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  • MVC pattern implementation. What is the n-relation between its components

    - by Srodriguez
    Dear all, I'm working in a C# project and we are , in order to get some unity across the different parts of our UI, trying to use the MVC pattern. The client is windows form based and I'm trying to create a simple MVC pattern implementation. It's been more challenging than expected, but I still have some questions regarding the MVC pattern. The problem comes mostly from the n-n relationships between its components: Here is what I've understood, but I'm not sure at all of it. Maybe someone can correct me? Model: can be shared among different Views. 1-n relationship between Model-View View: shows the state of the model. only one controller (can be shared among different views?). 1-1 relationship with the Model, 1-1 relationship with the controller Controller: handles the user actions on the view and updates the model. One controller can be shared among different views, a controller interacts only with one model? I'm not sure about the two last ones: Can a view have several controller? Or can a view share a controller with another view? Or is it only a 1:1 relationship? Can a controller handle several views? can it interact with several models? Also, I take advantage of this question to ask another MVC related question. I've suppressed all the synchronous calls between the different members of the MVC, making use of the events and delegates. One last call is still synchronous and is actually the most important one: The call between the view and the controller is still synchronous, as I need to know rather the controller has been able to handle the user's action or not. This is very bad as it means that I could block the UI thread (hence the client itself) while the controller is processing or doing some work. How can I avoid this? I can make use of the callback but then how do i know to which event the callback comes from? PS: I can't change the pattern at this stage, so please avoid answers of type "use MVP or MVVC, etc ;) Thanks!

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  • MVC pattern implementation. What is the n-relation between its components

    - by Srodriguez
    Dear all, I'm working in a C# project and we are , in order to get some unity across the different parts of our UI, trying to use the MVC pattern. The client is windows form based and I'm trying to create a simple MVC pattern implementation. It's been more challenging than expected, but I still have some questions regarding the MVC pattern. The problem comes mostly from the n-n relationships between its components: Here is what I've understood, but I'm not sure at all of it. Maybe someone can correct me? Model: can be shared among different Views. 1-n relationship between Model-View View: shows the state of the model. only one controller (can be shared among different views?). 1-1 relationship with the Model, 1-1 relationship with the controller Controller: handles the user actions on the view and updates the model. One controller can be shared among different views, a controller interacts only with one model? I'm not sure about the two last ones: Can a view have several controller? Or can a view share a controller with another view? Or is it only a 1:1 relationship? Can a controller handle several views? can it interact with several models? Also, I take advantage of this question to ask another MVC related question. I've suppressed all the synchronous calls between the different members of the MVC, making use of the events and delegates. One last call is still synchronous and is actually the most important one: The call between the view and the controller is still synchronous, as I need to know rather the controller has been able to handle the user's action or not. This is very bad as it means that I could block the UI thread (hence the client itself) while the controller is processing or doing some work. How can I avoid this? I can make use of the callback but then how do i know to which event the callback comes from? PS: I can't change the pattern at this stage, so please avoid answers of type "use MVP or MVVC, etc ;) Thanks!

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  • Delegates in Action -Help

    - by Amutha
    I am learning delegates.I am very curious to apply delegates to the following chain-of-responsibility pattern. Kindly help me the way to apply delegates to the following piece. Thanks in advance.Thanks for your effort. #region Chain of Responsibility Pattern namespace Chain { public class Player { public string Name { get; set; } public int Score { get; set; } } public abstract class PlayerHandler { protected PlayerHandler _Successor = null; public abstract void HandlePlayer(Player _player); public void SetupHandler(PlayerHandler _handler) { _Successor = _handler; } } public class Employee : PlayerHandler { public override void HandlePlayer(Player _player) { if (_player.Score <= 100) { MessageBox.Show(string.Format("{0} is greeted by Employee", _player.Name)); } else { _Successor.HandlePlayer(_player); } } } public class Supervisor : PlayerHandler { public override void HandlePlayer(Player _player) { if (_player.Score >100 && _player.Score<=200) { MessageBox.Show(string.Format("{0} is greeted by Supervisor", _player.Name)); } else { _Successor.HandlePlayer(_player); } } } public class Manager : PlayerHandler { public override void HandlePlayer(Player _player) { if (_player.Score > 200) { MessageBox.Show(string.Format("{0} is greeted by Manager", _player.Name)); } else { MessageBox.Show(string.Format("{0} got low score", _player.Name)); } } } } #endregion #region Main() void Main() { Chain.Player p1 = new Chain.Player(); p1.Name = "Jon"; p1.Score = 100; Chain.Player p2 = new Chain.Player(); p2.Name = "William"; p2.Score = 170; Chain.Player p3 = new Chain.Player(); p3.Name = "Robert"; p3.Score = 300; Chain.Employee emp = new Chain.Employee(); Chain.Manager mgr = new Chain.Manager(); Chain.Supervisor sup = new Chain.Supervisor(); emp.SetupHandler(sup); sup.SetupHandler(mgr); emp.HandlePlayer(p1); emp.HandlePlayer(p2); emp.HandlePlayer(p3); } #endregion

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  • How to keep historic details of modification in a database (Audit trail)?

