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• fluent nHibernate mapping of subclassed structure

  - by Codezy

  I have a workflow class that has a collection of phases, each phase has a collection of tasks. You can design a workflow that will be used by many engagements. When used in engagement I want to be able to add properties to each class (workflow, phase, and task). For example a task in the designer does not have people assigned, but a task in an engagement would need extra properties like who is assigned to it. I have tried many different approaches using subclasses or interfaces but I just can't get it to map the way I want. Currently I have the engagement level versions as subclasses, but I can't get Engagement phases to map to engagement workflows. Public Class WorkflowMapping Inherits ClassMap(Of Workflow) Sub New() Id(Function(x As Workflow) x.Id).Column("Workflow_Id").GeneratedBy.Identity() Map(Function(x As Workflow) x.Description) Map(Function(x As Workflow) x.Generation) Map(Function(x As Workflow) x.IsActive) HasMany(Function(x As Workflow) x.Phases).Cascade.All() End Sub End Class Public Class EngagementWorkflowMapping Inherits SubclassMap(Of EngagementWorkflow) Sub New() Map(Function(x As EngagementWorkflow) x.ClientNo) Map(Function(x As EngagementWorkflow) x.EngagementNo) End Sub End Class How would you approach mapping this in fluent (or hbm) so that you could load just the workflow base class when designing the flow, or the engagement subclass versions of each when being used by an engagement?

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• Generics with constraints hierarchy

  - by devoured elysium

  I am currently facing a very disturbing problem: interface IStateSpace<Position, Value> where Position : IPosition // <-- Problem starts here where Value : IValue // <-- and here as I don't { // know how to get away this // circular dependency! // Notice how I should be // defining generics parameters // here but I can't! Value GetStateAt(Position position); void SetStateAt(Position position, State state); } As you'll down here, both IPosition, IValue and IState depend on each other. How am I supposed to get away with this? I can't think of any other design that will circumvent this circular dependency and still describes exactly what I want to do! interface IState<StateSpace, Value> where StateSpace : IStateSpace where Value : IValue { StateSpace StateSpace { get; }; Value Value { get; set; } } interface IPosition { } interface IValue<State> where State : IState { State State { get; } } Basically I have a state space IStateSpace that has states IState inside. Their position in the state space is given by an IPosition. Each state then has one (or more) values IValue. I am simplifying the hierarchy, as it's a bit more complex than described. The idea of having this hierarchy defined with generics is to allow for different implementations of the same concepts (an IStateSpace will be implemented both as a matrix as an graph, etc). Would can I get away with this? How do you generally solve this kind of problems? Which kind of designs are used in these cases? Thanks

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• What is the equivalent of .NET events in Ruby?

  - by Gishu

  The problem is very simple. An object needs to notify some events that might be of interest to observers. When I sat to validate a design that I cooked up now in Ruby just to validate it.. I find myself stumped as to how to implement the object events. In .Net this would be a one-liner.. .Net also does handler method signature verification,etc. e.g. // Object with events public delegate void HandlerSignature(int a); public event HandlerSignature MyEvent; public event HandlerSignature AnotherCriticalEvent; // Client MyObject.MyEvent += new HandlerSignature(MyHandlerMethod); // MyHandlerMethod has same signature as delegate Is there an EventDispatcher module or something that I am missing that I can strap on to a Ruby class ? Hoping for an answer that plays along with Ruby's principle of least surprise. An event would be the name of the event plus a queue of [observer, methodName] objects that need to be invoked when the event takes place.

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• How to pass binary data between two apps using Content Provider?

