. However some may argue that because you are performing a calculation that affects the business (the total amount to be invoiced) that this isn't something that should be done in a stored procedure and instead should be in code. So for this specific example - why would it be more appropriate to do one or the other? And where do you draw the line? Or does it even particular matter as long as it's sufficiently well documented?

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• Interfaces on an abstract class

  - by insta

  My coworker and I have different opinions on the relationship between base classes and interfaces. I'm of the belief that a class should not implement an interface unless that class can be used when an implementation of the interface is required. In other words, I like to see code like this: interface IFooWorker { void Work(); } abstract class BaseWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker, IFooWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } The DbWorker is what gets the IFooWorker interface, because it is an instantiatable implementation of the interface. It completely fulfills the contract. My coworker prefers the nearly identical: interface IFooWorker { void Work(); } abstract class BaseWorker : IFooWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } Where the base class gets the interface, and by virtue of this all inheritors of the base class are of that interface as well. This bugs me but I can't come up with concrete reasons why, outside of "the base class cannot stand on its own as an implementation of the interface". What are the pros & cons of his method vs. mine, and why should one be used over another?

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• How do I decide to which class a method should belong

  - by Eleeist

  I have TopicBusiness.class and PostBusiness.class. I have no problem with deciding into which class methods such as addPostToDatabase() or getAllPostsFromDatabase() should go. But what about getAllPostsFromTopic(TopicEntity topic) or getNumberOfPostsInTopic(TopicEntity topic)? Should the parameter be the deciding factor? So when the method takes TopicEntity as parameter it should belong to TopicBusiness.class? I am quite puzzled by this. EDIT: Some more info as requested. TopicBusiness.class and PostBusiness.class are classes holding all the business logic of the application concerning topics and posts respectively - that is fetching the data from database and/or performing some operations on them. TopicEntity is data (in this case representing single topic) fetched from database. getAllPostFromTopic(TopicEntity topic) gets all posts from database that belong to particular topic, while getNumberOfPostsInTopic(TopicEntity topic) performs database query and returns the number of posts that topic passed as parameter consists of.

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• When is a glue or management class doing too much?

  - by jprete

  I'm prone to building centralized classes that manage the other classes in my designs. It doesn't store everything itself, but most data requests would go to the "manager" first. While looking at an answer to this question I noticed the term "God Object". Wikipedia lists it as an antipattern, understandably. Where is the line between a legitimate glue class, or module, that passes data and messages from place to place, and a class that is doing too much?

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• How to layer if statements when order of logic is irrelevant?

  - by jimmyjimmy

  Basically I have a series of logic in my website that can lead to 5 total outcomes. Basically two different if tests and then a catch all else statement. For example: if cond1: if mod1: #do things elif mod2: #do things elif cond2: if mod1: #do things elif mod2 #do things else: #do things I was thinking about rewriting it like this: if cond1 and mod1: #do things elif cond1 and mod2: #do things elif cond2 and mod1: #do things elif cond2 and mod2: #do things else: #do things Is there any real difference in these two coding options/a better choice for this kind of logic testing?

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• Visitor-pattern vs inheritance for rendering

  - by akaltar

  I have a game engine that currently uses inheritance to provide a generic interface to do rendering: class renderable { public: void render(); }; Each class calls the gl_* functions itself, this makes the code hard to optimize and hard to implement something like setting the quality of rendering: class sphere : public renderable { public: void render() { glDrawElements(...); } }; I was thinking about implementing a system where I would create a Renderer class that would render my objects: class sphere { void render( renderer* r ) { r->renderme( *this ); } }; class renderer { renderme( sphere& sphere ) { // magically get render resources here // magically render a sphere here } }; My main problem is where should I store the VBOs and where should I Create them when using this method? Should I even use this approach or stick to the current one, perhaps something else? PS: I already asked this question on SO but got no proper answers.

