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  • How to manage my model

    - by Christophe Debove
    I have in my model, a list of Classes : Player, NonPlayerCharacter, Monster, Item, NonMovableItem etc With AndEngine I've a list of sprite for each piece of my model, How can I manage the relashionship between my model's classes and the graphical elements, what is the degree of abstaction recommended for my problem? One sprite for one Model or one Model for one Sprite or n for n for exemple If I do drag&drop have I to make abstraction of the Sprite Class, another exemple a map is a List of sprite or a list of element of my model?

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  • How to play the sound of an object sliding on another object for a variable duration

    - by Antoine
    I would like to add sound effects to a basic 2D game. For example, a stone sphere is rolling on wood surface. Let's say I have a 2 second audio recording of this. How could I use the sample to add sound for an arbitrary duration ? So far I have two solutions in mind: a/ record the sound for an amount of time that is greater than the maximum expected duration, and play only a part of it; b/ extract a small portion of the sample and play it in a loop for the duration of the move; however I'm not sure if it makes sense with an audio wave.

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  • Using asp.net mvc model binders generically

    - by Sean Chambers
    I have a hierarchy of classes that all derive from a base type and the base type also implements an interface. What I'm wanting to do is have one controller to handle the management of the entire hierarchy (as the actions exposed via the controller is identical). That being said, I want to have the views have the type specific fields on it and the model binder to bind against a hidden field value. something like: <input type="text" name="model.DerivedTypeSpecificField" /> <input type="hidden" name="modelType" value="MyDerivedType" /> That being said, the asp.net mvc model binders seem to require the concrete type that they will be creating, because of that reason I would need to create a different controller for every derived type. Has anyone does this before or know how to manipulate the model binder to behave in this way? I could write my own model binder, but I'm not wanting anything past the basic model binding behavior of assign properties and building arrays on the target type. Thanks!

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  • Best practice for near reuse of model components?

    - by Chris Knight
    I have a requirement to use a Fund model in my code. It will contain a fund name and fund code. In the interest of reuse I've poked around the package containing the other models used and found an existing Fund model. However the issue here is that, in addition to fund name and code, it also contains an amount. Amount isn't directly relevant in my context. So, do I: 1) Use the existing Fund model as is, ignoring the setters/getters for fund amount. 2) Put a FundDescription interface onto the existing Fund model for accessing only the information I'm interested in. 3) Make a FundDescription base class from which the existing Fund model could now extend 4) Create a whole new seperate model since the two are slightly contextually different

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  • How to create a nested form in backbone relational?

    - by jebek
    I would like to be able to create nested models at the same time in backbone. I know how to use backbone relational to create the parent model. Then once it is saved, I can create child models through backbone relational. However, I want to be able to create both the parent and child models at the same time, which might not be possible because I can only create the child model once the parent model has already been created. For example, let's say I was creating a forum like the one from the awesome backbone relational tutorial - http://antoviaque.org/docs/tutorials/backbone-relational-tutorial/. I would want to create a thread and a message at the same time(through the click of a single button) rather than create a thread then a message. Is this possible? Is there a better way of doing this that I'm not thinking of?

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  • MVC DropDownListFor not populating the selected value

