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  • Should I forward the a call to .Equals onto .Equals<T>?

    - by Jaimal Chohan
    So, I've got you bog standard c# object, overriding Equalsand implementing IEquatable public override int GetHashCode() { return _name.GetHashCode(); } public override bool Equals(object obj) { return Equals(obj as Tag) } #region IEquatable<Tag> Members public bool Equals(Tag other) { if (other == null) return false; else return _name == other._name; } #endregion Now, for some reason, I used to think that forwarding the calls from Equals into Equals was bad, no idea why, perhaps I read it a long time ago, anyway I'd write separate (but logically same) code for each method. Now I think forwarding Equals to Equals is okay, for obvious reasons, but for the life me I can't remember why I thought it wasn't before. Any thoughts?

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  • Code to simulate a users actions, such as logging in

    - by Gortron
    I've recently begun working on a PHP application, replacing another developer. I believed the application was using an API to communicate with a remote service but when I looked through the code I found that it was using a set of functions to actually log in, fill out forms and submit them as a user might do in a browser. My intention is to replace this code, to use the services API instead. I've considered leaving the code as is and not replace it. It makes me wonder though is this a common practice in the software industry? To have a programme simulate a users actions in a browser to perform a set of actions? It feels to me that this is clever but poor programming, Have any other developers seen this?

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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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  • What are your worst experiences with whitespace?

    - by CheeseConQueso
    What are some good examples of whitespace being the cause of any type of error and/or total disruption of scripts and/or markups? I am more interested in any accounts related to languages that are used commonly today, but I would like to hear about any cases in general. PS - This should be a wiki, but I don't know what happened to the "make this a wiki" check box. If someone comes across this with the rights to set it as a "wiki", please do so. If SO decided they wanted to keep away from wiki's altogether, please comment me about that. Thanks

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  • Do you leverage the benefits of the open-closed principle?

    - by Kaleb Pederson
    The open-closed principle (OCP) states that an object should be open for extension but closed for modification. I believe I understand it and use it in conjunction with SRP to create classes that do only one thing. And, I try to create many small methods that make it possible to extract out all the behavior controls into methods that may be extended or overridden in some subclass. Thus, I end up with classes that have many extension points, be it through: dependency injection and composition, events, delegation, etc. Consider the following a simple, extendable class: class PaycheckCalculator { // ... protected decimal GetOvertimeFactor() { return 2.0M; } } Now say, for example, that the OvertimeFactor changes to 1.5. Since the above class was designed to be extended, I can easily subclass and return a different OvertimeFactor. But... despite the class being designed for extension and adhering to OCP, I'll modify the single method in question, rather than subclassing and overridding the method in question and then re-wiring my objects in my IoC container. As a result I've violated part of what OCP attempts to accomplish. It feels like I'm just being lazy because the above is a bit easier. Am I misunderstanding OCP? Should I really be doing something different? Do you leverage the benefits of OCP differently? Update: based on the answers it looks like this contrived example is a poor one for a number of different reasons. The main intent of the example was to demonstrate that the class was designed to be extended by providing methods that when overridden would alter the behavior of public methods without the need for changing internal or private code. Still, I definitely misunderstood OCP.

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  • How to organize a Coding Dojo?

    - by Stephan
    Over on stack overflow it was asked how to organize a coding dojo (http://stackoverflow.com/questions/4338567/how-to-organize-a-coding-dojo-event). I believe that may have been the wrong forum... I wonder the same thing: how is a Codeing Dojo organized? What is the structure of a meeting? How would one pick Katas? What do you plan ahead of time? I am interested in any ideas on this as well as links to any resource that may be outlining this.

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  • Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

    - by Rowan Freeman
    Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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  • How to implement child-parent aggregation link in C++?

    - by Giorgio
    Suppose that I have three classes P, C1, C2, composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed. an association relation between instances of C1 and C2 (not necessarily between children of the same P). To implement this, in C++ I normally define three classes P, C1, C2, define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor, implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established. Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this? My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like: class C1 { public: C1(P * const p, ...) : paren(p) { ... } private: P * const parent; ... }; class P { public: P(...) : childC1(new C1(this, ...)) ... { ... } private: boost::shared_ptr<C1> childC1; ... }; Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.

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  • How often is seq used in Haskell production code?

