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  • Table design issues - should I create separate fields or store as a blob

    - by Ali
    Hi guys I'm working on my web based ordering system and we would like to maintain a kind of task history for each of our orders. A hsitory in the sense that we would like to maintain a log of who did what on an order like lets say an order has been entered - we would like to know if the order was acknowledged for an example. Or lets say somebody followed up on the order - etc. Consider that there are numerous situations like this for each order would it be wise to create a schema on the lines of: Orders ID - title - description - date - is_ack - is_follow - ack_by ..... That accounts to a lot of fields - on teh other hand I could have one LongText field called 'history' and fill it with a serialised object holding all the information. However in the latter case I can't run a query to lets say retrieve all orders that have not been acknowledged and stuff like that. With time requirements woudl change and I would be required to modify it to allow for more detailed tracking and that is why I need to set up a way which would be feasible to scale upon yet I don't want to be restricted on the SQL side too much.

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  • Signals and threads - good or bad design decision?

    - by Jens
    I have to write a program that performs highly computationally intensive calculations. The program might run for several days. The calculation can be separated easily in different threads without the need of shared data. I want a GUI or a web service that informs me of the current status. My current design uses BOOST::signals2 and BOOST::thread. It compiles and so far works as expected. If a thread finished one iteration and new data is available it calls a signal which is connected to a slot in the GUI class. My question(s): Is this combination of signals and threads a wise idea? I another forum somebody advised someone else not to "go down this road". Are there potential deadly pitfalls nearby that I failed to see? Is my expectation realistic that it will be "easy" to use my GUI class to provide a web interface or a QT, a VTK or a whatever window? Is there a more clever alternative (like other boost libs) that I overlooked? following code compiles with g++ -Wall -o main -lboost_thread-mt <filename>.cpp code follows: #include <boost/signals2.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <iostream> #include <iterator> #include <string> using std::cout; using std::cerr; using std::string; /** * Called when a CalcThread finished a new bunch of data. */ boost::signals2::signal<void(string)> signal_new_data; /** * The whole data will be stored here. */ class DataCollector { typedef boost::mutex::scoped_lock scoped_lock; boost::mutex mutex; public: /** * Called by CalcThreads call the to store their data. */ void push(const string &s, const string &caller_name) { scoped_lock lock(mutex); _data.push_back(s); signal_new_data(caller_name); } /** * Output everything collected so far to std::out. */ void out() { typedef std::vector<string>::const_iterator iter; for (iter i = _data.begin(); i != _data.end(); ++i) cout << " " << *i << "\n"; } private: std::vector<string> _data; }; /** * Several of those can calculate stuff. * No data sharing needed. */ struct CalcThread { CalcThread(string name, DataCollector &datcol) : _name(name), _datcol(datcol) { } /** * Expensive algorithms will be implemented here. * @param num_results how many data sets are to be calculated by this thread. */ void operator()(int num_results) { for (int i = 1; i <= num_results; ++i) { std::stringstream s; s << "["; if (i == num_results) s << "LAST "; s << "DATA " << i << " from thread " << _name << "]"; _datcol.push(s.str(), _name); } } private: string _name; DataCollector &_datcol; }; /** * Maybe some VTK or QT or both will be used someday. */ class GuiClass { public: GuiClass(DataCollector &datcol) : _datcol(datcol) { } /** * If the GUI wants to present or at least count the data collected so far. * @param caller_name is the name of the thread whose data is new. */ void slot_data_changed(string caller_name) const { cout << "GuiClass knows: new data from " << caller_name << std::endl; } private: DataCollector & _datcol; }; int main() { DataCollector datcol; GuiClass mc(datcol); signal_new_data.connect(boost::bind(&GuiClass::slot_data_changed, &mc, _1)); CalcThread r1("A", datcol), r2("B", datcol), r3("C", datcol), r4("D", datcol), r5("E", datcol); boost::thread t1(r1, 3); boost::thread t2(r2, 1); boost::thread t3(r3, 2); boost::thread t4(r4, 2); boost::thread t5(r5, 3); t1.join(); t2.join(); t3.join(); t4.join(); t5.join(); datcol.out(); cout << "\nDone" << std::endl; return 0; }