    - by user2254436
    I'm really having troubles with MVC, in another project I've done the same thing and it worked fine but in this project I just don't understand why the selected item in the dropdown is not populating the class correctly with EF. I have 2 classes: public partial class License { public License() { this.Customers = new HashSet<Customer>(); } public int LicenseID { get; set; } public int Lic_LicenseTypeID { get; set; } public int Lic_LicenseStatusID { get; set; } public string Lic_LicenseComments { get; set; } public virtual EntitiesList LicenseStatus { get; set; } public virtual EntitiesList LicenseType { get; set; } } public partial class EntitiesList { public EntitiesList() { this.LicensesStatus = new HashSet<License>(); this.LicensesType = new HashSet<License>(); } public int ListID { get; set; } public string List_EntityValue { get; set; } public string List_Comments { get; set; } public string List_EntityName { get; set; } public virtual ICollection<License> LicensesStatus { get; set; } public virtual ICollection<License> LicensesType { get; set; } public string List_DisplayName { get { return Regex.Replace(List_EntityName, "([a-z])([A-Z])", "$1 $2"); ; } } public string List_DisplayValue { get { return Regex.Replace(List_EntityValue, "([a-z])([A-Z])", "$1 $2"); } } } The EntitiesList is table in db that have all my "enum" lists. For example: ListID - 0 List_EntityValue - Activate List_EntityName - LicenseStatus ListID - 1 List_EntityValue - Basic List_EntityName - LicenseType This is my model: public class LicenseModel { public License License { get; set; } public SelectList LicenseStatuses { get; set; } public int SelectedStatus { get; set; } public SelectList LicenseTypes { get; set; } public int SelectedType { get; set; } } My controller for create: public ActionResult Create() { LicenseModel model = new LicenseModel(); model.License = new License(); model.LicenseStatuses = new SelectList(managerLists.GetAllLicenseStatuses(), "ListID", "List_DisplayValue"); model.LicenseTypes = new SelectList(managerLists.GetAllLicenseTypes(), "ListID", "List_DisplayValue"); return View(model); } [HttpPost] [ValidateAntiForgeryToken] public ActionResult Create(LicenseModel model) { if (ModelState.IsValid) { model.License.Lic_LicenseTypeID = model.SelectedType; model.License.Lic_LicenseStatusID = model.SelectedStatus; managerLicense.AddNewObject(model.License); return RedirectToAction("Index"); } return View(model); } managerLists and managerLicense are the managers that connect between the entities in db and the MVC UI, nothing special... they contains queries for adding new objects, getting the lists, editing and so on. And the view for creating the License: @using (Html.BeginForm()) { @Html.AntiForgeryToken() @Html.ValidationSummary(true) <fieldset> <legend>License</legend> <div class="form-group"> @Html.LabelFor(model => model.License.Lic_LicenseTypeID) @Html.DropDownListFor(model => model.SelectedType, Model.LicenseTypes, new { @class = "form-control" }) <p class="help-block">@Html.ValidationMessageFor(model => model.License.Lic_LicenseTypeID)</p> </div> <div class="form-group"> @Html.LabelFor(model => model.License.Lic_LicenseStatusID) @Html.DropDownListFor(model => model.SelectedStatus, Model.LicenseStatuses, new { @class = "form-control" }) <p class="help-block">@Html.ValidationMessageFor(model => model.License.Lic_LicenseStatusID)</p> </div> <div class="form-group"> @Html.LabelFor(model => model.License.Lic_LicenseComments) @Html.TextAreaFor(model => model.License.Lic_LicenseComments, new { @class = "form-control", rows = "3" }) <p class="help-block">@Html.ValidationMessageFor(model => model.License.Lic_LicenseComments)</p> </div> <p> <input type="submit" value="Create" /> </p> </fieldset> } Now, when I'm trying to save the new license, when it gets to the db.SaveChanges() in the manager I'm getting: "Validation failed for one or more entities. See 'EntityValidationErrors' property for more details." In breakpoint, the Lic_LicenseTypeID and Lic_LicenseStatusID are getting correctly the ID's from the selected item in the dropdown but the LicenseStatus and LicenseStatus properties are null. What an I missing?