    - by mada
    I'm a J2EE developer & we are using hibernate mapping with a PostgreSQL database. We have to keep track of any changes occurs in the database, in others words all previous & current values of any field should be saved. Each field can be any type (bytea, int, char...) With a simple table it is easy but we a graph of objects things are more difficult. So we have, speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that?

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  • How should i organize authority code?

    - by acidzombie24
    I have users that fall into the following Not logged in Not Verified Verified Moderator Admin All code that only admin and moderators can access (like banning) is in ModeratorUser which inherits from verified which inherits from BaseUser. Some pages are accessible to all users such as public profiles. If a user is logged in he can leave a comment. To check this i use if (IsVerifiedUser). Now here is the problem. To avoid problems if a user is banned he is not recognized as a verified user. However in the rare case i need to know if he is verified i can use usertype & Verified. Should i not be doing this? I have a bunch of code in my VerifiedUser class and find i am moving tons of it to BaseUser. Is this something i help because a not logged in user can access the page? Should i handle the ban user in a different way and allow IsVerifiedUser to be true even if the user is banned?

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  • Tips on designing a .NET API for future use with F#

    - by Drew Noakes
    I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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  • Immutability of big objects

    - by Malax
    Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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  • Are these jobs for developer or designers or for client itself? for a web-site projects

    - by jitendra
    Spell checking grammar checking Descriptive alt text for big chart , graph images, technical images To write Table summary and caption Descriptive Link text Color Contrast checking Deciding in content what should be H2 ,H3, H4... and what should be <strong> or <span class="boldtext"> Meta Description and keywords for each pages Image compression To decide Filenames for images,PDf etc To decide Page's <title> for each page

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  • Any tips of how to handle hierarchical trees in relational model?

    - by George
    Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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  • Risking the exception anti-pattern.. with some modifications

    - by Sridhar Iyer
    Lets say that I have a library which runs 24x7 on certain machines. Even if the code is rock solid, a hardware fault can sooner or later trigger an exception. I would like to have some sort of failsafe in position for events like this. One approach would be to write wrapper functions that encapsulate each api a: returnCode=DEFAULT; try { returnCode=libraryAPI1(); } catch(...) { returnCode=BAD; } return returnCode; The caller of the library then restarts the whole thread, reinitializes the module if the returnCode is bad. Things CAN go horribly wrong. E.g. if the try block(or libraryAPI1()) had: func1(); char *x=malloc(1000); func2(); if func2() throws an exception, x will never be freed. On a similar vein, file corruption is a possible outcome. Could you please tell me what other things can possibly go wrong in this scenario?

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  • How should I use color in my application? Single, Theme, or Chaos?

    - by CodeSlave
    How should I be using color in my application? I have over a 100 different forms (windows) in my application, and the default windows grey seems like a bad choice to me. One school of thought says pick one neutral color, and use the same one everywhere. Another school of thought says pick a set of neutral colors, and use them same ones within a group of form (e.g., shipping screens might be light green, receiving screens light orange, user administration screens light blue, etc.). The final school of thought says make every form different. We've got millions of colors, why not use them? What should I do and why?

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  • Is it okay to use try catch inside finally?

    - by Hiral Lakdavala
    Hi, I am using a buffered writer and my code, closes the writer in the finally block. My code is like this. ........... BufferedWriter theBufferedWriter = null; try{ theBufferedWriter =..... .... ...... ..... } catch (IOException anException) { .... } finally { try { theBufferedWriter.close(); } catch (IOException anException) { anException.printStackTrace(); } } I have to use the try catch inside the clean up code in finally as theBufferedWriter might also throw an IOException. I do not want to throw this exception to the calling methos. Is it a good practice to use a try catch in finally? If not what is the alternative? Please suggest. Regards, Hiral

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  • Avoid loading unnecessary data from db into objects (web pages)

    - by GmGr
    Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • Method hiding with interfaces

    - by fearofawhackplanet
    interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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  • C#: How to inherit constructors?