  - by Viktor

  I need to pass some binary data between two android apps using Content Provider (sharedUserId is not an option). I would prefer not to pass the data (a savegame stored as a file, small in size < 20k) as a file (ie. overriding openFile()) since this would necessitate some complicated temp-file scheme to cope with concurrency with several content provider accesses and a running game. I would like to read the file into memory under a mutex lock and then pass the binary array in the simplest way possible. How do I do this? It seems creating a file in memory is not a possibility due to the return type of openFile(). query() needs to return a Cursor. Using MatrixCursor is not possible since it applies toString() to all stored objects when reading it. What do I need to do? Implement a custom Cursor? This class has 30 abstract methods. Do I read the file, put it in a SQLite db and return the cursor? The complexity of this seemingly simple task is mindboggling.

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• Aren't Information Expert / Tell Don't Ask at odds with Single Responsibility Principle?

  - by moffdub

  It is probably just me, which is why I'm asking the question. Information Expert, Tell Don't Ask, and SRP are often mentioned together as best practices. But I think they are at odds. Here is what I'm talking about: Code that favors SRP but violates Tell Don't Ask, Info Expert: Customer bob = ...; // TransferObjectFactory has to use Customer's accessors to do its work, // violates Tell Don't Ask CustomerDTO dto = TransferObjectFactory.createFrom(bob); Code that favors Tell Don't Ask / Info Expert but violates SRP: Customer bob = ...; // Now Customer is doing more than just representing the domain concept of Customer, // violates SRP CustomerDTO dto = bob.toDTO(); If they are indeed at odds, that's a vindication of my OCD. Otherwise, please fill me in on how these practices can co-exist peacefully. Thank you. Edit: someone wants a definition of the terms - Information Expert: objects that have the data needed for the operation should host the operation Tell Don't Ask: don't ask objects for data in order to do work; tell the objects to do the work Single Responsibility Principle: each object should have a narrowly defined responsibility

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• How do I use a modalViewController Identically in Two Controllers?

  - by Theory

  I'm using the Three20 TTMessageController in my app. I've figured out how to use it, adding on a bunch of other stuff (including TTMessageControllerDelegate methods and ABPeoplePickerNavigationControllerDelegate methods). It works great for me, after a bit of a struggle to figure it out. The trouble I'm having now is a design issue: I want to use it identically in two different places, including with the same delegate methods. My current approach is that I've put all the code into a single class inheriting from NSObject, called ComposerProxy, and I'm just having the two controllers that use it use the proxy, like so: ComposerProxy *proxy = [[ComposerProxy alloc] initWithController:this]; [proxy go]; The go method constructs the TTMessageController, configures it, adds it to a UINavigationController, and presents it: [self.controller presentModalViewController: navController animated: YES]; This works great, as I have all my code nicely encapsulated in ComposerProxy and I need only the above two lines anywhere I want to use it. The downside, though, is that I can't dealloc the proxy variable without getting crashes. I can't autorelease it, either: same problem. So I'm wondering if my proxy approach is a poor one. How does one normally encapsulate a bunch of behaviors like this without requiring a lot of duplicate code in the classes that use it? Do I need to add a delegate class to my ComposerProxy and make the controller responsible for dismissing the modal view controller in a hypothetical composerDidFinish method or some such? Many TIA!

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• How to have a policy class implement a virtual function?

  - by dehmann

  I'm trying to design a policy-based class, where a certain interface is implemented by the policy itself, so the class derives from the policy, which itself is a template (I got this kind of thinking from Alexandrescu's book): #include <iostream> #include <vector> class TestInterface { public: virtual void test() = 0; }; class TestImpl1 { public: void test() {std::cerr << "Impl1" << std::endl;} }; template<class TestPolicy> class Foo : public TestInterface, TestPolicy { }; Then, in the main() function, I call test() on (potentially) various different objects that all implement the same interface: int main() { std::vector<TestInterface*> foos; foos.push_back(new Foo<TestImpl1>()); foos[0]->test(); delete foos[0]; return 0; } It doesn't compile, though, because the following virtual functions are pure within ‘Foo<TestImpl1>’: virtual void TestInterface::test() I thought TestInterface::test() is implemented because we derive from TestImpl1?