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  • SQL SERVER – Enumerations in Relational Database – Best Practice

    - by pinaldave
    Marko Parkkola This article has been submitted by Marko Parkkola, Data systems designer at Saarionen Oy, Finland. Marko is excellent developer and always thinking at next level. You can read his earlier comment which created very interesting discussion here: SQL SERVER- IF EXISTS(Select null from table) vs IF EXISTS(Select 1 from table). I must express my special thanks to Marko for sending this best practice for Enumerations in Relational Database. He has really wrote excellent piece here and welcome comments here. Enumerations in Relational Database This is a subject which is very basic thing in relational databases but often not very well understood and sometimes badly implemented. There are of course many ways to do this but I concentrate only two cases, one which is “the right way” and one which is definitely wrong way. The concept Let’s say we have table Person in our database. Person has properties/fields like Firstname, Lastname, Birthday and so on. Then there’s a field that tells person’s marital status and let’s name it the same way; MaritalStatus. Now MaritalStatus is an enumeration. In C# I would definitely make it an enumeration with values likes Single, InRelationship, Married, Divorced. Now here comes the problem, SQL doesn’t have enumerations. The wrong way This is, in my opinion, absolutely the wrong way to do this. It has one upside though; you’ll see the enumeration’s description instantly when you do simple SELECT query and you don’t have to deal with mysterious values. There’s plenty of downsides too and one would be database fragmentation. Consider this (I’ve left all indexes and constraints out of the query on purpose). CREATE TABLE [dbo].[Person] ( [Firstname] NVARCHAR(100), [Lastname] NVARCHAR(100), [Birthday] datetime, [MaritalStatus] NVARCHAR(10) ) You have nvarchar(20) field in the table that tells the marital status. Obvious problem with this is that what if you create a new value which doesn’t fit into 20 characters? You’ll have to come and alter the table. There are other problems also but I’ll leave those for the reader to think about. The correct way Here’s how I’ve done this in many projects. This model still has one problem but it can be alleviated in the application layer or with CHECK constraints if you like. First I will create a namespace table which tells the name of the enumeration. I will add one row to it too. I’ll write all the indexes and constraints here too. CREATE TABLE [CodeNamespace] ( [Id] INT IDENTITY(1, 1), [Name] NVARCHAR(100) NOT NULL, CONSTRAINT [PK_CodeNamespace] PRIMARY KEY ([Id]), CONSTRAINT [IXQ_CodeNamespace_Name] UNIQUE NONCLUSTERED ([Name]) ) GO INSERT INTO [CodeNamespace] SELECT 'MaritalStatus' GO Then I create a table that holds the actual values and which reference to namespace table in order to group the values under different namespaces. I’ll add couple of rows here too. CREATE TABLE [CodeValue] ( [CodeNamespaceId] INT NOT NULL, [Value] INT NOT NULL, [Description] NVARCHAR(100) NOT NULL, [OrderBy] INT, CONSTRAINT [PK_CodeValue] PRIMARY KEY CLUSTERED ([CodeNamespaceId], [Value]), CONSTRAINT [FK_CodeValue_CodeNamespace] FOREIGN KEY ([CodeNamespaceId]) REFERENCES [CodeNamespace] ([Id]) ) GO -- 1 is the 'MaritalStatus' namespace INSERT INTO [CodeValue] SELECT 1, 1, 'Single', 1 INSERT INTO [CodeValue] SELECT 1, 2, 'In relationship', 2 INSERT INTO [CodeValue] SELECT 1, 3, 'Married', 3 INSERT INTO [CodeValue] SELECT 1, 4, 'Divorced', 4 GO Now there’s four columns in CodeValue table. CodeNamespaceId tells under which namespace values belongs to. Value tells the enumeration value which is used in Person table (I’ll show how this is done below). Description tells what the value means. You can use this, for example, column in UI’s combo box. OrderBy tells if the values needs to be ordered in some way when displayed in the UI. And here’s the Person table again now with correct columns. I’ll add one row here to show how enumerations are to be used. CREATE TABLE [dbo].[Person] ( [Firstname] NVARCHAR(100), [Lastname] NVARCHAR(100), [Birthday] datetime, [MaritalStatus] INT ) GO INSERT INTO [Person] SELECT 'Marko', 'Parkkola', '1977-03-04', 3 GO Now I said earlier that there is one problem with this. MaritalStatus column doesn’t have any database enforced relationship to the CodeValue table so you can enter any value you like into this field. I’ve solved this problem in the application layer by selecting all the values from the CodeValue table and put them into a combobox / dropdownlist (with Value field as value and Description as text) so the end user can’t enter any illegal values; and of course I’ll check the entered value in data access layer also. I said in the “The wrong way” section that there is one benefit to it. In fact, you can have the same benefit here by using a simple view, which I schema bound so you can even index it if you like. CREATE VIEW [dbo].[Person_v] WITH SCHEMABINDING AS SELECT p.[Firstname], p.[Lastname], p.[BirthDay], c.[Description] MaritalStatus FROM [dbo].[Person] p JOIN [dbo].[CodeValue] c ON p.[MaritalStatus] = c.[Value] JOIN [dbo].[CodeNamespace] n ON n.[Id] = c.[CodeNamespaceId] AND n.[Name] = 'MaritalStatus' GO -- Select from View SELECT * FROM [dbo].[Person_v] GO This is excellent write up byMarko Parkkola. Do you have this kind of design setup at your organization? Let us know your opinion. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Database, DBA, Readers Contribution, Software Development, SQL, SQL Authority, SQL Documentation, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Significant amount of the time, I can't think of a reason to have an object instead of a static class. Do objects have more benefits than I think?