    - by Giorgio
    I have some experience writing small tools in Haskell and I find it very intuitive to use, especially for writing filters (using interact) that process their standard input and pipe it to standard output. Recently I tried to use one such filter on a file that was about 10 times larger than usual and I got a Stack space overflow error. After doing some reading (e.g. here and here) I have identified two guidelines to save stack space (experienced Haskellers, please correct me if I write something that is not correct): Avoid recursive function calls that are not tail-recursive (this is valid for all functional languages that support tail-call optimization). Introduce seq to force early evaluation of sub-expressions so that expressions do not grow to large before they are reduced (this is specific to Haskell, or at least to languages using lazy evaluation). After introducing five or six seq calls in my code my tool runs smoothly again (also on the larger data). However, I find the original code was a bit more readable. Since I am not an experienced Haskell programmer I wanted to ask if introducing seq in this way is a common practice, and how often one will normally see seq in Haskell production code. Or are there any techniques that allow to avoid using seq too often and still use little stack space?

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  • Building a template engine - starting point

    - by Anirudh
    We're building a Django-based project with a template component. This component will be separate from the project as such and can be Django/Python, Node, Java or whatever works. The template has to be rendered into HTML. The templates will contain references to objects with properties that are defined in the DB, say, a Bus. For eg, it could be something like [object type="vehicle" weight="heavy"] and it would have to pull a random object from the DB fulfilling the criteria : type="vehicle" weight="heavy" (bus/truck/jet) and then substitute that tag with an image, say, of a Bus. Also it would have to be able to handle some processing. Eg: What is [X type="integer" lte="10"] + [Y type="integer" lte="10"] [option X+Y correct_ans="true"] [option X-Y correct_ans="false"] [option X+y+1 correct_ans="false"] The engine would be expected to fill in a random integer value <= 10 for X and Y and show radioboxes for each of the options. Would also have to store the fact that the first option is the correct answer. Does it to make sense to write something from the scratch? Or is it better to use an existing templating system (like Django's own templating system) as a starting point? Any suggestions on how I can approach this?

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  • Is there a good design pattern for this messaging class?

    - by salonMonsters
    Is there a good design pattern for this? I want to create a messaging class. The class will be passed: the type of message (eg. signup, signup confirmation, password reminder etc) the client's id The class needs to then look up the client's messaging preferences in the db (whether they want communication by email, sms or both) Then depending on the client's preference it will format the message for the medium (short version for sms, long form for email) and send it through our mail or sms provider's API. Because the fact that we want to be able to change out email and sms providers if need be I wondered if the Command Pattern would be a good choice.

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  • What is a good design pattern / lib for iOS 5 to synchronize with a web service?

    - by Junto
    We are developing an iOS application that needs to synchronize with a remote server using web services. The existing web services have an "operations" style rather than REST (implemented in WCF but exposing JSON HTTP endpoints). We are unsure of how to structure the web services to best fit with iOS and would love some advice. We are also interested in how to manage the synchronization process within iOS. Without going into detailed specifics, the application allows the user to estimate repair costs at a remote site. These costs are broken down by room and item. If the user has an internet connection this data can be sent back to the server. Multiple photographs can be taken of each item, but they will be held in a separate queue, which sends when the connection is optimal (ideally wifi). Our backend application controls the unique ids for each room and item. Thus, each time we send these costs to the server, the server echoes the central database ids back, thus, that they can be synchronized in the mobile app. I have simplified this a little, since the operations contract is actually much larger, but I just want to illustrate the basic requirements without complicating matters. Firstly, the web service architecture: We currently have two operations: GetCosts and UpdateCosts. My assumption is that if we used a strict REST architecture we would need to break our single web service operations into multiple smaller services. This would make the services much more chatty and we would also have to guarantee a delivery order from the app. For example, we need to make sure that containing rooms are added before the item. Although this seems much more RESTful, our perception is that these extra calls are expensive connections (security checks, database calls, etc). Does the type of web api (operation over service focus) determine chunky vs chatty? Since this is mobile (3G), are we better handling lots of smaller messages, or a few large ones? Secondly, the iOS side. What is the current advice on how to manage data synchronization within the iOS (5) app itself. We need multiple queues and we need to guarantee delivery order in each queue (and technically, ordering between queues). The server needs to control unique ids and other properties and echo them back to the application. The application then needs to update an internal database and when re-updating, make sure the correct ids are available in the update message (essentially multiple inserts and updates in one call). Our backend has a ton of business logic operating on these cost estimates. We don't want any of this in the app itself. Currently the iOS app sends the cost data, and then the server echoes that data back with populated ids (and other data). The existing cost data is deleted and the echoed response data is added to the client database on the device. This is causing us problems, because any photos might not have been sent, but the original entity tree has been removed and replaced. Obviously updating the costs tree rather than replacing it would remove this problem, but I'm not sure if there are any nice xcode libraries out there to do such things. I welcome any advice you might have.