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  • Flexible design - customizable entity model, UI and workflow

    - by Ngm
    Hi All, I want to achieve the following aspects in the software I am building: 1. Customizable entity model 2. Customizable UI 3. Customizable workflow I have thought about an approach to achieve this, I want you to review this and make suggestions: Entity objects should be plain objects and will hold just data Separate Entity model and DB Schema by using an framework (like NHibernate?). This will allow easy modification of entity objects. Business logic to fetch/modify entities has to be granular enough so that they can be invoked as part of the workflow. Business objects should not hold any state, and hence will contain only static methods The workflow will decide depending upon the "state" of an entity/entities which methods on business object/objects to invoke. The workflow should obtain the results of the processing and then pass on the business objects to the appropriate UI screen. The UI screen has to contain instructions about how to display a given entity/entites. Possibly the UI has to be generated dynamically based on a set of UI instructions. (like XUL) What do you think about this approach? Suggest which existing frameworks (like NHiberante, Window Workflow) fit into this model, so that I will not spend time on coding these frameworks Also suggest is there any asp.net framework that can generate dynamic asp.net ajax pages based on a set of UI instructions (like Mozilla XUL)? I have recently been exploring Apache Ofbiz and was impressed by its ability to customize most areas of the application: UI, workflow, entities. Is there any similar (not necessarily an ERP system) application developed in C#/.Net which offers a similar level of customization? I am looking for examples of applications developed in C# that are highly customizable in terms of UI, Workflow and Entity Model

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  • OOP, Interface Design and Encapsulation

    - by Mau
    C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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  • Android listing design problem with cursors

    - by Priyank
    Hi. I have a following situation in my android app. I have an app that fetches messages from inbox, sent items and drafts based on search keywords. I use to accomplish this by fetching cursors for each manually based on selection by user and then populating them in a custom data holder object. Filter those results based on given keywords and then manually render view with respective data. Someone suggested that I should use a custom Cursor adapter to bind view and my cursor data. So I tried doing that. Now what I am doing is this: Fetch individual cursors for inbox, sent items and drafts. Merge them into one using Merge cursor and then pass that back to my CursorAdapter implmentation. Now where or how do I filter my cursor data based on keywords; because now binding will ensure that they are directly rendered to view on list. Also, some post fetching operation like fetching sender's contact pic and all will be something that I do not want to move to adapter. If I do all this processing in adapter; it'll be heavy and ugly. How could I have designed it better such that it performs and the responsibilities are shared and distributed. Any ideas will be helpful.

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  • Comparing two Objects which implement the same interface for equality / equivalence - Design help

    - by gav
    Hi All, I have an interface and two objects implementing that interface, massively simplied; public interface MyInterface { public int getId(); public int getName(); ... } public class A implements MyInterface { ... } public class B implements MyInterface { ... } We are migrating from using one implementation to the other but I need to check that the objects of type B that are generated are equivalent to those of type A. Specifically I mean that for all of the interface methods an object of Type A and Type B will return the same value (I'm just checking my code for generating this objects is correct). How would you go about this? Map<String, MyInterface> oldGeneratedObjects = getOldGeneratedObjects(); Map<String, MyInterface> newGeneratedObjects = getNewGeneratedObjects(); // TODO: Establish that for each Key the Values in the two maps return equivalent values. I'm looking for good coding practices and style here. I appreciate that I could just iterate through one key set pulling out both objects which should be equivalent and then just call all the methods and compare, I'm just thinking there may be a cleaner, more extensible way and I'm interested to learn what options there might be. Would it be appropriate / possible / advised to override equals or implement Comparable? Thanks in advance, Gavin