    - by Prog
    I understand the concept of an object, and as a Java programmer I feel the OO paradigm comes rather naturally to me in practice. However recently I found myself thinking: Wait a second, what are actually the practical benefits of using an object over using a static class (with proper encapsulation and OO practices)? I could think of two benefits of using an object (both significant and powerful): Polymorphism: allows you to swap functionality dynamically and flexibly during runtime. Also allows to add new functionality 'parts' and alternatives to the system easily. For example if there's a Car class designed to work with Engine objects, and you want to add a new Engine to the system that the Car can use, you can create a new Engine subclass and simply pass an object of this class into the Car object, without having to change anything about Car. And you can decide to do so during runtime. Being able to 'pass functionality around': you can pass an object around the system dynamically. But are there any more advantages to objects over static classes? Often when I add new 'parts' to a system, I do so by creating a new class and instantiating objects from it. But recently when I stopped and thought about it, I realized that a static class would do just the same as an object, in a lot of the places where I normally use an object. For example, I'm working on adding a save/load-file mechanism to my app. With an object, the calling line of code will look like this: Thing thing = fileLoader.load(file); With a static class, it would look like this: Thing thing = FileLoader.load(file); What's the difference? Fairly often I just can't think of a reason to instantiate an object when a plain-old static-class would act just the same. But in OO systems, static classes are fairly rare. So I must be missing something. Are there any more advantages to objects other from the two that I listed? Please explain.

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  • OOP concept: is it possible to update the class of an instantiated object?

    - by Federico
    I am trying to write a simple program that should allow a user to save and display sets of heterogeneous, but somehow related data. For clarity sake, I will use a representative example of vehicles. The program flow is like this: The program creates a Garage object, which is basically a class that can contain a list of vehicles objects Then the users creates Vehicles objects, these Vehicles each have a property, lets say License Plate Nr. Once created, the Vehicle object get added to a list within the Garage object --Later on--, the user can specify that a given Vehicle object is in fact a Car object or a Truck object (thus giving access to some specific attributes such as Number of seats for the Car, or Cargo weight for the truck) At first sight, this might look like an OOP textbook question involving a base class and inheritance, but the problem is more subtle because at the object creation time (and until the user decides to give more info), the computer doesn't know the exact Vehicle type. Hence my question: how would you proceed to implement this program flow? Is OOP the way to go? Just to give an initial answer, here is what I've came up until now. There is only one Vehicle class and the various properties/values are handled by the main program (not the class) through a dictionary. However, I'm pretty sure that there must be a more elegant solution (I'm developing using VB.net): Public Class Garage Public GarageAdress As String Private _ListGarageVehicles As New List(Of Vehicles) Public Sub AddVehicle(Vehicle As Vehicles) _ListGarageVehicles.Add(Vehicle) End Sub End Class Public Class Vehicles Public LicensePlateNumber As String Public Enum VehicleTypes Generic = 0 Car = 1 Truck = 2 End Enum Public VehicleType As VehicleTypes Public DictVehicleProperties As New Dictionary(Of String, String) End Class NOTE that in the example above the public/private modifiers do not necessarily reflect the original code

