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• Object model design: collections on classes

  - by Luke Puplett

  Hi all, Consider Train.Passengers, what type would you use for Passengers where passengers are not supposed to be added or removed by the consuming code? I'm using .NET Framework, so this discussion would suit .NET, but it could apply to a number of modern languages/frameworks. In the .NET Framework, the List is not supposed to be publicly exposed. There's Collection and ICollection and guidance, which I tend to agree with, is to return the closest concrete type down the inheritance tree, so that'd be Collection since it is already an ICollection. But Collection has read/write semantics and so possibly it should be a ReadOnlyCollection, but its arguably common sense not to alter the contents of a collection that you don't have intimate knowledge about so is it necessary? And it requires extra work internally and can be a pain with (de)serialization. At the extreme ends I could just return Person[] (since LINQ now provides much of the benefits that previously would have been afforded by a more specified collection) or even build a strongly-typed PersonCollection or ReadOnlyPersonCollection! What do you do? Thanks for your time. Luke

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• Circular dependency and object creation when attempting DDD

  - by Matthew

  I have a domain where an Organization has People. Organization Entity public class Organization { private readonly List<Person> _people = new List<Person>(); public Person CreatePerson(string name) { var person = new Person(organization, name); _people.Add(person); return person; } public IEnumerable<Person> People { get { return _people; } } } Person Entity public class Person { public Person(Organization organization, string name) { if (organization == null) { throw new ArgumentNullException("organization"); } Organization = organization; Name = name; } public Organization { get; private set; } public Name { get; private set; } } The rule for this relationship is that a Person must belong to exactly one Organization. The invariants I want to guarantee are: A person must have an organization this is enforced via the Person's constuctor An organization must know of its people this is why the Organization has a CreatePerson method A person must belong to only one organization this is why the organization's people list is not publicly mutable (ignoring the casting to List, maybe ToEnumerable can enforce that, not too concerned about it though) What I want out of this is that if a person is created, that the organization knows about its creation. However, the problem with the model currently is that you are able to create a person without ever adding it to the organizations collection. Here's a failing unit-test to describe my problem [Test] public void AnOrganizationMustKnowOfItsPeople() { var organization = new Organization(); var person = new Person(organization, "Steve McQueen"); CollectionAssert.Contains(organization.People, person); } What is the most idiomatic way to enforce the invariants and the circular relationship?

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• Is functional programming a superset of object oriented?

  - by Jimmy Hoffa

  The more functional programming I do, the more I feel like it adds an extra layer of abstraction that seems like how an onion's layer is- all encompassing of the previous layers. I don't know if this is true so going off the OOP principles I've worked with for years, can anyone explain how functional does or doesn't accurately depict any of them: Encapsulation, Abstraction, Inheritance, Polymorphism I think we can all say, yes it has encapsulation via tuples, or do tuples count technically as fact of "functional programming" or are they just a utility of the language? I know Haskell can meet the "interfaces" requirement, but again not certain if it's method is a fact of functional? I'm guessing that the fact that functors have a mathematical basis you could say those are a definite built in expectation of functional, perhaps? Please, detail how you think functional does or does not fulfill the 4 principles of OOP.

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• Recommended reading for (Object Oriented) application design architecture?

  - by e4rthdog

  In life it doesnt matter if you do one thing for 15 years. You will end up waking one day and asking stuff that are equal to "how do i walk?" :) My specific question is that as a new entrant to C# and OOP i am stepping into many little "details" that need to be addressed. Written a lot of code in VB.NET / cobol / simple php e.t.c surely does not help much into the OOP world... So , even after reading entry level books for C# and watching some videos i recently found out about the "factory model design" for applications. I would appreciate if any of you guys recomment some reading on application design architecture for further reading...

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• Newton Game Dynamics: Making an object not affect another object

  - by Boreal

  I'm going to be using Newton in my networked action game with Mogre. There will be two "types" of physics object: global and local. Global objects will be kept in sync for everybody; these include the players, projectiles, and other gameplay-related objects. Local objects are purely for effect, like ragdolls, debris, and particles. Is there a way to make the global objects affect the local objects without actually getting affected themselves? I'd like debris to bounce off of a tank, but I don't want the tank to respond in any way.