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• What issues to consider when rolling your own data-backend for Silverlight / AJAX on non-ASP.NET ser

  - by Edward Tanguay

  I have read-only Silverlight and AJAX apps which read static text and XML files from a PHP/Apache server, which works very nicely with features such as asynchronous loading, lazy-loading only what I need for each page, loading in the background, developed a little query language to get a PHP script to create custom XML files etc. it's pragmatic read-only REST, and all works fast and fine for read-only sites. Now I want to also add the ability to write data from these apps to a database on the same PHP/Apache server. For those of you who have built similar data-access layers, what do I need to consider while building this, especially regarding security so that not just any client can write and alter my database, e.g.: check HTTP_USER_AGENT for security check REMOTE_ADDR for security require a special code for security, perhaps a list of TAN codes (such as banks use for online transactions) each which can only be used once, both the client and server have these I wonder if there is some kind of standard REST query I should lean on for e.g. building SQL-like statements in the URL parameters, e.g. http://www.thedatalayersite.com/query?insertinto=customers&... Any thoughts, notes from experience, ideas, gotchas, especially ideas on tightening down security in this endeavor would be helpful.

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• Can you have a Dynamic Data Field which consists of a list of fields?

  - by Telos

  This is a purely theoretical question (at least until I start trying to implement it) but here goes. I wrote a web form a long time ago which has a configurable section for getting information. Basically for some customers there are no fields, for other customers there are up to 20 fields. I got it working by dynamically creating the fields at just the right time in the page lifecycle and going through a lot of headaches. 2 years later, I need to make some pretty big updates to this web form and there are some nifty new technologies. I've worked with ASP.NET Dynamic Data just a bit and, well, I half-crazed plan just occurred to me: The Ticket object has a one-to-many relationship to ExtendedField, we'll call that relationship Fields for brevity. Using that, the idea would be to create a FieldTemplate that dynamically generated the list of fields and displayed it. The big questions here would probably be: 1) Can a single field template resolve to multiple web controls without breaking things? 2) Can dynamic data handle updating/inserting multiple rows in such a fashion? 3) There was a third question I had a few minutes ago, but coworkers interrupted me and I forgot. So now the third question is: what is the third question? So basically, does this sound like it could work or am I missing a better/more obvious solution?

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• How do I populate a MEF plugin with data that is not hard coded into the assembly?

  - by hjoelr

  I am working on a program that will communicate with various pieces of hardware. Because of the varied nature of the items it communicates and controls, I need to have a different "driver" for each different piece of hardware. This made me think that MEF would be a great way to make those drivers as plugins that can be added even after the product has been released. I've looked at a lot of examples of how to use MEF, but the question that I haven't been able to find an answer to is how to populate a MEF plugin with external data (eg. from a database). All the examples I can find have the "data" hard-coded into the assembly, like the following example: [Export( typeof( IRule ) )] public class RuleInstance : IRule { public void DoIt() {} public string Name { get { return "Rule Instance 3"; } } public string Version { get { return "1.1.0.0"; } } public string Description { get { return "Some Rule Instance"; } } } What if I want Name, Version and Description to come from a database? How would I tell MEF where to get that information? I may be missing something very obvious, but I don't know what it is. Thanks! Joel

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• Why is Core Data not persisting these changes to disk?