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  • How to make disabled or enabled on check box selection using jquery

    - by kumar
    Hello Friends, I am using this code to make enabling or disabling based on checkbox selection $('#Pchk').change(function() { var che =$('input[name=PMchk]').is(':checked'); if(!che) { $('fieldset').find("input,select,textarea").removeAttr('disabled'); } else { $('fieldset').find("input:not(:checkbox),select,textarea").attr('disabled', 'disabled'); $('#genericfieldset').find("input,select,textarea").removeAttr('disabled'); } }); Here is my Fieldset <fieldset calss="pricingM" id="PricingEditExceptions"> <div class="fiveper"> <label>FM#: <span><%=(null != a) ? Model.Asset.FundmasterSec : null%></span></label> <label>TNT#:<span><%=(null != a) ? Model.Asset.TNTSecurity: null%></span></label> <label>CUSIP#: <span><%=(null != a) ? Model.Asset.CUSIP :null%></span></label> <label>Asset:<span><%=(null != a) ? Model.Asset.AssetClassCode: null%></span></label> <label>Issue:<span><%=(null != a) ? Model.Asset.IssueType: null%></span></label> <label>COQ:<span><%=(null != a) ? Model.Asset.CodeCountryofQuotationName: null%></span></label> <label>CCY:<span><%=(null != a) ? Model.Asset.CurrencyCode: null%></span></label> <label>&nbsp;</label> </div> <div class="fiveper" id="display"> <input id="Pchk" type="checkbox" name="PMchk" value="<%=Model.ExceptionID%>" /> <label>ID#: <span><%=(null != a) ? Model.ExceptionID : 0%></span></label> <label for="ExceptionStatus"> Status: <span id="gui-stat-<%=Model.ExceptionID %>"> <%=Model.LookupCodes["C_EXCPT_STAT"].FirstOrDefault(model => model.Key.Trim().Equals(Model.ExceptionStatus.Trim())).Value%></span> </label> <label for="ResolutionCode"> Resolution: <span> <%=Html.DropDownListFor(model => model.ResolutionCode, new SelectList(Model.LookupCodes["C_EXCPT_RESL"], "Key", "Value", (null != Model.ResolutionCode) ? Model.ResolutionCode.Trim() : Model.ResolutionCode))%> </span> </label> <label for="ReasonCode"> Reason: <span><%=Html.DropDownListFor(model => model.ReasonCode, new SelectList(Model.LookupCodes["C_EXCPT_RSN"], "Key", "Value", (null != Model.ReasonCode) ? Model.ReasonCode.Trim() : Model.ReasonCode))%></span> </label> <label>Action Taken:<span><%=Html.DropDownListFor(model => model.ActionCode, new SelectList(Model.LookupCodes["C_EXCPT_ACT"], "Key", "Value", (null != Model.ActionCode) ? Model.ActionCode.Trim() : Model.ActionCode))%></span></label> <label>&nbsp;</label> </div> <div class="fiveper"> <label>Follow-Up:<span class="datepicker-container"><input type="text" id="exc-flwup-<%=Model.ExceptionID %>" name="exc-flwup-<%=Model.ExceptionID %>" value="<%=Model.FollowupDate %>" /></span></label> <label>Inqurity #: <span><%=Html.EditorFor(model => model.IOL)%></span> </label> <label>&nbsp;</label> <label>Comment: <span> <%=Html.TextAreaFor(model => model.Comment, new { })%> <%=Html.ValidationMessageFor(model => model.Comment)%> </span> </label> </div> <div id="hide" style="display:none"> <label><span><%=Model.Sequence %></span></label> <label><span><%=Model.AssignedId %></span></label> <span id="gui-stat-<%=Model.ExceptionID%>"> <%=Model.LookupCodes["C_EXCPT_STAT"].FirstOrDefault(model => model.Key.Trim().Equals(Model.ExceptionStatus.Trim())).Value%></span> <span>Last Updated:</span> <%=Model.LastUpdateUser.StartsWith("ATPB") ? "SYSTEM" : Model.LastUpdateUser%><br /> <%=Model.LastUpdated%> <% if (DateTime.Now.Date == Model.LastUpdated.Value .Date ) {%> <%=Math.Round((DateTime.Now - (DateTime)Model.LastUpdated).TotalHours, 0)%> hr<%} %> <p> <%=Html.EditorFor(model => model.SequenceDateTimeAsString)%> <%=Html.EditorFor(model => model.AssignedId)%> <span><%=Html.EditorFor(model => model.Origination)%></span> </p> </div> </fieldset> If I selct Four Users this Fieldset result will come in Four boxes....each box having Checkbox..Initially when the page loads I am disabling $('fieldset').find("input:not(:checkbox),select,textarea").attr('disabled','disabled'); ok with my Checkbox Change Funtion I am trying to make Enable or disable my Fieldset.. H here I need to handle Individual Fieldset based on Chekcbox.. right now If I select one check box all Fieldset inpu,select,texarea are making Disabled or Enable.. can anyone tell me how to handle Individual Fieldset on the same page/ thanks