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  • Design pattern to integrate Rails with a Comet server

    - by empire29
    I have a Ruby on Rails (2.3.5) application and an APE (Ajax Push Engine) server. When records are created within the Rails application, i need to push the new record out on applicable channels to the APE server. Records can be created in the rails app by the traditional path through the controller's create action, or it can be created by several event machines that are constantly monitoring various inputstream and creating records when they see data that meets a certain criteria. It seems to me that the best/right place to put the code that pushes the data out to the APE server (which in turn pushes it out to the clients) is in the Model's after_create hook (since not all record creations will flow through the controller's create action). The final caveat is I want to push a piece of formatted HTML out to the APE server (rather than a JSON representation of the data). The reason I want to do this is 1) I already have logic to produce the desired layout in existing partials 2) I don't want to create a javascript implementation of the partials (javascript that takes a JSON object and creates all the HTML around it for presentation). This would quickly become a maintenance nightmare. The problem with this is it would require "rendering" partials from within the Model (which im having trouble doing anyhow because they don't seem to have access to Helpers when they're rendered in this manner). Anyhow - Just wondering what the right way to go about organizing all of this is. Thanks

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  • Python OOP - object has no attribute

    - by user1744269
    I am attempting to learn how to program. I really do want to learn how to program; I love the building and design aspect of it. However, in Java and Python, I have tried and failed with programs as they pertain to objects, classes, methods.. I am trying to develop some code for a program, but im stumped. I know this is a simple error. However I am lost! I am hoping someone can guide me to a working program, but also help me learn (criticism is not only expected, but APPRECIATED). class Converter: def cTOf(self, numFrom): numFrom = self.numFrom numTo = (self.numFrom * (9/5)) + 32 print (str(numTo) + ' degrees Farenheit') return numTo def fTOc(self, numFrom): numFrom = self.numFrom numTo = ((numFrom - 32) * (5/9)) return numTo convert = Converter() numFrom = (float(input('Enter a number to convert.. '))) unitFrom = input('What unit would you like to convert from.. ') unitTo = input('What unit would you like to convert to.. ') if unitFrom == ('celcius'): convert.cTOf(numFrom) print(numTo) input('Please hit enter..') if unitFrom == ('farenheit'): convert.fTOc(numFrom) print(numTo) input('Please hit enter..')

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  • Does this inheritance design belong in the database?

    - by Berryl
    === CLARIFICATION ==== The 'answers' older than March are not answers to the question in this post! Hello In my domain I need to track allocations of time spent on Activities by resources. There are two general types of Activities of interest - ones base on a Project and ones based on an Account. The notion of Project and Account have other features totally unrelated to both each other and capturing allocations of time, and each is modeled as a table in the database. For a given Allocation of time however, it makes sense to not care whether the allocation was made to either a Project or an Account, so an ActivityBase class abstracts away the difference. An ActivityBase is either a ProjectActivity or an AccountingActivity (object model is below). Back to the database though, there is no direct value in having tables for ProjectActivity and AccountingActivity. BUT the Allocation table needs to store something in the column for it's ActivityBase. Should that something be the Id of the Project / Account or a reference to tables for ProjectActivity / Accounting? How would the mapping look? === Current Db Mapping (Fluent) ==== Below is how the mapping currently looks: public class ActivityBaseMap : IAutoMappingOverride<ActivityBase> { public void Override(AutoMapping<ActivityBase> mapping) { //mapping.IgnoreProperty(x => x.BusinessId); //mapping.IgnoreProperty(x => x.Description); //mapping.IgnoreProperty(x => x.TotalTime); mapping.IgnoreProperty(x => x.UniqueId); } } public class AccountingActivityMap : SubclassMap<AccountingActivity> { public void Override(AutoMapping<AccountingActivity> mapping) { mapping.References(x => x.Account); } } public class ProjectActivityMap : SubclassMap<ProjectActivity> { public void Override(AutoMapping<ProjectActivity> mapping) { mapping.References(x => x.Project); } } There are two odd smells here. Firstly, the inheritance chain adds nothing in the way of properties - it simply adapts Projects and Accounts into a common interface so that either can be used in an Allocation. Secondly, the properties in the ActivityBase interface are redundant to keep in the db, since that information is available in Projects and Accounts. Cheers, Berryl ==== Domain ===== public class Allocation : Entity { ... public virtual ActivityBase Activity { get; private set; } ... } public abstract class ActivityBase : Entity { public virtual string BusinessId { get; protected set; } public virtual string Description { get; protected set; } public virtual ICollection<Allocation> Allocations { get { return _allocations.Values; } } public virtual TimeQuantity TotalTime { get { return TimeQuantity.Hours(Allocations.Sum(x => x.TimeSpent.Amount)); } } } public class ProjectActivity : ActivityBase { public virtual Project Project { get; private set; } public ProjectActivity(Project project) { BusinessId = project.Code.ToString(); Description = project.Description; Project = project; } }