  - by scott

  I added a new entity to my model and it loads fine but no changes made in memory get persisted to disk. My values set on the car object work fine in memory but aren't getting persisted to disk on hitting the home button (in simulator). I am using almost exactly the same code on another entity in my application and its values persist to disk fine (core data - sqlite3); Does anyone have a clue what I'm overlooking here? Car is the managed object, cars in an NSMutableArray of car objects and Car is the entity and Visible is the attribute on the entity which I am trying to set. Thanks for you assistance. Scott - (void)viewDidLoad { myAppDelegate* appDelegate = (myAppDelegate*)[[UIApplication sharedApplication] delegate]; NSManagedObjectContext* managedObjectContex = appDelegate.managedObjectContext; NSFetchRequest* request = [[NSFetchRequest alloc] init]; NSEntityDescription* entity = [NSEntityDescription entityForName:@"Car" inManagedObjectContext:managedObjectContex]; [request setEntity:entity]; NSSortDescriptor* sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Name" ascending:YES]; NSArray* sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [sortDescriptor release]; NSError* error = nil; cars = [[managedObjectContex executeFetchRequest:request error:&error] mutableCopy]; if (cars == nil) { NSLog(@"Can't load the Cars data! Error: %@, %@", error, [error userInfo]); } [request release]; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath*)indexPath { Car* car = [cars objectAtIndex:indexPath.row]; if (car.Visible == [NSNumber numberWithBool:YES]) { car.Visible = [NSNumber numberWithBool:NO]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone; } else { car.Visible = [NSNumber numberWithBool:YES]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark; } }

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• Using collections/containers/catalogs in Domain Models

  - by devoured elysium

  Let's say I want to model a cinema. The cinema will have a couple of rooms(for example, 7), where the movies are being played. I wonder how should I design the domain model for this scenario. Should the Cinema class concept concept have a direct association with the 7 rooms? Should the Cinema class concept have an association with a catalog of the 7 rooms? Why? I am having some trouble understanding why in some places I see the first case and in some others I see something like the second case. If instead of rooms, I wanted to depict the relationship between Cinema and: Tickets to sell (today). Tickets already sold (today) Customers in the Cinema database The set of hours at which there are movies playing in a given room in the cinema. The set of places you can sit at in a room in the cinema. Should I use catalogs, should I connect them directly to the Cinema concept with a multiplicity of * in the target? Thanks

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• C# using the "this" keyword in this situation?

  - by Alex

  Hi, I've completed a OOP course assignment where I design and code a Complex Number class. For extra credit, I can do the following: Add two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When adding two complex numbers, the real part of the calling object is added to the real part of the complex number object passed as a parameter, and the imaginary part of the calling object is added to the imaginary part of the complex number object passed as a parameter. Subtract two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When subtracting two complex numbers, the real part of the complex number object passed as a parameter is subtracted from the real part of the calling object, and the imaginary part of the complex number object passed as a parameter is subtracted from the imaginary part of the calling object. I have coded this up, and I used the this keyword to denote the current instance of the class, the code for my add method is below, and my subtract method looks similar: public ComplexNumber Add(ComplexNumber c) { double realPartAdder = c.GetRealPart(); double complexPartAdder = c.GetComplexPart(); double realPartCaller = this.GetRealPart(); double complexPartCaller = this.GetComplexPart(); double finalRealPart = realPartCaller + realPartAdder; double finalComplexPart = complexPartCaller + complexPartAdder; ComplexNumber summedComplex = new ComplexNumber(finalRealPart, finalComplexPart); return summedComplex; } My question is: Did I do this correctly and with good style? (using the this keyword)?

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• Domain model for an optional many-many relationship

  - by Greg

  Let's say I'm modeling phone numbers. I have one entity for PhoneNumber, and one for Person. There's a link table that expresses the link (if any) between the PhoneNumber and Person. The link table also has a field for DisplayOrder. When accessing my domain model, I have several Use Cases for viewing a Person. I can look at them without any PhoneNumber information. I can look at them for a specific PhoneNumber. I can look at them and all of their current (or past) PhoneNumbers. I'm trying to model Person, not only for the standard CRUD operations, but for the (un)assignment of PhoneNumbers to a Person. I'm having trouble expressing the relationship between the two, especially with respects to the DisplayOrder property. I can think of several solutions but I'm not sure of which (if any) would be best. A PhoneNumberPerson class that has a Person and PhoneNumber property (most closely resembles database design) A PhoneCarryingPerson class that inherits from Person and has a PhoneNumber property. A PhoneNumber and/or PhoneNumbers property on Person (and vis-a-versa, a Person property on PhoneNumber) What would be a good way to model this that makes sense from a domain model perspective? How do I avoid misplaced properties (DisplayOrder on Person) or conditionally populated properties?