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• Design for object with optional and modifiable attributtes?

  - by Ikuzen

  I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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• Object inheritance and method parameters/return types - Please check my logic

  - by user2368481

  I'm preparing for a test and doing practice questions, this one in particular I am unsure I did correctly: We are given a very simple UML diagram to demonstrate inheritance: I hope this is clear, it shows that W inherits from V and so on: |-----Y V <|----- W<|-----| |-----X<|----Z and this code: public X method1(){....} method2(new Y()); method2(method1()); method2(method3()); The questions and my answers: Q: What types of objects could method1 actually return? A: X and Z, since the method definition includes X as the return type and since Z is a kind of X is would be OK to return either. Q: What could the parameter type of method2 be? A: Since method2 in the code accepts Y, X and Z (as the return from method1), the parameter type must be either V or W, as Y,X and Z inherit from both of these. Q: What could return type of method3 be? A: Return type of method3 must be V or W as this would be consistent with answer 2.

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• Tips about how to spread Object Oriented practices

  - by Augusto

  I work for a medium company that has around 250 developers. Unfortunately, lots of them are stuck in a procedural way of thinking and some teams constantly deliver big Transactional Script applications, when in fact the application contains rich logic. They also fail to manage the design dependencies, and end up with services which depend on another large number of services (a clean example of Big Ball of Mud). My question is: Can you suggest how to spread this type of knowledge? I know that the surface of the problem is that these applications have a poor architecture and design. Another issue is that there are some developers who are against writing any kind of test. A few things I'm doing to change this (but I'm either failing or the change is too small are) Running presentations about design principles (SOLID, clean code, etc). Workshops about TDD and BDD. Coaching teams (this includes using sonar, findbugs, jdepend and other tools). IDE & Refactoring talks. A few things I'm thinking to do in the future (but I'm concern that they might not be good) Form a team of OO evangelists, who disseminate an OO way of thinking in differet teams (these people would need to change teams every few months). Running design review sessions, to criticise the design and suggest improvements (even if the improvements are not done because of time constraints, I think this might be useful) . Something I found with the teams I coach, is that as soon as I leave them, they revert back to the old practices. I know I don't spend a lot of time with them, usually just one month. So whatever I'm doing, it doesn't stick. I'm sorry this question is spattered with frustration, but the alterative to write this was to hit my head on the wall until I pass out.

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• Object construction design

  - by James

  I recently started to use c# to interface with a database, and there was one part of the process that appeared odd to me. When creating a SqlCommand, the method I was lead to took the form: SqlCommand myCommand = new SqlCommand("Command String", myConnection); Coming from a Java background, I was expecting something more similar to SqlCommand myCommand = myConnection.createCommand("Command String"); I am asking, in terms of design, what is the difference between the two? The phrase "single responsibility" has been used to suggest that a connection should not be responsible for creating SqlCommands, but I would also say that, in my mind, the difference between the two is partly a mental one of the difference between a connection executing a command and a command acting on a connection, the latter of which seems less like what I have been lead to believe OOP should be. There is also a part of me wondering if the two should be completely separate, and should only come together in some sort of connection.execute(command) method. Can anyone help clear up these differences? Are any of these methods "more correct" than the others from an OO point of view? (P.S. the fact that c# is used is completely irrelevant. It just highlighted to me that different approaches were used)

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• Using visitor pattern with large object hierarchy