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  • How to convert an object into a double?

    - by george t.
    I am working on VS C# on the following code, which converts an user input math expression and computes it. MSScriptControl.ScriptControl sc = new MSScriptControl.ScriptControl(); sc.Language = "VBScript"; sc.ExecuteStatement( "function pi\n" + "pi = 3.14159265\n" + "end function"); sc.ExecuteStatement( "function e\n" + "e = exp(1)\n" + "end function"); expression = textBox1.Text.ToString(); expression = expression.Replace("x", i.ToString()); object y = sc.Eval(expression); string k = y.ToString(); double result = double.Parse(k); While this outputs onto the console with the correct result, I want to use the values to make a graph of the function user inputs and it's not doing it correctly. Thank you for your help.

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  • How to read a Choice Field from Sharepoint 2010 Client Object Model

    - by Eric
    Hello, I'm using Sharepoint 2010 Object Model. I'm trying to retrive the content of a Custom List. Everything works fine except if when I try to retrieve a Choice Field. When I try to retrieve the choice field, I got an PropertyOrFieldNotInitializedException exception... Here is the code I'm using: ClientContext clientContext = new ClientContext("https://mysite"); clientContext.FormsAuthenticationLoginInfo = new FormsAuthenticationLoginInfo("aaa", bbb"); clientContext.AuthenticationMode = ClientAuthenticationMode.FormsAuthentication; List list = clientContext.Web.Lists.GetByTitle("mylist"); CamlQuery camlQuery = new CamlQuery(); camlQuery.ViewXml = "<View/>"; ListItemCollection listItems = list.GetItems(camlQuery); clientContext.Load(listItems); clientContext.ExecuteQuery(); foreach (ListItem listItem in listItems) { listBoxControl1.Items.Add(listItem["Assigned_x0020_Company"]); } Thank you for you help! Eric

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  • Unable to cast object of type 'System.Object[]' to type 'System.String[]'

    - by salvationishere
    I am developing a C# VS 2008 / SQL Server website application. I am a newbie to ASP.NET. I am getting the above error, however, on the last line of the following code. Can you give me advice on how to fix this? This compiles correctly, but I encounter this error after running it. DataTable dt; Hashtable ht; string[] SingleRow; ... SqlConnection conn2 = new SqlConnection(connString); SqlCommand cmd = conn2.CreateCommand(); cmd.CommandText = "dbo.AppendDataCT"; cmd.Connection = conn2; SingleRow = (string[])dt.Rows[1].ItemArray; My error: System.InvalidCastException was caught Message="Unable to cast object of type 'System.Object[]' to type 'System.String[]'." Source="App_Code.g68pyuml" StackTrace: at ADONET_namespace.ADONET_methods.AppendDataCT(DataTable dt, Hashtable ht) in c:\Documents and Settings\Admin\My Documents\Visual Studio 2008\WebSites\Jerry\App_Code\ADONET methods.cs:line 88 InnerException:

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  • EMBED vs. OBJECT

    - by JayhawksFan93
    Which is the right/best tag to use in my HTML file when I want to display the Adobe PDF viewer? Right now I'm using the code below, but there are weird side effects (e.g. it seems to steal the starting focus that I've set to another INPUT text box; it doesn't seem to play real well with the jQueryUI Resizeable class; etc.) <embed src="abc.pdf" type="application/pdf" /> Could I even do the same thing with the OBJECT tag? Are there advantages/disadvantages to using one tag vs. the other?

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  • Runtime Error 424 Object Required

    - by Luis
    Hey so I get this error in this code: Private Sub Request_Stuff_button_Click() Call Main.createObjects Call My_Control.requestStuff End Sub at the 'Call My_Control.requestStuff' line. The 'Main' module looks like this: Public My_Control As ControlObject Public Sub createObjects() If My_Control Is Nothing Then Set My_Control = New ControlObject End If End Sub The weirdest thing is that when I add Dim x As Integer x = My_Control.dummyInt right before the line that gets me the error, x gets the correct value right before the error happens which means My_Control is definitely an object and is definitely not nothing. This error is killing me, thanks in advance.

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  • How to map IEnumerable<SelectListItem> to IList<> for ListBox

    - by Superhuman
    I have two classes. Class1 and Class2. public class Class1{ ... public virtual IList<Class2> Class2s{get;set;} ... } public class Class2{ ... public virtual IList<Class1> Class1s{get;set;} ... } The view contains <%=Html.ListBox("Class2s", ViewData.Model.Class2s.Select( x => new SelectListItem { Text = x.Name, Value = x.Id.ToString(), Selected = ViewData.Model.Class1.Class2s.Any(y => y.Id == x.Id) }) They have many to many mapping. I have a ListBox in Class1 view which displays Class2. How to map the output of the ListBox back to IList Class2s property of Class1? I am able to display the values in the ListBox but unable to map back the SelectListItem to IList.

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  • Is there a way to put relationships/contraints into CSS?

    - by hekevintran
    In every design tool or art principle I've heard of, relationships are a central theme. By relationships I mean the thing you can do in Adobe Illustrator to specify that the height of one shape is equal to half the height of another. You cannot express this information in CSS. CSS hard-codes all values. Using a language like LESS that allows variables and arithmetic you can get closer to relationships but it's still a CSS variant. This inability in my mind is the biggest problem with CSS. CSS is supposed to be a language that describes the visual component of a Web page but it ignores relationships and contraints, ideas that are at the core of art. How possible is it to imagine a new Web design language that can express relationships and contraints that can be implemented in JavaScript using the current CSS properties?

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  • What is the difference between JSON and Object Literal Notation?

    - by burak ozdogan
    Hi, Can someone tell me what is the main difference between a Javascript object defined by using "Object Literal Notation" and JSON object? According to a Javascript book it says this is an object defined by using Object Notation: var newObject = { prop1 : true, showMessage : function (msg) {alert(msg)} }; Why it is not a JSON object in this case? Just because it is not defined by using quotation marks? Thanks,

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  • Object tree navigation language in Java

    - by lewap
    In the system which I'm currently developing I often have to navigate an object tree and based on its state and values take actions. In normal Java this results in tedious for loops, if statements etc... Are there alternative ways to achieve tree navigation, similar to XPath for XML? I know there is JXPath and OGNL, but do you know any other libraries for such purpose? Do you know any libraries which generate bytecodes for specific tree navigation expressions to make the processing as fast as Java native fors and ifs?