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• Most elegant way to break CSV columns into separate data structures using Python?

  - by Nick L

  I'm trying to pick up Python. As part of the learning process I'm porting a project I wrote in Java to Python. I'm at a section now where I have a list of CSV headers of the form: headers = [a, b, c, d, e, .....] and separate lists of groups that these headers should be broken up into, e.g.: headers_for_list_a = [b, c, e, ...] headers_for_list_b = [a, d, k, ...] . . . I want to take the CSV data and turn it into dict's based on these groups, e.g.: list_a = [ {b:val_1b, c:val_1c, e:val_1e, ... }, {b:val_2b, c:val_2c, e:val_2e, ... }, {b:val_3b, c:val_3c, e:val_3e, ... }, . . . ] where for example, val_1b is the first row of the 'b' column, val_3c is the third row of the 'c' column, etc. My first "Java instinct" is to do something like: for row in data: for col_num, val in enumerate(row): col_name = headers[col_num] if col_name in group_a: dict_a[col_name] = val elif headers[col_cum] in group_b: dict_b[col_name] = val ... list_a.append(dict_a) list_b.append(dict_b) ... However, this method seems inefficient/unwieldy and doesn't posses the elegance that Python programmers are constantly talking about. Is there a more "Zen-like" way I should try- keeping with the philosophy of Python?

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• How do I use Core Data with the Cocoa Text Input system?

  - by the Joel

  Hobbyist Cocoa programmer here. Have been looking around all the usual places, but this seems relatively under-explained: I am writing something a little out of the ordinary. It is much simpler than, but similar to, a desktop publishing app. I want editable text boxes on a canvas, arbitrarily placed. This is document-based and I’d really like to use Core Data. Now, The cocoa text-handling system seems to deal with a four-class structure: NSTextStorage, NSLayoutManager, NSTextContainer and finally NSTextView. I have looked into these and know how to use them, sort of. Have been making some prototypes and it works for simple apps. The problem arrives when I get into persistency. I don't know how to, by way of Cocoa Bindings or something else, store the contents of NSTextStorage (= the actual text) in my managed object context. I have considered overriding methods pairs like -words, -setWords: in these objects. This would let me link the words to a String, which I know how to store in Core Data. However, I’d have to override any method that affects the text - and that seems a little much. Thankful for any insights.

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• Update graph in real time from server

  - by user1869421

  I'm trying to update a graph with received data, so that the height of the bars increase as more data is received from the server via a websocket. But my code doesn't render a graph in the browser and plot the data points. I cannot see anything wrong with the code. I really need some help here please. ws = new WebSocket("ws://localhost:8888/dh"); var useData = [] //var chart; var chart = d3.select("body") .append("svg:svg") .attr("class", "chart") .attr("width", 420) .attr("height", 200); ws.onmessage = function(evt) { var distances = JSON.parse(evt.data); data = distances.miles; console.log(data); if(useData.length <= 10){ useData.push(data) } else { var draw = function(data){ // Set the width relative to max data value var x = d3.scale.linear() .domain([0, d3.max(useData)]) .range([0, 420]); var y = d3.scale.ordinal() .domain(useData) .rangeBands([0, 120]); var rect = chart.selectAll("rect") .data(useData) // enter rect rect.enter().append("svg:rect") .attr("y", y) .attr("width", x) .attr("height", y.rangeBand()); // update rect rect .attr("y", y) .attr("width", x) .attr("height", y.rangeBand()); var text = chart.selectAll("text") .data(useData) // enter text text.enter().append("svg:text") .attr("x", x) .attr("y", function (d) { return y(d) + y.rangeBand() / 2; }) .attr("dx", -3) // padding-right .attr("dy", ".35em") // vertical-align: middle .attr("text-anchor", "end") // text-align: right .text(String); // update text text .data(useData) .attr("x", x) .text(String); } useData.length = 0; } } Thanks

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• Avoid an "out of memory error" in Java(eclipse), when using large data structure?

