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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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  • Protecting sensitive entity data

    - by Andreas
    Hi, I'm looking for some advice on architecture for a client/server solution with some peculiarities. The client is a fairly thick one, leaving the server mostly to peristence, concurrency and infrastructure concerns. The server contains a number of entities which contain both sensitive and public information. Think for example that the entities are persons, assume that social security number and name are sensitive and age is publicly viewable. When starting the client, the user is presented with a number of entities, not disclosing any sensitive information. At any time the user can choose to log in and authenticate against the server, given the authentication is successful the user is granted access to the sensitive information. The client is hosting a domain model and I was thinking of implementing this as some kind of "lazy loading", making the first request instantiating the entities and later refreshing them with sensitive data. The entity getters would throw exceptions on sensitive information when they've not been disclosed, f.e.: class PersonImpl : PersonEntity { private bool undisclosed; public override string SocialSecurityNumber { get { if (undisclosed) throw new UndisclosedDataException(); return base.SocialSecurityNumber; } } } Another more friendly approach could be to have a value object indicating that the value is undisclosed. get { if (undisclosed) return undisclosedValue; return base.SocialSecurityNumber; } Some concerns: What if the user logs in and then out, the sensitive data has been loaded but must be disclosed once again. One could argue that this type of functionality belongs within the domain and not some infrastructural implementation(i.e. repository implementations). As always when dealing with a larger number of properties there's a risk that this type of functionality clutters the code Any insights or discussion is appreciated!

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  • Practical refactoring

    - by ahb
    I've read about refactoring and probably did it before I even knew about it, however I don't really know much about it is actually done and what it practically means. What, from your view, is refactoring? How and when do you do it?

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  • Stateless singleton VS Static methods

    - by Sebastien Lorber
    Hey, Don't find any good answer to this simple question about helper/utils classes: Why would i create a singleton (stateless) rather than static methods? Why an object instance could be needed while the object has no state? Sometimes i really don't know what to use...

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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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  • SQL Server (2008) Creating link tables with unique rows

    - by peteski22
    Hi guys, I'm having trouble getting in touch with SQL Server Managemen Studio 2008! I want to create a link-table that will link an Event to many Audiences (EventAudience). An example of the data that could be contained: EventId | AudienceId 4 1 5 1 4 2 However, I don't want this: EventId | AudienceId 4 1 4 1 I've been looking at relationships and constraints.. but no joy so far! As a sneaky second part to the question, I would like to set up the Audience table such that if a row is deleted from Audience, it will clear down the EventAudience link table in a cascading manner. As always, ANY help/advice appreciated! Thanks Pete

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  • Multiple values in a column

    - by Adnan
    Hi I need some advice regarding multiple records. I have a table with fields username,*message* and message_to. the scenario could be of sending same message to multiple users in a go. What do you suggest? will it be efficient to save all recipients in a single column with comma separated values or I add multiple entries ? Thanks /A

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  • Does introducing foreign keys to MySQL reduce performance

    - by Tam
    I'm building Ruby on Rails 2.3.5 app. By default, Ruby on Rails doesn't provide foreign key contraints so I have to do it manually. I was wondering if introducing foreign keys reduces query performance on the database side enough to make it not worth doing. Performance in this case is my first priority as I can check for data consistency with code. What is your recommendation in general? do you recommend using foreign keys? and how do you suggest I should measure this?

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  • Correct handling of return data

    - by Serhiy
    Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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  • Inheritance in XML Schema definition (XSD) for Java objects

    - by bguiz
    Hi, I need to create an XML schema definition (XSD) that describes Java objects. I was wondering how to do this when the objects in question inherit from a common base class with a type parameter. public abstract class Rule<T> { ... } public abstract class TimeRule extends Rule<XTime> { ... } public abstract class LocationRule extends Rule<Location> { ... } public abstract class IntRule extends Rule<Integer> { ... } .... (where XTime and Location are custom classes define elsewhere) How would I go about constructing an XSD that such that I can have XML nodes that represent each of the subclasses of Rule<T> - without the XSD for each of them repeating their common contents? Thank you!

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  • Fastest way to perform subset test operation on a large collection of sets with same domain

    - by niktech
    Assume we have trillions of sets stored somewhere. The domain for each of these sets is the same. It is also finite and discrete. So each set may be stored as a bit field (eg: 0000100111...) of a relatively short length (eg: 1024). That is, bit X in the bitfield indicates whether item X (of 1024 possible items) is included in the given set or not. Now, I want to devise a storage structure and an algorithm to efficiently answer the query: what sets in the data store have set Y as a subset. Set Y itself is not present in the data store and is specified at run time. Now the simplest way to solve this would be to AND the bitfield for set Y with bit fields of every set in the data store one by one, picking the ones whose AND result matches Y's bitfield. How can I speed this up? Is there a tree structure (index) or some smart algorithm that would allow me to perform this query without having to AND every stored set's bitfield? Are there databases that already support such operations on large collections of sets?