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  • How do you handle domain logic that spans multiple model objects in an ORM?

    - by duality_
    So I know that business logic should be placed in the model. But using an ORM it is not as clear where I should place code that handles multiple objects. E.g. let's say we have a Customer model which has a type of either sporty or posh and we wanted to customer.add_bonus() to every posh customer. Where would we do this? Do we create a new class to handle all this? If yes, where do we put it (alongside all the other model classes, but not subclass it from the ORM?)? I'm currently using django framework in python, so specific suggestions are even more wanted.

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  • One Model to Rule Them All - VS2010 UML, ADO.NET Entity Data Model, and T4

    - by Eric J.
    I worked on a fairly large project a while back where we modeled the classes in Enterprise Architect and generated the (partial) POCO classes (complete with model-driven business rule validations), persistence (NHibernate mapping file) and DDL. Based on certain model attributes we could flag alternate generation strategies or indicate that a particular portion would be entirely hand-coded. There was a good deal of initial investment, but it paid large dividends over the lifetime of a 15 developer, 3 year project. I'm investigating doing something similar with the current Microsoft technology stack. The place I'm stuck is that class modeling is done with the VS 2010 UML tools, but logical data modeling is done with Entity Data Modeler. Is it a reasonable path to use VS 2010 UML as the "single source of truth" and code generate the edmx files based on the class model? That's the inverse of the common path to create the entity model and use a POCO generator to generate classes. However, a good class model can be used to generate much more than just the properties so I tend to view it as a better choice than the entity model.

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  • Turing Model Vs Von Neuman model

    - by Santhosh
    First some background (based on my understanding).. The Von-Neumann architecture describes the stored-program computer where instructions and data are stored in memory and the machine works by changing it's internal state, i.e an instruction operated on some data and modifies the data. So inherently, there is state msintained in the system. The Turing machine architecture works by manipulating symbols on a tape. i.e A tape with infinite number of slots exists, and at any one point in time, the Turing machine is in a particular slot. Based on the symbol read at that slot, the machine change the symbol and move to a different slot. All of this is deterministic. My questions are Is there any relation between these two models (Was the Von Neuman model based on or inspired by the Turing model)? Can we say that Turing model is a superset of Von Newman model? Does functional Programming fit into Turing model. If so how? (I assume FP does not lend itself nicely to the Von Neuman model)