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  • How essential is it to make a service layer?

    - by BornToCode
    I started building an app in 3 layers (DAL, BL, UI) [it mainly handles CRM, some sales reports and inventory]. A colleague told me that I must move to service layer pattern, that developers came to service pattern from their experience and it is the better approach to design most applications. He said it would be much easier to maintain the application in the future that way. Personally, I get the feeling that it's just making things more complex and I couldn't see much of a benefit from it that would justify that. This app does have an additional small partial ui that uses some (but only few) of the desktop application functions so I did find myself duplicating some code (but not much). Just because of some code duplication I wouldn't convert it to be service oriented, but he said I should use it anyway because in general it's a very good architecture, why programmers are so in love with services?? I tried to google on it but I'm still confused and can't decide what to do.

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  • Is it bad to be the only person supporting software you have developed?

    - by trpt4him
    My employer has a need for a web-based application to manage and share data within the department, with approximately 50-75 possible users. I feel I have the ability to write it for them. I would likely use Python/Django with a MySQL database, so it would be open source. However, I'm the only IT person in my department (our larger organization has a separate IT support staff with which I often work, but not for web development). I want to develop this application, but if I leave in 1-2 years, and someone else has to come in after me and support it, will this be seen as a bad decision? This is assuming all the obvious points -- I will write documentation, I will comment my code, and I will strive to follow good application design principles. But will that be enough? In principle, is it acceptable for one person to develop and support an entire web application? Is this a "do first, then show and ask" kind of situation, or should I be certain it will be adopted by everyone involved first?

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  • In MVC , DAO should be called from Controller or Model

    - by tito
    I have seen various arguments against the DAO being called from the Controller class directly and also the DAO from the Model class.Infact I personally feel that if we are following the MVC pattern , the controller should not coupled with the DAO , but the Model class should invoke the DAO from within and controller should invoke the model class.Why because , we can decouple the model class apart from a webapplication and expose the functionalities for various ways like for a REST service to use our model class. If we write the DAO invocation in the controller , it would not be possible for a REST service to reuse the functionality right ? I have summarized both the approaches below. Approach #1 public class CustomerController extends HttpServlet { proctected void doPost(....) { Customer customer = new Customer("xxxxx","23",1); new CustomerDAO().save(customer); } } Approach #2 public class CustomerController extends HttpServlet { proctected void doPost(....) { Customer customer = new Customer("xxxxx","23",1); customer.save(customer); } } public class Customer { ........... private void save(Customer customer){ new CustomerDAO().save(customer); } } Note- Here is what a definition of Model is : Model: The model manages the behavior and data of the application domain, responds to requests for information about its state (usually from the view), and responds to instructions to change state (usually from the controller). In event-driven systems, the model notifies observers (usually views) when the information changes so that they can react. I would need an expert opinion on this because I find many using #1 or #2 , So which one is it ?

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  • How can i manage my personal notes , code snippets files in one place online [closed]

    - by user1758043
    Whenever i work on any project , then i have so much notes , diagrams files , image s, brainstorming ideas which i want to keep. i want to put them in one place so that i can see the history of my work. Is there any toll whichere i can store this online. my company is using confluence but thats costly for me. I want something for single user but online in clou where i can store Notes Code snippets Diagrams , flowchart Attah files , images Books marks , sites

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  • Dealing with curly brace soup

    - by Cyborgx37
    I've programmed in both C# and VB.NET for years, but primarily in VB. I'm making a career shift toward C# and, overall, I like C# better. One issue I'm having, though, is curly brace soup. In VB, each structure keyword has a matching close keyword, for example: Namespace ... Class ... Function ... For ... Using ... If ... ... End If If ... ... End If End Using Next End Function End Class End Namespace The same code written in C# ends up very hard to read: namespace ... { class ... { function ... { for ... { using ... { if ... { ... } if ... { ... } } } // wait... what level is this? } } } Being so used to VB, I'm wondering if there's a technique employed by c-style programmers to improve readability and to ensure that your code ends up in the correct "block". The above example is relatively easy to read, but sometimes at the end of a piece of code I'll have 8 or more levels of curly braces, requiring me to scroll up several pages to figure out which brace ends the block I'm interested in.