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• Developing web sites that imitate desktop apps. How to fight that paradigm? [closed]

  - by user1598390

  Supposse there's a company where web sites/apps are designed to resemble desktop apps. They struggle to add: Splash screens Drop-down menus Tab-pages Pages that don't grow downward with content, context is inside scrollable area so page is of a fixed size, as if resembling the one-screen limitation of desktop apps. Modal windows, pop-ups, etc. Tree views Absolutely no access to content unless you login-first, even with non-sensitive content. After splash screen desapears, you are presented with a login screen. No links - just simulated buttons. Fixed page-size. Cannot open a linked in other tab Print button that prints directly ( not showing printable page so the user can't print via the browser's print command ) Progress bars for loading content even when the browser indicates it with its own animation Fonts and color amulate a desktop app made with Visual Basic, PowerBuilder etc. Every app seems almost as if were made in Visual Basic. They reject this elements: Breadcrumbs Good old underlined links Generated/dynamic navigation, usage-based suggestions Ability to open links in multiple tabs Pagination Printable pages Ability to produce a URL you can save or share that links to an item, like when you send someone the link to an especific StackExchange question. The only URL is the main one. Back button To achieve this, tons of javascript code is needed. Lots and lots of Javascript and Ajax code for things not related with the business but with the necessity to hide/show that button, refresh this listbox, grey-out that label, etc. The coplexity generated by forcing one paradigm into another means most lines of code are dedicated to maintain the illusion of a desktop app. What is the best way to change this mindset, and make them embrace the web, and start producing modern, web apps instead of desktop imitations ? EDIT: These sites are intranet sites. Users hate these apps. They constantly whine about them, but they have to use them to do their daily work. These sites are in-house solutions, the end-users have no choice but to use them. They are a "captive audience". Also, substitution will not happen because of high costs. But at least if that mindset is changed, new developments would be more web-like.

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• Should this code/logic be included in Business Objects class or a separate class?

  - by aspdotnetuser

  I have created a small application which has a three tier architecture and I have business object classes to represent entities such as User, Orders, UserType etc. In these classes I have methods that are executed when the Constuctor method of, for example, User is called. These methods perform calculations and generate details that setup data for attributes that are part of each User object. Here is the structure for the project in Visual Studio: Here is some code from the business object class User.cs: Public Class User { public string Name { get; set; } public int RandomNumber { get; set; } etc public User { Name = GetName(); RandomNumber = GetRandomNumber(); } public string GetName() { .... return name; } public int GetRandomNumber() { ... return randomNumber; } } Should this logic be included in the Business Object classes or should it be included in a Utilities class of some kind? Or in the business rules?

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• How to model an address type in DDD?

  - by Songo

  I have an User entity that has a Set of Address where Address is a value object: class User{ ... private Set<Address> addresses; ... public setAddresses(Set<Address> addresses){ //set all addresses as a batch } ... } A User can have a home address and a work address, so I should have something that acts as a look up in the database: tbl_address_type ------------------------------------------------ | address_type_id | address_type | ------------------------------------------------ | 1 | work | ------------------------------------------------ | 2 | home | ------------------------------------------------ and correspondingly tbl_address ------------------------------------------------------------------------------------- | address_id | address_description |address_type_id| user_id | ------------------------------------------------------------------------------------- | 1 | 123 main street | 1 | 100 | ------------------------------------------------------------------------------------- | 2 | 456 another street | 1 | 100 | ------------------------------------------------------------------------------------- | 3 | 789 long street | 2 | 200 | ------------------------------------------------------------------------------------- | 4 | 023 short street | 2 | 200 | ------------------------------------------------------------------------------------- Should the address type be modeled as an Entity or Value type? and Why? Is it OK for the Address Value object to hold a reference to the Entity AdressType (in case it was modeled as an entity)? Is this something feasible using Hibernate/NHibernate? If a user can change his home address, should I expose a User.updateHomeAddress(Address homeAddress) function on the User entity itself? How can I enforce that the client passes a Home address and not a work address in this case? (a sample implementation is most welcomed) If I want to get the User's home address via User.getHomeAddress() function, must I load the whole addresses array then loop it and check each for its type till I found the correct type then return it? Is there a more efficient way than this?