  - by T. Fabre

  Context I've been using with a hierarchy of objects (an expression tree) a "pseudo" visitor pattern (pseudo, as in it does not use double dispatch) : public interface MyInterface { void Accept(SomeClass operationClass); } public class MyImpl : MyInterface { public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } } This design was, however questionnable, pretty comfortable since the number of implementations of MyInterface is significant (~50 or more) and I didn't need to add extra operations. Each implementation is unique (it's a different expression or operator), and some are composites (ie, operator nodes that will contain other operator/leaf nodes). Traversal is currently performed by calling the Accept operation on the root node of the tree, which in turns calls Accept on each of its child nodes, which in turn... and so on... But the time has come where I need to add a new operation, such as pretty printing : public class MyImpl : MyInterface { // Property does not come from MyInterface public string SomeProperty { get; set; } public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } public void Accept(SomePrettyPrinter printer) { printer.PrettyPrint(this.SomeProperty); } } I basically see two options : Keep the same design, adding a new method for my operation to each derived class, at the expense of maintainibility (not an option, IMHO) Use the "true" Visitor pattern, at the expense of extensibility (not an option, as I expect to have more implementations coming along the way...), with about 50+ overloads of the Visit method, each one matching a specific implementation ? Question Would you recommand using the Visitor pattern ? Is there any other pattern that could help solve this issue ?

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• Object desing problem for simple school application

  - by Aragornx

  I want to create simple school application that provides grades,notes,presence,etc. for students,teachers and parents. I'm trying to design objects for this problem and I'm little bit confused - because I'm not very experienced in class designing. Some of my present objects are : class PersonalData() { private String name; private String surename; private Calendar dateOfBirth; [...] } class Person { private PersonalData personalData; } class User extends Person { private String login; private char[] password; } class Student extends Person { private ArrayList<Counselor> counselors = new ArrayList<>(); } class Counselor extends Person { private ArrayList<Student> children = new ArrayList<>(); } class Teacher extends Person { private ArrayList<ChoolClass> schoolClasses = new ArrayList<>(); private ArrayList<Subject> subjects = new ArrayList<>(); } This is of course a general idea. But I'm sure it's not the best way. For example I want that one person could be a Teacher and also a Parent(Counselor) and present approach makes me to have two Person objects. I want that user after successful logging in get all roles that it has (Student or Teacher or (Teacher & Parent) ). I think I should make and use some interfaces but I'm not sure how to do this right. Maybe like this: interface Role { } interface TeacherRole implements Role { void addGrade( Student student, Grade grade, [...] ); } class Teacher implements TeacherRole { private Person person; [...] } class User extends Person{ ArrayList<Role> roles = new ArrayList<>(); } Please if anyone could help me to make this right or maybe just point me to some literature/article that covers practical objects design.

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• SOA design principles with regards to database relationships

  - by Eitan

  If I were to extricate my current membership provider from my solution, i.e. as a dll and expose it as a web service with it's own db, how would I model the relationships with regards to SOA design. For example I have a table: USER id, name, lastname, username, password, role. and table PRODUCT id, name, price, createdate, userid the foreign key being userid to table user. How would I model the relationship and/or query the db. If I wanted to get all products that were uploaded today for example, before I would query: SELECT u.name, u.lastname, u.username, p.* FROM PRODUCT p INNER JOIN USER u ON p.userid = u.id WHERE createdate = '05/05/2010' Now that I don't have the table within the database how would I perform this query? Thanks.

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• SQL SERVER – Error: Fix – Msg 208 – Invalid object name ‘dbo.backupset’ – Invalid object name ‘dbo.backupfile’

  - by pinaldave

  Just a day before I got a very interesting email. Here is the email (modified a bit to make it relevant to this blog post). “Pinal, We are facing a very strange issue. One of our query  related to backup files and backup set has stopped working suddenly in SSMS. It works fine in application where we have and in the stored procedure but when we have it in our SSMS it gives following error. Msg 208, Level 16, State 1, Line 1 Invalid object name ‘dbo.backupfile’. Here are our queries which we are trying to execute. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; This query gives us details related to backupset and backup files when the backup was taken.” When I receive this kind of email, usually I have no answers directly. The claim that it works in stored procedure and in application but not in SSMS gives me no real data. I have requested him to very first check following two things: If he is connected to correct server? His answer was yes. If he has enough permissions? His answer was he was logged in as an admin. This means there was something more to it and I requested him to send me a screenshot of the his SSMS. He promptly sends that to me and as soon as I receive the screen shot I knew what was going on. Before I say anything take a look at the screenshot yourself and see if you can figure out why his queries are not working in SSMS. Just to make your life a bit easy, I have already given a hint in the image. The answer is very simple, the context of the database is master database. To execute above two queries the context of the database has to be msdb. Tables backupset and backupfile belong to the database msdb only. Here are two workaround or solution to above problem: 1) Change context to MSDB Above two queries when they will run as following they will not error out and will give the accurate desired result. USE msdb GO SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; 2) Prefix the query with msdb There are cases above script used in stored procedure or part of big query, it is not possible to change the context of the whole query to any specific database. Use three part naming convention and prefix them with msdb. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM msdb.dbo.backupset; SELECT logical_name, backup_size, file_type FROM msdb.dbo.backupfile; Very simple solution but sometime keeps people wondering for an answer. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• PERT shows relationships between defined tasks in a project without taking into consideration a time line