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  • Is the "One Description Table to rule them all" approch good?

    - by DavRob60
    Long ago, I worked (as a client) with a software which use a centralized table for it's codified element. Here, as far as I remember, how the table look like : Table_Name (PK) Field_Name (PK) Code (PK) Sort_Order Description So, instead of creating a table every time they need a codified field, they where just adding row in this table with the new Table_Name and Field_Name. I'm sometime tempted to use this pattern in some database I design, but I have resisted to this as from now, I think there's something wrong with this, but I cannot put the finger on it. It is just because you land with some of the structure logic within the Data or something else?

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  • Let your Signature Experience drive IT-decision making

    - by Tania Le Voi
    Today’s CIO job description:  ‘’Align IT infrastructure and solutions with business goals and objectives ; AND while doing so reduce costs; BUT ALSO, be innovative, ensure the architectures are adaptable and agile as we need to act today on the changes that we may request tomorrow.”   Sound like an unachievable request? The fact is, reality dictates that CIO’s are put under this type of pressure to deliver more with less. In a past career phase I spent a few years as an IT Relationship Manager for a large Insurance company. This is a role that we see all too infrequently in many of our customers, and it’s a shame.  The purpose of this role was to build a bridge, a relationship between IT and the business. Key to achieving that goal was to ensure the same language was being spoken and more importantly that objectives were commonly understood - hence service and projects were delivered to time, to budget and actually solved the business problems. In reality IT and the business are already married, but the relationship is most often defined as ‘supplier’ of IT rather than a ‘trusted partner’. To deliver business value they need to understand how to work together effectively to attain this next level of partnership. The Business cannot compete if they do not get a new product to market ahead of the competition, or for example act in a timely manner to address a new industry problem such as a legislative change. An even better example is when the Application or Service fails and the Business takes a hit by bad publicity, being trending topics on social media and losing direct revenue from online channels. For this reason alone Business and IT need the alignment of their priorities and deliverables now more than ever! Take a look at Forrester’s recent study that found ‘many IT respondents considering themselves to be trusted partners of the business but their efforts are impaired by the inadequacy of tools and organizations’.  IT Meet the Business; Business Meet IT So what is going on? We talk about aligning the business with IT but the reality is it’s difficult to do. Like any relationship each side has different goals and needs and language can be a barrier; business vs. technology jargon! What if we could translate the needs of both sides into actionable information, backed by data both sides understand, presented in a meaningful way?  Well now we can with the Business-Driven Application Management capabilities in Oracle Enterprise Manager 12cR2! Enterprise Manager’s Business-Driven Application Management capabilities provide the information that IT needs to understand the impact of its decisions on business criteria.  No longer does IT need to be focused solely on speeds and feeds, performance and throughput – now IT can understand IT’s impact on business KPIs like inventory turns, order-to-cash cycle, pipeline-to-forecast, and similar.  Similarly, now the line of business can understand which IT services are most critical for the KPIs they care about. There are a good deal of resources on Oracle Technology Network that describe the functionality of these products, so I won’t’ rehash them here.  What I want to talk about is what you do with these products. What’s next after we meet? Where do you start? Step 1:  Identify the Signature Experience. This is THE business process (or set of processes) that is core to the business, the one that drives the economic engine, the process that a customer recognises the company brand for, reputation, the customer experience, the process that a CEO would state as his number one priority. The crème de la crème of your business! Once you have nailed this it gets easy as Enterprise Manager 12c makes it easy. Step 2:  Map the Signature Experience to underlying IT.  Taking the signature experience, map out the touch points of the components that play a part in ensuring this business transaction is successful end to end, think of it like mapping out a critical path; the applications, middleware, databases and hardware. Use the wealth of Enterprise Manager features such as Systems, Services, Business Application Targets and Business Transaction Management (BTM) to assist you. Adding Real User Experience Insight (RUEI) into the mix will make the end to end customer satisfaction story transparent. Work with the business and define meaningful key performance indicators (KPI’s) and thresholds to enable you to report and action upon. Step 3:  Observe the data over time.  You now have meaningful insight into every step enabling your signature experience and you understand the implication of that experience on your underlying IT.  Watch if for a few months, see what happens and reconvene with your business stakeholders and set clear and measurable targets which can re-define service levels.  Step 4:  Change the information about which you and the business communicate.  It’s amazing what happens when you and the business speak the same language.  You’ll be able to make more informed business and IT decisions. From here IT can identify where/how budget is spent whether on the level of support, performance, capacity, HA, DR, certification etc. IT SLA’s no longer need be focused on metrics such as %availability but structured around business process requirements. The power of this way of thinking doesn’t end here. IT staff get to see and understand how their own role contributes to the business making them accountable for the business service. Take a step further and appraise your staff on the business competencies that are linked to the service availability. For the business, the language barrier is removed by producing targeted reports on the signature experience core to the business and therefore key to the CEO. Chargeback or show back becomes easier to justify as the ‘cost of day per outage’ can be more easily calculated; the business will be able to translate the cost to the business to the cost/value of the underlying IT that supports it. Used this way, Oracle Enterprise Manager 12c is a key enabler to a harmonious relationship between the end customer the business and IT to deliver ultimate service and satisfaction. Just engage with the business upfront, make the signature experience visible and let Enterprise Manager 12c do the rest. In the next blog entry we will cover some of the Enterprise Manager features mentioned to enable you to implement this new way of working.  