    - by Ian Boyd
    Imagine a base class with many constructors and a virtual method public class Foo { ... public Foo() {...} public Foo(int i) {...} ... public virtual void SomethingElse() {...} ... } and now I want to create a descendant class that overrides the virtual method: public class Bar : Foo { public override void SomethingElse() {...} } And another descendant that does some more stuff: public class Bah : Bar { public void DoMoreStuff() {...} } Do I really have to copy all constructors from Foo into Bar and Bah? And then if I change a constructor signature in Foo, do I have to update it in Bar and Bah? Is there no way to inherit constructors? Is there no way to encourage code reuse?

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  • Singleton Pattern combine with a Decorator

    - by Mike
    Attached is a classic Decorator pattern. My question is how would you modify the below code so that you can wrap zero or one of each topping on to the Pizza Right now I can have a Pepporini - Sausage -- Pepporini -- Pizza class driving the total cost up to $10, charging twice for Pepporini. I don't think I want to use the Chain of Responsibility pattern as order does not matter and not all toppings are used? Thank you namespace PizzaDecorator { public interface IPizza { double CalculateCost(); } public class Pizza: IPizza { public Pizza() { } public double CalculateCost() { return 8.00; } } public abstract class Topping : IPizza { protected IPizza _pizzaItem; public Topping(IPizza pizzaItem) { this._pizzaItem = pizzaItem; } public abstract double CalculateCost(); } public class Pepporini : Topping { public Pepporini(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 0.50; } } public class Sausage : Topping { public Sausage(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 1.00; } } public class Onions : Topping { public Onions(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + .25; } } }

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  • smallest mysql type that accomodates single decimal

    - by donpal
    Database newbie here. I'm setting up a mysql table. One of the fields will accept a value in increment of a 0.5. e.g. 0.5, 1.0, 1.5, 2.0, .... 200.5, etc. I've tried int but it doesn't capture the decimals. `value` int(10), What would be the smallest type that can accommodate this value, considering it's only a single decimal. I also was considering that because the decimal will always be 0.5 if at all, I could store it in a separate boolean field? So I would have 2 fields instead. Is this a stupid or somewhat over complicated idea? I don't know if it really saves me any memory, and it might get slower now that I'm accessing 2 fields instead of 1 `value` int(10), `half` bool, //or something similar to boolean What are your suggestions guys? Is the first option better, and what's the smallest data type in that case that would get me the 0.5?

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  • Generalized plugable caching pattern?

    - by BCS
    Given that it's one of the hard things in computer science, does anyone know of a way to set up a plugable caching strategy? What I'm thinking of would allow me to write a program with minimal thought as to what needs to be cached (e.i. use some sort of boiler-plate, low/no cost pattern that compiles away to nothing anywhere I might want caching) and then when things are further along and I know where I need caching I can add it in without making invasive code changes. As an idea to the kind of solution I'm looking for; I'm working with the D programing language (but halfway sane C++ would be fine) and I like template.

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  • Code Contracts Vs. Object Initializers (.net 4.0)

    - by Mystagogue
    At face value, it would seem that object initializers present a problem for .net 4.0 "code contracts", where normally the invariant should be established by the time the object constructor is finished. Presumably, however, object-initializers require properties to be set after construction is complete. My question is if the invariants of "code contracts" are able to handle object initializers, "as if" the properties were set before the constructor completes? That would be very nice indeed!!

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  • Truly declarative language?

    - by gjvdkamp
    Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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  • What are the DB smells?

    - by Jonas Byström
    We all know 'code smells', but what are the fundamental 'database smells'? I'm a DB n00b, but I'll give an example of something that I find fishy. It seems to me like when I have to join 6-8 tables together to optimize our loading that we have a DB smell? Or would that be a pretty 'normal' database layout? (Sure, early optimization is the root of all evil, but this seems to me like early pessimisation, not to mention the cumbersomeness?)

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  • Data Modeling Help - Do I add another table, change existing table's usage, or something else?

    - by StackOverflowNewbie
    Assume I have the following tables and relationships: Person - Id (PK) - Name A Person can have 0 or more pets: Pet - Id (PK) - PersonId (FK) - Name A person can have 0 or more attributes (e.g. age, height, weight): PersonAttribute _ Id (PK) - PersonId (FK) - Name - Value PROBLEM: I need to represent pet attributes, too. As it turns out, these pet attributes are, in most cases, identical to the attributes of a person (e.g. a pet can have an age, height, and weight too). How do I represent pet attributes? Do I create a PetAttribute table? PetAttribute Id (PK) PetId (FK) Name Value Do I change PersonAttribute to GenericAttribute and have 2 foreign keys in it - one connecting to Person, the other connecting to Pet? GenericAttribute Id (PK) PersonId (FK) PetId (FK) Name Value NOTE: if PersonId is set, then PetId is not set. If PetId is set, PersonId is not set. Do something else?

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