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  • Are document-oriented databases any more suitable than relational ones for persisting objects?

    - by Owen Fraser-Green
    In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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  • Calling a function within a class

    - by JM4
    I am having trouble calling a specific function within a class. The call is made: case "Mod10": if (!validateCreditCard($fields[$field_name])) $errors[] = $error_message; break; and the class code is: class CreditCardValidationSolution { var $CCVSNumber = ''; var $CCVSNumberLeft = ''; var $CCVSNumberRight = ''; var $CCVSType = ''; var $CCVSError = ''; function validateCreditCard($Number) { $this->CCVSNumber = ''; $this->CCVSNumberLeft = ''; $this->CCVSNumberRight = ''; $this->CCVSType = ''; $this->CCVSError = ''; // Catch malformed input. if (empty($Number) || !is_string($Number)) { $this->CCVSError = $CCVSErrNumberString; return FALSE; } // Ensure number doesn't overrun. $Number = substr($Number, 0, 20); // Remove non-numeric characters. $this->CCVSNumber = preg_replace('/[^0-9]/', '', $Number); // Set up variables. $this->CCVSNumberLeft = substr($this->CCVSNumber, 0, 4); $this->CCVSNumberRight = substr($this->CCVSNumber, -4); $NumberLength = strlen($this->CCVSNumber); $DoChecksum = 'Y'; // Mod10 checksum process... if ($DoChecksum == 'Y') { $Checksum = 0; // Add even digits in even length strings or odd digits in odd length strings. for ($Location = 1 - ($NumberLength % 2); $Location < $NumberLength; $Location += 2) { $Checksum += substr($this->CCVSNumber, $Location, 1); } // Analyze odd digits in even length strings or even digits in odd length strings. for ($Location = ($NumberLength % 2); $Location < $NumberLength; $Location += 2) { $Digit = substr($this->CCVSNumber, $Location, 1) * 2; if ($Digit < 10) { $Checksum += $Digit; } else { $Checksum += $Digit - 9; } } // Checksums not divisible by 10 are bad. if ($Checksum % 10 != 0) { $this->CCVSError = $CCVSErrChecksum; return FALSE; } } return TRUE; } } When I run the application - I get the following message: Fatal error: Call to undefined function validateCreditCard() in C:\xampp\htdocs\validation.php on line 339 any ideas?

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  • function and class to show image not working in php

    - by Gully
    i am trying to get get the following working nothing is happen when i use the function i am trying to get it to display images class ItemRes { //items DB var $img=""; } function ShowItemImage($index,$res_a){ if(sizeof($res_a) > $index){ if($res_a[$index] != NULL) { $cimg = $res_a[$index]->img; return "<img src='$cimg' width='70' height='70' style='cursor:pointer'></img>"; } }else{ return "<center class='whitetxt'><strong>Empty</strong></center>"; } } $res_array = array(); $idx=0; $result21 = mysql_query("SELECT * FROM photos WHERE eid='$eid' ORDER BY id DESC") or die (mysql_error()); while ($row21 = mysql_fetch_array($result21)) { $img_path = $row21['path']; $obj = new ItemRes(); $obj->img = $img_path; $res_array[$idx] = $obj; $idx++; } ShowItemImage(0,$res_array) ShowItemImage(1,$res_array)

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  • Relvance of 'public' contructor in abstract class.

    - by Amby
    Is there any relevance of a 'public' constructor in an abstract class? I can not think of any possible way to use it, in that case shouldn't it be treated as error by compiler (C#, not sure if other languages allow that). Sample Code: internal abstract class Vehicle { public Vehicle() { } } The C# compiler allows this code to compile, while there is no way i can call this contructor from the outside world. It can be called from derived classes only. So shouldn't it allow 'protected' and 'private' modifiers only. Please comment.

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  • Basic class returns onject reference instead of Array

    - by php-b-grader
    I have very basic class: class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; return $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); return $this->customer; } } $customer = new Customer($order->customer->id); print_r($customer); This is not doing what I want it to but I understand why... $customer returns a reference to the Customer Object... But what I want is the MySQL row array from the mysql_fetch_row() call... What am I missing?

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  • Need help with developing a class for my JUnit test

    - by alpdog14
    I have this JUnit test that I need help developing a Interface and Class for, here is the test: Box b1 = new DefaultBox( "abc" ); Box b2 = new DefaultBox( "def" ); Box b3 = new DefaultBox( "" ); assertEquals("abc", b1.contents()); assertEquals("[abc]", b1.toString()); assertTrue(b1.equals(b1)); assertFalse(b1.equals(b2)); assertFalse(b1.equals(null)); assertEquals("cba", b1.flip().contents()); assertEquals("", b3.flip().contents()); can anyone help me in developing a Default box class and a box interface to make these test pass? Any help would be most appreciated.