  The program evaluation and review technique (PERT) shows relationships between defined tasks in a project without taking into consideration a time line. This chart is an excellent way to identify dependencies of tasks based on other tasks. This chart allows project managers to identify the critical path of a project to minimize any time delays to the project. According to Craig Borysowich in his article “Pros & Cons of the PERT/CPM Method stated the following advantages and disadvantages: “PERT/CPM has the following advantages: A PERT/CPM chart explicitly defines and makes visible dependencies (precedence relationships) between the WBS elements, PERT/CPM facilitates identification of the critical path and makes this visible, PERT/CPM facilitates identification of early start, late start, and slack for each activity, PERT/CPM provides for potentially reduced project duration due to better understanding of dependencies leading to improved overlapping of activities and tasks where feasible.  PERT/CPM has the following disadvantages: There can be potentially hundreds or thousands of activities and individual dependency relationships, The network charts tend to be large and unwieldy requiring several pages to print and requiring special size paper, The lack of a timeframe on most PERT/CPM charts makes it harder to show status although colors can help (e.g., specific color for completed nodes), When the PERT/CPM charts become unwieldy, they are no longer used to manage the project.” (Borysowich, 2008) Traditionally PERT charts are used in the initial planning of a project like in a project that is utilizing the waterfall approach. Once the chart was created then project managers could further analyze this data to determine the earliest start time for each stage in the project. This is important because this information can be used to help forecast resource needs during a project and where in the project. However, the agile environment can approach this differently because of their constant need to be in contact with the client and the other stakeholders.  The PERT chart can also be used during project iteration to determine what is to be worked on next, such as a prioritized To-Do list a wife would give her husband at the start of a weekend. In my personal opinion, the COTS-centric environment would not really change how a company uses a PERT chart in their day to day work. The only thing I can is that there would be less tasks to include in the chart because the functionally milestones are already completed when the components are purchased. References: http://www.netmba.com/operations/project/pert/ http://web2.concordia.ca/Quality/tools/20pertchart.pdf http://it.toolbox.com/blogs/enterprise-solutions/pros-cons-of-the-pertcpm-method-22221

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• Mapping Object Relationships - QuickStart with NHibernate (Part 3)

  - by BobPalmer

  For this third tutorial, we'll be introducing users new to NHibernat to basic object relationships, starting with a simple many-to-one relationship.  I decided that it would make sense to at least get the readers through some basic relationship mapping (including varieties of parent/child and many to many relationships) before diverging into UI, since most folks are looking for enough to bootstrap themsevles into using NHibernate, and this almost always means some kind of relation between their objects. You can find a link to the article at: http://docs.google.com/Doc?docid=0AUP-rKyyUMKhZGczejdxeHZfMjJmM3c3M3Bnbg&hl=en As always, comments, corrections, and suggestions are appreciated! -Bob

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• How to make an object stay relative to another object

  - by Nick

  In the following example there is a guy and a boat. They have both a position, orientation and velocity. The guy is standing on the shore and would like to board. He changes his position so he is now standing on the boat. The boat changes velocity and orientation and heads off. My character however has a velocity of 0,0,0 but I would like him to stay onboard. When I move my character around, I would like to move as if the boat was the ground I was standing on. How do keep my character aligned properly with the boat? It is exactly like in World Of Warcraft, when you board a boat or zeppelin. This is my physics code for the guy and boat: this.velocity.addSelf(acceleration.multiplyScalar(dTime)); this.position.addSelf(this.velocity.clone().multiplyScalar(dTime)); The guy already has a reference to the boat he's standing on, and thus knows the boat's position, velocity, orientation (even matrices or quaternions can be used).

