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  • Storing users in a database

    - by EMcKenna
    Im wondering whats the best way of storing different types of users in my database. I am writing an application that has 4 main user types (admin, school, teacher, student). At the moment I have a table for each of these but i'm not sure thats the best way of storing user information. For instance... Allowing students to PM other student is simple (store sender and receiver student_id) but enabling teachers to PM students requires another table (sender teacher_id, sender student_id). Should all users be stored in one users table with a user_type field? If so, the teacher / student specific information will still have to be stored in another table. users user_id, password_hash, user_type students user_id, student_specific_stuff... teachers user_id, teacher_specific_stuff... How do I stop a user who has a user_type = student from being accidentally being entered into the teachers table (as both have a user_id) Just want to make sure I get the database correct before i go any further. Thanks...

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  • PHP static objects giving a fatal error

    - by Webbo
    I have the following PHP code; <?php component_customer_init(); component_customer_go(); function component_customer_init() { $customer = Customer::getInstance(); $customer->set(1); } function component_customer_go() { $customer = Customer::getInstance(); $customer->get(); } class Customer { public $id; static $class = false; static function getInstance() { if(self::$class == false) { self::$class = new Customer; } else { return self::$class; } } public function set($id) { $this->id = $id; } public function get() { print $this->id; } } ?> I get the following error; Fatal error: Call to a member function set() on a non-object in ....../classes/customer.php on line 9 Can anyone tell me why I get this error? I know this code might look strange, but it's based on a component system that I'm writing for a CMS. The aim is to be able to replace HTML tags in the template e.g.; <!-- component:customer-login --> with; <?php component_customer_login(); ?> I also need to call pre-render methods of the "Customer" class to validate forms before output is made etc. If anyone can think of a better way, please let me know but in the first instance, I'd like to know why I get the "Fatal error" mentioned above. Cheers

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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  • Responsive grid, floated elements move underneath one another when min-width is reached

    - by Francesca
    I'm in the process of creating a responsive site (currently only working on the main content.) I've created two floated divs with percentage based widths. One contains an image which resizes with the browser resizing. The image has a min-width of 100px. Can anyone tell me why when put into a mobile sized width it doesn't drop down? How can I make the image stack underneath the text? JS Fiddle Live site

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  • K-nearest neighbour with closed-loop dimensions

    - by Tomas
    Hi, I've got a K-nearest neighbour problem where some of the dimensions are closed loops. For example one is 'time of day' and I'm matching for similarity so 'very early morning' is close to 'late evening', you can't just make it a linear scale from 'very early morning' at one end to 'late evening' at the other. How can I represent this in the data model? Is there an established way to handle this or a way to work around it?

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  • Can I change class types in a setter with an object-oriented language?

    - by user214626
    Hello, Here is the problem statement : Calling a setter on the object should result in the object to change to an object of a different class, which language can support this ? Ex. I have a class called "Man" (Parent Class), and two children namely "Toddler" and "Old Man", they are its children because they override a behaviour in Man called as walk.( i.e Toddler sometimes walks using both his hands and legs kneeled down and the Old man uses a stick to support himself). The Man class has a attribute called age, I have a setter on Man,say it is called setAge(int ageValue). I have 3 objects, 2 toddlers, 1 old-Man. (The system is up and running,i guess when we say objects it is obvious) .I will make this call, toddler.setAge(80), I expect the toddler to change to an object of type Old Man. Is this possible.Please suggest. Thanks,

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • Function returning a class containing a function returning a class

    - by Scott
    I'm working on an object-oriented Excel add-in to retrieve information from our ERP system's database. Here is an example of a function call: itemDescription = Macola.Item("12345").Description Macola is an instance of a class which takes care of database access. Item() is a function of the Macola class which returns an instance of an ItemMaster class. Description() is a function of the ItemMaster class. This is all working correctly. Items can be be stored in more than one location, so my next step is to do this: quantityOnHand = Macola.Item("12345").Location("A1").QuantityOnHand Location() is a function of the ItemMaster class which returns an instance of the ItemLocation class (well, in theory anyway). QuantityOnHand() is a function of the ItemLocation class. But for some reason, the ItemLocation class is not even being intialized. Public Function Location(inventoryLocation As String) As ItemLocation Set Location = New ItemLocation Location.Item = item_no Location.Code = inventoryLocation End Function In the above sample, the variable item_no is a member variable of the ItemMaster class. Oddly enough, I can successfully instantiate the ItemLocation class outside of the ItemMaster class in a non-class module. Dim test As New ItemLocation test.Item = "12345" test.Code = "A1" quantityOnHand = test.QuantityOnHand Is there some way to make this work the way I want? I'm trying to keep the API as simple as possible. So that it only takes one line of code to retrieve a value.

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  • Why are controls within custom panel (C# winforms) disappearing in designer?

    - by Brandon
    I have been able to create a custom C# winforms control that is basically a panel with a fixed banner (header/footer). I want to base other user controls on this "banner panel". I've gotten past the problem with the designer here. I can successfully add controls to the inner content panel. Everything looks fine while designing. However, when I recompile, the controls I added to the content panel disappear. They are still there (in code) but aren't displayed in the designer. Is there any thing that I need to do to set the drawing order of the controls?