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• Create Levels using blender

  - by notrodash

  I am creating a game and I have a custom level format for levels in my game. I wanted to know if it is possible to create levels for that kinda format in Blender. My format is XML based and just declares the positions of certain objects. Online I have seen many people use Blender to create levels in their own custom format that blender can understand. How do i get blender to understand my format and use blender to create levels for my game?

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• Should interface only be used for behavior and not to show logical data grouped together?

  - by jags

  Should an interface only be used to specify certain behavior? Would it be wrong to use interface to group logically related data? To me it looks like we should not use interface to group logically related data as structure seems a better fit. A class may be used but class name should indicate something like DTO so that user gets the impression that class does not have any behavior. Please let me know if my assumption is correct. Also, are there any exceptions where interface can be used to group logically related data?

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• Avoiding bloated Domain Objects

  - by djcredo

  We're trying to move data from our bloated Service layer into our Domain layer using a DDD approach. We currently have a lot of business logic in our services, which is spread out all over the place and doesn't benefit from inheritance. We have a central Domain class which is the focus of most of our work - a Trade. The Trade object will know how to price itself, how to estimate risk, validate itself, etc. We can then replace conditionals with polymorphism. Eg: SimpleTrade will price itself one way, but ComplexTrade will price itself another. However, we are worried that this will bloat the Trade class(s). It really should be in charge of its own processing but the class size is going to increase exponentially as more features are added. So we have choices: Put processing logic in Trade class. Processing logic is now polymorphic based on the type of the trade, but Trade class is now has multiple responsibilites (pricing, risk, etc) and is large Put processing logic into other class such as TradePricingService. No longer polymorphic with the Trade inheritance tree, but classes are smaller and easier to test. What would be the suggested approach?

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• Domain Model and Querying

  - by Tyrsius

  I am new to DDD, having worked only in Transaction-Script apps with an anemic model, or just Big Balls of Mud, so please forgive any terminology I abuse. I am trying to understand the proper separation between the domain model and the repository. What is the proper way to construct a domain object that is coming from a database, assuming the (incredibly simplified) need to query for objects by status (returns enumerable), or by ID. Should a factory be building the objects, exposing methods for GetByStatus() and GetByID(), using a DIed repository? Should a repository be called directly, knowing how to build a domain model from the DTO? Should the domain model have a constructor for get by ID, using a DIed repoistory to load the initial state, using some other (?) method for the list? I am not really sure what the best way would be, and this question has an answer advocating each one (these are certainly mutuallu exclusive).

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• How to decide to which class does a method belong

  - by Eleeist

  I have TopicBusiness.class and PostBusiness.class. I have no problem with deciding into which class methods such as addPostToDatabase() or getAllPostsFromDatabase() should go. But what about getAllPostsFromTopic(TopicEntity topic) or getNumberOfPostsInTopic(TopicEntity topic)? Should the parameter be the deciding factor? So when the method takes TopicEntity as parameter it should belong to TopicBusiness.class? I am quite puzzled by this.

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• Is this a violation of the Liskov Substitution Principle?

  - by Paul T Davies

  Say we have a list of Task entities, and a ProjectTask sub type. Tasks can be closed at any time, except ProjectTasks which cannot be closed once they have a status of Started. The UI should ensure the option to close a started ProjectTask is never available, but some safeguards are present in the domain: public class Task { public Status Status { get; set; } public virtual void Close() { Status = Status.Closed; } } public ProjectTask : Task { public override void Close() { if (Status == Status.Started) throw new Exception("Cannot close a started Project Task"); base.Close(); } } Now when calling Close() on a Task, there is a chance the call will fail if it is a ProjectTask with the started status, when it wouldn't if it was a base Task. But this is the business requirements. It should fail. Can this be regarded as a violation?