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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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• Do ORMs normally allow circular relations? If so, how would they handle it?

  - by SeanJA

  I was hacking around trying to make a basic orm that has support for the one => one and one => many relationships. I think I succeeded somewhat, but I am curious about how to handle circular relationships. Say you had something like this: user::hasOne('car'); car::hasMany('wheels'); car::property('type'); wheel::hasOne('car'); You could then do this (theoretically): $u = new user(); echo $u->car->wheels[0]->car->wheels[1]->car->wheels[2]->car->wheels[3]->type; #=> "monster truck" Now, I am not sure why you would want to do this. It seems like it wastes a whole pile of memory and time just to get to something that could have been done in a much shorter way. In my small ORM, I now have 4 copies of the wheel class, and 4 copies of the car class in memory, which causes a problem if I update one of them and save it back to the database, the rest get out of date, and could overwrite the changes that were already made. How do other ORMs handle circular references? Do they even allow it? Do they go back up the tree and create a pointer to one of the parents? DO they let the coder shoot themselves in the foot if they are silly enough to go around in circles?

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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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• 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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• what is an abstract data type in object oriented programming?

  - by sevugarajan

  what is an abstract data type in object oriented programming? I gone through wiki.But i dint get cleared.Please make me clear

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• What is the difference between a Instance and a Object?

  - by streetparade

  What is the Difference between a Instance and a Object? Is there a difference or not?

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• Telerik Object reference not set to an instance of an object

  - by Duncan

  Hi, I have a main form which contains multiple worker threads. These threads raise events which update Telerik controls on the main form. The event handlers contain code which check if InvokeRequired and BeginInvoke where required. At random interval I am receiving the following exception, and have no idea on how where to find this? I was wondering if the following is understandable to anyone to point me in the right direction. Thanks in advance System.Reflection.TargetInvocationException was unhandled Message="Exception has been thrown by the target of an invocation." Source="mscorlib" StackTrace: at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Delegate.DynamicInvokeImpl(Object[] args) at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme) at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme) at System.Windows.Forms.Control.InvokeMarshaledCallbacks() at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ScrollableControl.WndProc(Message& m) at Telerik.WinControls.RadControl.WndProc(Message& m) at Telerik.WinControls.UI.RadStatusStrip.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.Run(ApplicationContext context) at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine) at MyFX.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: System.NullReferenceException Message="Object reference not set to an instance of an object." Source="Telerik.WinControls" StackTrace: at Telerik.WinControls.Layouts.ContextLayoutManager.LayoutQueue.RemoveOrphans(RadElement parent) at Telerik.WinControls.Layouts.ContextLayoutManager.LayoutQueue.Add(RadElement e) at Telerik.WinControls.RadElement.InvalidateArrange(Boolean recursive) at Telerik.WinControls.RadElement.InvalidateArrange() at Telerik.WinControls.RadElement.Measure(SizeF availableSize) at Telerik.WinControls.Layouts.ImageAndTextLayoutPanel.MeasureOverride(SizeF availableSize) at Telerik.WinControls.RadElement.MeasureCore(SizeF availableSize) at Telerik.WinControls.RadElement.Measure(SizeF availableSize) at Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayout() at Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayoutCallback(ILayoutManager manager)

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• Why did object-oriented paradigms take so long to go mainstream?

  - by Earlz

  I read this question and it got me thinking about another fairly recent thing. Object oriented languages. I'm not sure when the first one was created, but why did it take so long before they became mainstream? C became vastly popular, but didn't become the object-oriented C++ for years(decades?) later No mainstream language before the 90s was object oriented Object oriented really seemed to take off with Java and C++ around the same time Now, my question, why did this take so long? Why wasn't C originally conceived as an object-oriented language? Taking a very small subset of C++ wouldn't have affected the core language a whole lot, so why was this idea not popular until the 90s?

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