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  • How to refactor my design, if it seems to require multiple inheritance?

    - by Omega
    Recently I made a question about Java classes implementing methods from two sources (kinda like multiple inheritance). However, it was pointed out that this sort of need may be a sign of a design flaw. Hence, it is probably better to address my current design rather than trying to simulate multiple inheritance. Before tackling the actual problem, some background info about a particular mechanic in this framework: It is a simple game development framework. Several components allocate some memory (like pixel data), and it is necessary to get rid of it as soon as you don't need it. Sprites are an example of this. Anyway, I decided to implement something ala Manual-Reference-Counting from Objective-C. Certain classes, like Sprites, contain an internal counter, which is increased when you call retain(), and decreased on release(). Thus the Resource abstract class was created. Any subclass of this will obtain the retain() and release() implementations for free. When its count hits 0 (nobody is using this class), it will call the destroy() method. The subclass needs only to implement destroy(). This is because I don't want to rely on the Garbage Collector to get rid of unused pixel data. Game objects are all subclasses of the Node class - which is the main construction block, as it provides info such as position, size, rotation, etc. See, two classes are used often in my game. Sprites and Labels. Ah... but wait. Sprites contain pixel data, remember? And as such, they need to extend Resource. But this, of course, can't be done. Sprites ARE nodes, hence they must subclass Node. But heck, they are resources too. Why not making Resource an interface? Because I'd have to re-implement retain() and release(). I am avoiding this in virtue of not writing the same code over and over (remember that there are multiple classes that need this memory-management system). Why not composition? Because I'd still have to implement methods in Sprite (and similar classes) that essentially call the methods of Resource. I'd still be writing the same code over and over! What is your advice in this situation, then?

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  • Are first-class functions a substitute for the Strategy pattern?

    - by Prog
    The Strategy design pattern is often regarded as a substitute for first-class functions in languages that lack them. So for example say you wanted to pass functionality into an object. In Java you'd have to pass in the object another object which encapsulates the desired behavior. In a language such as Ruby, you'd just pass the functionality itself in the form of an annonymous function. However I was thinking about it and decided that maybe Strategy offers more than a plain annonymous function does. This is because an object can hold state that exists independently of the period when it's method runs. However an annonymous function by itself can only hold state that ceases to exist the moment the function finishes execution. So my question is: when using a language that features first-class functions, would you ever use the Strategy pattern (i.e. encapsulate the functionality you want to pass around in an explicit object), or would you always use an annonymous function? When would you decide to use Strategy when you can use a first-class function?