  - by gnomed

  OK, so I am writing a program that unfortunately needs to use a huge data structure to complete its work, but it is failing with a "out of memory error" during its initialization. While I understand entirely what that means and why it is a problem, I am having trouble overcoming it, since my program needs to use this large structure and I don't know any other way to store it. The program first indexes a large corpus of text files that I provide. This works fine. Then it uses this index to initialize a large 2D array. This array will have nXn entries, where "n" is the number of unique words in the corpus of text. For the relatively small chunk I am testing it on(about 60 files) it needs to make approximately 30,000x30,000 entries. this will probably be bigger once I run it on my full intended corpus too. It consistently fails every time, after it indexes, while it is initializing the data structure(to be worked on later). Things I have done include: revamp my code to use a primitive "int[]" instead of a "TreeMap" eliminate redundant structures, etc... Also, I have run eclipse with "eclipse -vmargs -Xmx2g" to max out my allocated memory I am fairly confident this is not going to be a simple line of code solution, but is most likely going to require a very new approach. I am looking for what that approach is, any ideas? Thanks, B.

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• Improve this generic abstract class

  - by Keivan

  I have the following abstract class design, I was wondering if anyone can suggest any improvements in terms of stronger enforcement of our requirements or simplifying implementing of the ControllerBase. //Dependency Provider base public abstract class ControllerBase<TContract, TType> where TType : TContract, class { public static TContract Instance { get { return ComponentFactory.GetComponent<TContract, TType>(); } } public TContract GetComponent<TContract, TType>() where TType : TContract, class { component = (TType)Activator.CreateInstance(typeof(TType), true); RegisterComponentInstance<TContract>(component); } } //Contract public interface IController { void DoThing(); } //Actual Class Logic public class Controller: ControllerBase<IController,Controller> { public void DoThing(); //internal constructor internal Controller(){} } //Usage public static void Main() { Controller.Instance.DoThing(); } The following facts should always be true, TType should always implement TContract (Enforced using a generic constraint) TContract must be an interface (Can't find a way to enforce it) TType shouldn't have public constructor, just an internal one, is there any way to Enforce that using ControllerBase? TType must be an concrete class (Didn't include New() as a generic constrain since the constructors should be marked as Internal)

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• Where to start when doing a Domain Model?

  - by devoured elysium

  Let's say I've made a list of concepts I'll use to draw my Domain Model. Furthermore, I have a couple of Use Cases from which I did a couple of System Sequence Diagrams. When drawing the Domain Model, I never know where to start from: Designing the model as I believe the system to be. This is, if I am modelling a the human body, I start by adding the class concepts of Heart, Brain, Bowels, Stomach, Eyes, Head, etc. Start by designing what the Use Cases need to get done. This is, if I have a Use Case which is about making the human body swallow something, I'd first draw the class concepts for Mouth, Throat, Stomatch, Bowels, etc. The order in which I do things is irrelevant? I'd say probably it'd be best to try to design from the Use Case concepts, as they are generally what you want to work with, not other kind of concepts that although help describe the whole system well, much of the time might not even be needed for the current project. Is there any other approach that I am not taking in consideration here? How do you usually approach this? Thanks

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• When to define SDD operations System->Actor?