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• Random generation of interesting puzzle levels?

  - by monsterfarm

  I'm making a Sokoban-like game i.e. there's a grid that has some crates on it you can push and you have to get the crates on crosses to win the level (although I'm going to add some extra elements to it). Are there any general algorithms or reading material I can look at for how I could go about generating interesting (as in, not trivial to solve) levels for this style of game? I'm aware that random level generators exist for Sokoban but I'm having trouble finding the algorithm descriptions. I'm interested in making a game where the machine can generate lots of levels for me, sorted by difficulty. I'm even willing to constrain the rules of the game to make the level generation easier (e.g. I'll probably limit the grid size to about 7x7). I suspect there are some general ways to do level generation here as I've seen e.g. Traffic Jam-like games (where you have to move blocks around the free some block) with 1000s of levels where each one has a unique solution. One idea I had was to generate a random map in its final state (i.e. where all crates are on top of their crosses) and then the computer would pull (instead of push) these crates around to create a level. The nice property here is that we know the level is solvable. However, I'd need some heuristics to ensure the level was interesting.

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• Best approach for tracking dependent state

  - by Pace

  Let's pretend I work on a project tracking application. The application is a database backed, server hosted, web application. In this application there are Projects which have many Activities which have many Tasks. A Task has two date fields an originalDueDate and a projectedDueDate. In addition, there are dynamic fields on the Activities and the Projects which indicate whether the Activity or Project is behind schedule based on the projected due dates of the child tasks and various other variables such as remaining buffer time, etc. There are a number of things that can cause the projectedDueDate to change. For example, an employee working on the project may (via a server request) enter in a shipping delay. Alternatively, a site may (via a server request) enter in an unexpected closure. When any of these things occur I need to not only update the projectedDueDate of the Task but also trigger the corresponding Project and Activity to update as well. What is the best way to do this? I've thought of the observer pattern but I don't keep a single copy of all these objects in memory. When a request comes in, I query the Task in from the database, at that point there is no associated Activity in memory that would be a listener. I could remove the ability to query for Tasks and force the application to query first by Project, then by Activity (in context of Project), then by task (in context of Activity) adding the observer relationships at each step but I'm not sure if that is the best way. I could setup a database event listening system so when a Task modified event is dispatched I have a handler which queries for the Activity at that point. I could simply setup a two-way relationship between Task and Activity so that the Task knows about the parent Activity and when the Task updates his state the Task grabs his parent and updates state. Right now I'm stuck considering all the options and am wondering if any single approach (doesn't have to be a listed approach) is jumping out at others as the best approach.

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• How should I define my Java Objects?

  - by HonorGod

  I have a data grid where I sort of show the following information - All Guests Total Adults = 22 Total Children = 27 Confirmed Total Adults = 9 Total Children = 13 Country = Germany Total Adults = 5 Total Childres = 6 Friends Adults = 2 Children = 2 Relatives Adults = 3 Children = 4 Country = USA Total Adults = 4 Total Childres = 7 Friends Adults = 2 Children = 5 Relatives Adults = 2 Children = 2 Tentative Total Adults = 13 Total Children - 14 Country = Australia Total Adults = 7 Total Childres = 8 Friends Adults = 2 Children = 3 Relatives Adults = 5 Children = 5 Country = China Total Adults = 6 Total Childres = 6 Friends Adults = 2 Children = 4 Relatives Adults = 4 Children = 2 And in the database what I have is data at the lowest level which is Friends / Relatives and the corresponding countries set as a look-up value which in indirectly connected to another look-up that can tell me if they fall under confirmed or tentative. I guess my question is how do I layout my Java Object and perform the aggregations and give it back to the client. I am not sure if I am clear with my question, but feel free to comment so I can update the question accordingly.

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