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  • How best can I extract a logical model from a physical DB model

    - by Dean
    We have made substantial changes to our physical DB, now as it is the ne dof the project I would like to abstract a logical model from this, to allow me to generate schemas for both Oracle and SQL Server. Can anyone guide me as to the best way to achieve this. I was hoping TOAD data modeller would help but I can't seem to see any options to do what I require?

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  • How to develop Online Shopping Portal Application using PHP ?

    - by Sarang
    I do not know PHP & I have to develop a Shopping Portal with following Definition : Scenario: Online Shopping Portal XYZ.com wants to create an online shopping portal for managing its registered customers and their shopping. The customers need to register themselves first before they do shopping using the shopping portal. However, everyone, whether registered or not, can view the various products along with the prices listed in the portal. The registered customers, after logging in, are allowed to place order for one or more products from the products listed in the portal. Once the order is placed, the customer gets a reference order number and the order status should be “order in process”. The customers can track their order using the given reference number. The management of XYZ.com should be able to modify the order status of a particular reference order number to “shipped” once the products are shipped to the shipping address entered by the customer at the time of placing the order. The Functionalities required are : Create the interface for the XYZ.com shopping portal using HTML/XHTML and CSS. Implement the client side validations using JavaScript. Create the tables using MySQL. Implement the functionality using the server side scripting language, PHP. Integrate all the above tasks and make the XYZ.com shopping portal functional. How do I develop this application with following proper steps of development ?

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  • Can splitting .MDB files into segments help with stability?

    - by Craig Johnston
    Is this a realistic solution to the problems associated with larger .mdb files: split the large .mdb file into smaller .mdb files have one 'central' .mdb containing links to the tables in the smaller .mdb files How easy would it be to make this change to an .mdb backed VB application? Could the changes to the database be done so that there are no changes required to the front-end application?

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  • What should "Solution Architecture" document describe ?

    - by anjanb
    We're going to build a Solution which includes acquiring data through mobile phones(J2ME) and laptops(browser based data acquisition), uploading the same data to back-end servers(built with J2EE) and then analyzing the same data including generating various types of reports. This solution will include a CMS for building the website and various interfaces for various types of users. I'm to do a "Solutions Architecture" document for the same. What should that document consist of ? Are there any templates (WORD, .ODT, .PDF) ? Any inputs appreciated. Thank you so much,

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  • Sifr Horizontal Menu with LI

    - by Rosaiani
    Hello, I am designing a very simple horizontal menu with sIFR and CSS list. The thing about it is that it assigns a certain width to it that makes texts of different widths´ spacing look weird on screen. I´ve seen a default width and height of a certain amount, but what I need is to make it so that the flash is exactly the size of the text. Has anyone bumped into this issue before? Thanks!

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  • Android 2.1 address bar causes change in viewport dimensions

    - by davehumyo
    Hi, I have a page that has a 100% width and height div in it (all surrounding elements are sized accordingly so that it does actually achieve 100% width and height). Below that div I have a second div with a fixed height. In mobile safari and blackberry everything is fine, when the page loads the dimensions are applied correctly (the top div filling the viewport) and the user can scroll down to reveal the second div. Android 2.1 also applies the dimensions correctly, but with an added quirk; when the user scrolls down and removes the address bar from the page, the dimensions of the div are recalculated to fill the viewport, causing the content to jump. Ideally I would like the dimensions of the div to remain static when the page is scrolled, but remain 100% so that it will fill the viewport regardless of device size or orientation. Does anyone know of any way to disable this recalculation? Thanks for any help you can provide.

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  • Algorithms behind FarmVille Game

    - by Vadi
    What are all the algorithms involved in Farmville game, specifically I am interested in drawing trees that has fruits based on user's activities. I am into a project which has a specific need to draw a tree-type image in SVG. I am not sure how to go about the algorithms to define the tree and based on certain business rules the leafs in the tree grows etc., I think you get the idea. Farmville is just an example I took to explain. Any help is greatly appreciated..

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  • Open closed prinicple, problem

    - by Marcus
    Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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  • What's the most common scenario for Cocoa app setup during first launch?

    - by Eimantas
    I am creating an app and I would like a user to set some obligatory preferences during first app launch. What is the most common scenario to achieve this? Should I set some user defaults to see if the app has been setup? Also - if I determine that the app is being launched for the first time - how should I display "Setup" window? If I load it from the separte xib file - how will I deffer the display of main app window?

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  • PHP Object Oriented Web Application

    - by Sev
    I have a class called "Layout" for the layout of the page, another class called "User" for the user. Every page I create, I instantiate a new Layout. When a user logs in, there is a new User instantiated. How do I get an instance of the layout class to know about the instantiated user? I could also save the entire instance of the User in a session variable. I assume that's a bad idea though. What are the best practices for this?

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  • how to tackle a custom forms database

    - by Neil Hickman
    I'm currently researching a project for the place that I work in. We are trying to create a system that will allow forms to be set up dynamically from a database. My question is what database structure would best suit something like this? I currently have a structure of: forms_form forms_formfields forms_formdata I don't think this is the most appropriate layout for this. Basically to make is make sense I need to be able to make a form within the database that can have infinite fields all customized and have the data when submitted stored in the database.

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