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  • Save object using variable with object name

    - by FBE
    I'm wondering what an easy way is to save an object in R, using a variable objectName with the name of the object to be saved. I want this to easy save objects, with their name in the file name. I tried to use get, but I didn't manage to save the object with it's original object name. Example: If I have the object called "temp", which I want to save in the directory "dataDir". I put the name of the object in the variable "objectName". Attempt 1: objectName<-"temp" save(get(objectName), file=paste(dataDir, objectName, ".RData", sep="")) load(paste(dataDir, objectName, ".RData", sep="")) This didn't work, because R tries to save an object called get(objectName), instead of the result of this call. So I tried the following: Attempt 2: objectName<-"temp" object<-get(objectName) save(object, file=paste(dataDir, objectName, ".RData", sep="")) load(paste(dataDir, objectName, ".RData", sep="")) This obviously didn't work, because R saves the object with name "object", and not with name "temp". After loading I have a copy of "object", instead of "temp". (Yes, with the same contents...but that is not what I want :) ). So I thought it should be something with pointers. So tried the following: Attempt 3: objectName<-"temp" object<<-get(objectName) save(object, file=paste(dataDir, objectName, ".RData", sep="")) load(paste(dataDir, objectName, ".RData", sep="")) Same result as attempt 2. But I'm not sure I'm doing what I think I'm doing. What is the solution for this?

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  • Book Review: Pro SQL Server 2008 Relational Database Design and Implementation

    - by Alexander Kuznetsov
    Investing in proper database design is a very efficient way to cut maintenance costs. If we expect a system to last, we need to make sure it has a good solid foundation - high quality database design. Surely we can and sometimes do cut corners and save on database design to get things done faster. Unfortunately, such cutting corners frequently comes back and bites us: we may end up spending a lot of time solving issues caused by poor design. So, solid understanding of relational database design is...(read more)

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  • What advantages do we have when creating a separate mapping table for two relational tables

    - by Pankaj Upadhyay
    In various open source CMS, I have noticed that there is a separate table for mapping two relational tables. Like for categories and products, there is a separate product_category_mapping table. This table just has a primary key and two foreign keys from the categories and product tables. My question is what are the benefits of this database design rather than just linking the tables directly by defining a foreign key in either table? Is it just matter of convenience?

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  • Going Beyond the Relational Model with Data

    SQL is a powerful tool for querying data, and for aggregating it. However, you can't easily use it to draw inferences, to make predictions, or to tease out subtle correlations. To provide ever more sophisticated inferences to businesses, the race is on to combine the power of the relational model with advanced statistical packages. Both IBM and PostGres are ready with solutions. And SQL Server? Hmm...

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  • Object mapping in objective-c (iphone) from JSON

    - by freshfunk
    For my iPhone app, I'm consuming a RESTful service and getting JSON. I've found libraries to deserialize this into an NSDictionary. However, I'm wondering if there are any libraries to deserialize the JSON/NSDictionary/Property List into my object (an arbitrary one on my side). The java equivalent would be the object-relational mappers although the sort of object mapping I'm looking for is relatively straightforward (simple data types, no complex relationships, etc.). I noticed that Objective-C does have introspection so it seems theoretically possible but I haven't found a library to do it. Or is there a simple way to load an object from an NSDictionary/Property List object that doesn't require modification every time the object changes? For example: { "id" : "user1", "name" : "mister foobar" "age" : 20 } gets loaded into object @interface User : NSObject { NSString *id; NSString *name; int *age; }

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  • Entity framework (1): implement 1 foreign key to multiple tables