  - by devoured elysium

  I am having some trouble understanding how to make SDDs, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The user tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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• A data structure based on the R-Tree: creating new child nodes when a node is full, but what if I ha

  - by Tom

  I realize my title is not very clear, but I am having trouble thinking of a better one. If anyone wants to correct it, please do. I'm developing a data structure for my 2 dimensional game with an infinite universe. The data structure is based on a simple (!) node/leaf system, like the R-Tree. This is the basic concept: you set howmany childs you want a node (a container) to have maximum. If you want to add a leaf, but the node the leaf should be in is full, then it will create a new set of nodes within this node and move all current leafs to their new (more exact) node. This way, very populated areas will have a lot more subdivisions than a very big but rarely visited area. This works for normal objects. The only problem arises when I have more than maxChildsPerNode objects with the exact same X,Y location: because the node is full, it will create more exact subnodes, but the old leafs will all be put in the exact same node again because they have the exact same position -- resulting in an infinite loop of creating more nodes and more nodes. So, what should I do when I want to add more leafs than maxChildsPerNode with the exact same position to my tree? PS. if I failed to explain my problem, please tell me, so I can try to improve the explanation.

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• stdio data from write not making it into a file

  - by user1551209

  I'm having a problem with using stdio commands for manipulating data in a file. I short, when I write data into a file, write returns an int indicating that it was successful, but when I read it back out I only get the old data. Here's a stripped down version of the code: fd = open(filename,O_RDWR|O_APPEND); struct dE *cDE = malloc(sizeof(struct dE)); //Read present data printf("\nreading values at %d\n",off); printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET)); printf("ReadStatus <%d>\n",read(fd,cDE,deSize)); printf("current Key/Data <%d/%s>\n",cDE->key,cDE->data); printf("\nwriting new values\n"); //Change the values locally cDE->key = //something new cDE->data = //something new //Write them back printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET)); printf("WriteStatus <%d>\n",write(fd,cDE,deSize)); //Re-read to make sure that it got written back printf("\nre-reading values at %d\n",off); printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET)); printf("ReadStatus <%d>\n",read(fd,cDE,deSize)); printf("current Key/Data <%d/%s>\n",cDE->key,cDE->data); Furthermore, here's the dE struct in case you're wondering: struct dE { int key; char data[DataSize]; }; This prints: reading values at 1072 SeekStatus <1072> ReadStatus <32> current Key/Data <27/old> writing new values SeekStatus <1072> WriteStatus <32> re-reading values at 1072 SeekStatus <1072> ReadStatus <32> current Key/Data <27/old>

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• Should I put actors in the Domain-Model/Class-Diagram?

  - by devoured elysium

  When designing both the domain-model and class-diagrams I am having some trouble understanding what to put in them. I'll give an example of what I mean: I am doing a vacations scheduler program, that has an Administrator and End-Users. The Administrator does a couple of things like registering End-Users in the program, changing their previleges, etc. The End-User can choose his vacations days, etc. I initially defined an Administrator and End-User as concepts in the domain-model, and later as classes in the class-diagram. In the class-diagram, both classes ended up having a couple of methods like Administrator.RegisterNewUser(); Administrator.UnregisterUser(int id); etc. Only after some time I realised that actually both Administrator and End-User are actors, and maybe I got this design totally wrong. Instead of filling Administrator and End-User classes with methods to do what my Use-Cases request, I could define other classes from the domain to do them, and have controllers handle the Use-Cases(actually, I decided to do one for each Use-Case). I could have a UserDatabase.RegisterNewUser() and UserDatabase.UnregisterUser(int id);, for example, instead of having those methods on the Administrator class. The idea would be to try to think of the whole vacation-scheduler as a "closed-program" that has a set of features and doesn't bother with things such as authentication, that should be internal/protected, being that the only public things I'd let the outside world see would be its controllers. Is this the right approach? Or am I getting this totally wrong? Is it generally bad idea to put Actors in the domain-model/class-diagrams? What are good rules of thumb for this? My lecturer is following Applying UML and Patterns, which I find awful, so I'd like to know where I could look up more info on this described actor-models situation. I'm still a bit confused about all of this, as this new approach is radically different from anything I've done before.

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• When to define SDD(System Sequence Diagram) operations System->Actor?

  - by devoured elysium

  I am having some trouble understanding how to make System Sequence Diagrams, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: Let's assume the System is a Cinema Ticket Store and the Actor is a client that wants to buy a ticket. 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The User tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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