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  • (MyClassName)object vs. object as MyClassName

    - by Matthew Doyle
    Hello all, I was wondering what is the better method for Casting objects for C#: MyClassName test = (MyClassName)object; MyClassName test = object as MyClassName; I know already that if you do the first way, you get an exception, and the second way it sets test as null. However, I was wondering why do one over the other? I see the first way a lot, but I like how the second way because then I can check for null... If there isn't a 'better way' of doing it, what are the guidelines for using one way or the other?

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  • How are java.lang.Object's protected methods protected from subclasses?

    - by Adrian Lang
    The keyword protected grants access to classes in the same package and subclasses (http://java.sun.com/docs/books/tutorial/java/javaOO/accesscontrol.html). Now, every class has java.lang.Object as superclass (http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.html). Hence I conclude that every class may access java.lang.Object's methods even if they are protected. Take a look at the following example: public class Testclass { public Object getOne() throws CloneNotSupportedException { return this.clone(); } public Object getTwo() throws CloneNotSupportedException { return ((Object) this).clone(); } } While getOne() compiles fine, getTwo() gives Testclass.java:6: clone() has protected access in java.lang.Object return ((Object) this).clone(); I neither understand why getTwo() doesn't compile nor what's the difference (regarding the access of java.lang.Objects members) with getOne().

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  • Hibernate -using Table per subclass - how to link an existing superclass object to a sibclass object

    - by Chandni
    Hi, I have a User hibernate class, Clerk class and Consumer class. All these maps to their own tables in database. The User PK also acts as Clerk's and Consumer's PK. So now my problem is that if a user is initially a Clerk, he has a record in Users table and Clerks table. If that user wants to become a consumer, I want to link that User's record to the new Consumer's record. So even if I pass the userId to the consumer's record, it treats it as a new User to be persisted and gives a duplicate_key exception. How do I tell Hiernate to link the same user object with this new Consumer object. Thanks in advance, -Chandni

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  • In this context with views in a tree, which class should perform the task?

    - by Jhonny 8
    Imagine that I have this context: A main view containing a table containing some cells. Each one of them with their own controller and view files. In the main view, I have an object "Person", with 3 different IDs. Depending on certain conditions (let say, time of the day), I have to choose one of them and display it in the cell. My question is, should the main view pass the whole object to the table, and this one to the cell, and the cell will calculate the ID that it will be shown? or, The main view calculates this parameter, and send the result to the table and this to the cell? Is a question focused on OO design, which one of this approaches is more suitable in an OO design and why?

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  • Converting HTML TAG Object to JSON Object

    - by cooldude
    Hi, I want to convert the html tag objects to json object in the javascript in order to send them to the server from the javascript. As i have to save these objects at the Ruby on Rails server. These HTML objects is the canvas tag object and the graphics objects created using CAKE API. I have used the stringify function but it is not working. Here is my code: var CAKECanvas = new Canvas(document.body, 1000,1000); var canvas=CAKECanvas.canvas; var text=document.createElement('textarea'); text.id="text"; text.rows="100"; text.cols="200"; document.body.appendChild(text); canvas.style.borderStyle="solid"; canvas.style.borderColor="black"; var rect= new Circle(); rect.radius=100; rect.centered=true; rect.cx=Math.random() * 500; rect.cy= Math.random() * 300; rect.stroke= false; rect.fill= "red"; rect.xDir = Math.random() > 0.5?1:-1; rect.yDir = Math.random() > 0.5?1:-1; var obj=new Object; var count = 0,k; for (k in rect) { if (rect.hasOwnProperty(k)) { count++; obj[k]=rect[k]; } } alert(count); rect.addFrameListener(function(t, dt) { this.cx += this.xDir * 50 * dt/1000; this.cy += this.yDir * 50 * dt/1000; if (this.cx > 550) { this.xDir = -1; } if (this.cx < 50) { this.xDir = 1; } if (this.cy > 350) { this.yDir = -1; } if (this.cy < 50) { this.yDir = 1; } } ); CAKECanvas.append(rect); var carAsJSON = JSON.stringify(obj); /////////////////ERROR

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