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  • How bad is it to have two methods with the same name but different signatures in two classes?

    - by Super User
    I have a design problem related to a public interface, the names of methods, and the understanding of my API and code. I have two classes like this: class A: ... function collision(self): .... ... class B: .... function _collision(self, another_object, l, r, t, b): .... The first class has one public method named collision, and the second has one private method called _collision. The two methods differs in argument type and number. As an example let's say that _collision checks if the object is colliding with another object with certain conditions l, r, t, b (collide on the left side, right side, etc) and returns true or false. The public collision method, on the other hand, resolves all the collisions of the object with other objects. The two methods have the same name because I think it's better to avoid overloading the design with different names for methods that do almost the same thing, but in distinct contexts and classes. Is this clear enough to the reader or I should change the method's name?

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  • Making Modular, Reusable and Loosely Coupled MVC Components

    - by Dusan
    I am building MVC3 application and need some general guidelines on how to manage complex client side interaction between my components. Here is my definition of one component in general way: Component which has it's own controller, model and view. All of the component's logic is placed inside these three parts and component is sort of "standalone", it contains it's own form, data needed for interaction, updates itself with Ajax and so on. Beside this internal logic and behavior of the component, it needs to be able to "Talk" to the outside world. By this I mean it should provide data and events (sort of) so when this component gets embedded in pages can notify other components which then can update based on the current state and data. I have an idea to use client ViewModel (in java-script) which would hookup all relevant components on page and control interaction between them. This would make components reusable, modular - independent of the context in which they are used. How would you do this, I am a bit stuck as I do not know if this is a good approach and there is a technical possibility to achieve this using java-script/jquery. The confusing part is about update via Ajax, how to ensure that component is properly linked to ViewModel when component is Ajax updated (or even worse removed or dynamically added). Also, how should this ViewModel be constructed and which technicalities to use here and in components to work as synergy??? On the web, I have found the various examples of the similar approach, but they are oversimplified (even for dummies) or over specific and do not provide valuable resource or general solution for this kind of implementation. If you have some serious examples it would be, also, very helpful. Note: My aim is to make interactions between many components on the same page simpler and more robust and elegant.

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  • What should a domain object's validation cover?

    - by MarcoR88
    I'm trying to figure out how to do validation of domain objects that need external resources, such as data mappers/dao Firstly here's my code class User { const INVALID_ID = 1; const INVALID_NAME = 2; const INVALID_EMAIL = 4; int getID(); void setID(Int i); string getName(); void setName(String s); string getEmail(); void setEmail(String s); int getErrorsForInsert(); // returns a bitmask for INVALID_* constants int getErrorsForUpdate(); } My worries are about the uniqueness of the email, checking it would require the storage layer. Reading others' code seems that two solutions are equally accepted: both perform the unique validation in data mapper but some set an error state to the DO user.addError(User.INVALID_EMAIL) while others prefer to throw a totally different type of exception that covers only persistence, like: UserStorageException { const INVALID_EMAIL = 1; const INVALID_CITY = 2; } What are the pros and cons of these solutions?

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  • How to implment the database for event conditions and item bonuses for a browser based game

    - by Saifis
    I am currently creating a browser based game, and was wondering what was the standard approach in making diverse conditions and status bonuses database wise. Currently considering two cases. Event Conditions Needs min 1000 gold Needs min Lv 10 Needs certain item. Needs fulfillment of another event Status Bonus Reduces damage by 20% +100 attack points Deflects certain type of attack I wish to be able to continually change these parameters during the process of production and operation, so having them hard-coded isn't the best way. All I could come up with are the following two methods. Method 1 Create a table that contains each conditions with needed attributes Have a model named conditions with all the attributes it would need to set them conditions condition_type (level, money_min, money_max item, event_aquired) condition_amount prerequisite_condition_id prerequisite_item_id Method 2 write it in a DSL form that could be interpreted later in the code Perhaps something like yaml, have a text area in the setting form and have the code interpret it. condition_foo: condition_type :level min_level: 10 condition_type :item item_id: 2 At current Method 2 looks to be more practical and flexible for future changes, trade off being that all the flex must be done on the code side. Not to sure how this is supposed to be done, is it supposed to be hard coded? separate config file? Any help would be appreciated. Added For additional info, it will be implemented with Ruby on Rails

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