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  • Modules vs. Classes and their influence on descendants of ActiveRecord::Base

    - by Chris
    Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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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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  • 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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  • Refactoring Singleton Overuse

    - by drharris
    Today I had an epiphany, and it was that I was doing everything wrong. Some history: I inherited a C# application, which was really just a collection of static methods, a completely procedural mess of C# code. I refactored this the best I knew at the time, bringing in lots of post-college OOP knowledge. To make a long story short, many of the entities in code have turned out to be Singletons. Today I realized I needed 3 new classes, which would each follow the same Singleton pattern to match the rest of the software. If I keep tumbling down this slippery slope, eventually every class in my application will be Singleton, which will really be no logically different from the original group of static methods. I need help on rethinking this. I know about Dependency Injection, and that would generally be the strategy to use in breaking the Singleton curse. However, I have a few specific questions related to this refactoring, and all about best practices for doing so. How acceptable is the use of static variables to encapsulate configuration information? I have a brain block on using static, and I think it is due to an early OO class in college where the professor said static was bad. But, should I have to reconfigure the class every time I access it? When accessing hardware, is it ok to leave a static pointer to the addresses and variables needed, or should I continually perform Open() and Close() operations? Right now I have a single method acting as the controller. Specifically, I continually poll several external instruments (via hardware drivers) for data. Should this type of controller be the way to go, or should I spawn separate threads for each instrument at the program's startup? If the latter, how do I make this object oriented? Should I create classes called InstrumentAListener and InstrumentBListener? Or is there some standard way to approach this? Is there a better way to do global configuration? Right now I simply have Configuration.Instance.Foo sprinkled liberally throughout the code. Almost every class uses it, so perhaps keeping it as a Singleton makes sense. Any thoughts? A lot of my classes are things like SerialPortWriter or DataFileWriter, which must sit around waiting for this data to stream in. Since they are active the entire time, how should I arrange these in order to listen for the events generated when data comes in? Any other resources, books, or comments about how to get away from Singletons and other pattern overuse would be helpful.

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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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  • Connecting data to a GUI - OOP

    - by tau
    I have an application with several graphs and tables on it. I worked fast and just made classes like Graph and Table that each contained a request object (pseudo-code): class Graph { private request; public function setDateRange(dateRange) { request.setDateRange(dateRange); } public function refresh() { request.getData(function() { //refresh the display }); } } Upon a GUI event (say, someone changes the date range dropdown), I'd just call the setters on the Graph instance and then refresh it. Well, when I added other GUI elements like tables and whatnot, they all basically had similar methods (setDateRange and other things common to the request). What are some more elegant OOP ways of doing this? The application is very simple and I don't want to over-architect it, but I also don't want to have a bunch of classes with basically the same methods that are just routing to a request object. I also don't want to set up each GUI class as inheriting from the request class, but I'm open to any ideas really.

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  • Rails architecture questions

    - by justinbach
    I'm building a Rails site that, among other things, allows users to build their own recipe repository. Recipes are entered either manually or via a link to another site (think epicurious, cooks.com, etc). I'm writing scripts that will scrape a recipe from these sites given a link from a user, and so far (legal issues notwithstanding) that part isn't giving me any trouble. However, I'm not sure where to put the code that I'm writing for these scraper scripts. My first thought was to put it in the recipes model, but it seems a bit too involved to go there; would a library or a helper be more appropriate? Also, as I mentioned, I'm building several different scrapers for different food websites. It seems to me that the elegant way to do this would be to define an interface (or abstract base class) that determines a set of methods for constructing a recipe object given a link, but I'm not sure what the best approach would be here, either. How might I build out these OO relationships, and where should the code go?

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  • How it is better to organise a large database of addresses?

    - by shurik2533
    How it is better to organise a large database of addresses? It is need to create mysql database of addresses. How it is better for organising? I have two variants: 1) cuontries id|name 1 |Russia cities id|name 1 |Moscow 2 |Saratov villages id|name streets id|name 1 |Lenin st. places id|name |country_id|city_id|village_id|street_id|building_number|office|flat_number|room_number 1 |somebuilding |1 |1 |NULL |1 |31 |12a |NULL |NULL For simplification I use not all making addresses. If any part does not participate in the address it is equal NULL 2) addressElements id|name 1 |country 2 |city 3 |village 4 |street 5 |office 6 |flat_number 7 |room_number addressValues id|addressElement_id|value 1 |1 |Russia 2 |2 |Saratov 3 |2 |Moscow 4 |3 |Prostokvashino 5 |4 |Lenin st. places id| name 1 | somebuilding places_has_addressValues place_id|addressValue_id 1 |1 1 |3 1 |5 UPD. I have decided to make as follows

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