    - by Michel
    Hi, i've modeled this: i have an import table, and an import steps table import 1 .. N importsteps Now i have a table importparams, which hold key/value pairs to register all kind of info about the import or the importsteps. So i have modeled a FK in SqlServer which points to the PK of the import table and to the PK of the importsteps table (the ID's for both the import as the importsteps table are guids, so i can query the importparams with either the id from import or from importsteps and get the right importparams). Makes sense a bit? But how can i model this in the EF? I can see it's a bit hard for the EF to model this, because one realtion can point to multiple classes, but is there a way? The workaround normally is just to get all importparams where FK is the ID, but as you know the FK is not available in the EF version 1. I hope you can help me out, michel

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  • How to seperate the model from the view?

    - by geejay
    I have a bunch of model objects. These objects end up being rendered as views (say forms) in a rich client app. I started to annotate the fields in the model objects (Java annotations) with things that let me render them as forms on the fly (e.g displayname, group, page, validvalues). I now realise that the view has crept into the model. How should I seperate the view logic out of the model objects? TECH: Java, Java Annotations, Eclipse RCP

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  • Accessing two sides of a user-user relationship in rails

    - by Lowgain
    Basically, I have a users model in my rails app, and a fanship model, to facilitate the ability for users to become 'fans' of each other. In my user model, I have: has_many :fanships has_many :fanofs, :through => :fanships In my fanship model, I have: belongs_to :user belongs_to :fanof, :class_name => "User", :foreign_key => "fanof_id" My fanship table basically consists of :id, :user_id and :fanof_id. This all works fine, and I can see what users a specific user is a fan of like: <% @user.fanofs.each do |fan| %> #things <% end %> My question is, how can I get a list of the users that are a fan of this specific user? I'd like it if I could just have something like @user.fans, but if that isn't possible what is the most efficient way of going about this? Thanks!

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  • In MVC, why can't a model create a view?

    - by MUY Belgium
    I have a web application written in Perl with a controller, some "views" and some "Models". Each "Model" is corresponding to one "View". The controller (one file) creates an Model object corresponding to each view (view is a CGI argument) then retrieve the view from the module it has just created. Indeed, this should be bad thing but can you argue a bit more about it. My first idea was that since the object "Model" depends upon the "view", then the "model" is actually a view. But also the fact that ALL the cgi parameters are passed to the Model causes the "Model" to become not truelly a view but to loose all interest, since it is only related to the current implementation of the web apps. On other words, that the "Model" keep model but loose its "comprehensiveness" ("Model" is not easily understandable). I'm am quite new in project analysis, so please do not be too harsh. Why is this bad? I have made a prototype with the main structures I have understood of this web application, made as short as possible. #Model.pm package Model; import { # this requires an attribute called "view" # and this require an argument which is the cgi params } ... #View1.pm package View1; ... #Model1.pm package ModelView1 ; base Model; use View1; sub new { my $class = shift; my $arg = shift; Model::DoSomething($arg); $self->view = new View1($arg); ... } #controller.cgi my $model = 0; ... $model = new Model1( cgi_param => params() ); #there is severall models here ... print $model->get_view()->get_html();

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  • Passing null child object from parent object to a partial view

    - by Mike
    I have an object which contains models for my ASP.NET MVC web app. The Model that is being passed into the view has sub models for "gadgets" on that particular view. Each of these sub models gets passed to a partial view (gadget). The problem is when I have a null model in the view model. See example below. View Model: public class FooBarHolder() { public FooBar1 FooBar1 { get; set; } public FooBar2 FooBar2 { get; set; } } We pass FooBarHolder into the view and inside the view we make calls such as <% Html.RenderPartial("Foo", Model.FooBar1); %> <% Html.RenderPartial("Foo2", Model.FooBar2); %> Now say for instance that Model.FooBar2 was null. What I am experiencing from the strongly typed partial view is an error that says "This view expected a model of type FooBar2 but got a model of type FooBarHolder." Why is this happening instead of just passing in a null?

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