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  • Assigning a variable of a struct that contains an instance of a class to another variable

    - by xport
    In my understanding, assigning a variable of a struct to another variable of the same type will make a copy. But this rule seems broken as shown on the following figure. Could you explain why this happened? using System; namespace ReferenceInValue { class Inner { public int data; public Inner(int data) { this.data = data; } } struct Outer { public Inner inner; public Outer(int data) { this.inner = new Inner(data); } } class Program { static void Main(string[] args) { Outer p1 = new Outer(1); Outer p2 = p1; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p1.inner.data = 2; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p2.inner.data = 3; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); Console.ReadKey(); } } }

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  • Python grab class in class definition.

    - by epochwolf
    I don't even know how to explain this, so here is the code I'm trying. class Test: type = self.__name__ #self doesn't work, how do I get a reference to Test? class Test2(Test): pass #Test2.type should return "Test2" The reason I'm even trying this is I'm working on creating a base class for an orm I'm using. I want to avoid defining the table name for every model I have. Also knowing what the limits of python is will help me avoid wasting time trying impossible things.

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  • Improve this snippet from a prototype class

    - by seengee
    This is a snippet from a prototype class i am putting together. The scoping workaround feels a little hacky to me, can it be improved or done differently? var myClass = Class.create({ initialize: function() { $('formid').getElements().each(function(el){ $(el).observe("blur", function(){ this.validateEl(el); }.bind(this,el)); },this); }, validateEl: function(el){ // validate $(el) in here... } }); Also, it seems to me that i could be doing something like this for the event observers: $('formid').getElements().invoke("observe","blur" ... Not sure how i would pass the element references in though?

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  • Purpose of Instance Methods vs. Class Methods in Objective-C

    - by qegal
    I have checked out all these questions... Difference Class and Instance Methods Difference between class methods and instance methods? Objective-C: Class vs Instance Methods? ...and all they explain is how instance methods are used on instances of a class and class methods are used with the class name, when a message is sent to a class object. This is helpful, but I'm curious to know why one would use a class method vs. an instance method. I'm fairly new to iOS application development, and usually use class methods, and I feel like I'm doing something wrong. Thanks in advanced!

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  • How can I reuse a base class function in a derived class

    - by Armen Ablak
    Let's say we have these four classes: BinaryTree, SplayTree (which is a sub-class of BinaryTree), BinaryNode and SplayNode (which is a sub-class of BinaryNode). In class BinaryTree I have 2 Find functions, like this bool Find(const T &) const; virtual Node<T> * Find(const T &, Node<T> *) const; and in SplayTree I would like to reuse the second one, because it works in the same way (for example) as in SplayTree, the only thing different is the return type, which is SplayNode. I thought it might be enough if I use this line in SplayTree.cpp using BinaryTree::Find; but it isn't. So, how can I do this?

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  • How to initialize one class from a library?

    - by daemonsvk
    Hi, I have a few classes in the class library (separate assembly). I referenced it to my project and I want to initialize one specific class from that library. I know only its name. All of the classes implements one interface. And here comes the problem. My code so far: using MyLibrary; ... IMyInterface dll = Activator.CreateInstance("MyLibrary", "MyLibrary.NameOfClass") as IMyInterface; But dll is always null. Any ideas? Thanks

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  • Class Library Project VS App_Code - Pros / Cons?

    - by rockinthesixstring
    I currently use the App_Code folder for all of my classes, and for me (for now) it seems to be working just fine. I have however been considering making the switch over to a Class Library Project inside my Solution instead of the App_Code folder. Can anyone tell me the pros and cons of doing this? One thought I had was with regards to testing my web app. If I use a Class Library, do I have to compile it every time I want to tweak/test? Obviously in the App_Code folder I don't have to since all of the Classes compile at runtime.

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  • how to create property of type generic class?

    - by Anish
    public class SelectionList<T> : ObservableCollection<SelectionItem<T>> where T : IComparable<T> { // Code } public class SelectionItem<T> : INotifyPropertyChanged { // Code } I need to create a property which is of the type SelectionList...as follows: public SelectionList<string> Sports { get; set; }. But when I replace string with DataRowView, as public SelectionList<DataRowView> Sports { get; set; }. I am getting error. Please help

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  • Python. Strange class attributes behavior

    - by Eugene
    >>> class Abcd: ... a = '' ... menu = ['a', 'b', 'c'] ... >>> a = Abcd() >>> b = Abcd() >>> a.a = 'a' >>> b.a = 'b' >>> a.a 'a' >>> b.a 'b' It's all correct and each object has own 'a', but... >>> a.menu.pop() 'c' >>> a.menu ['a', 'b'] >>> b.menu ['a', 'b'] How could this happen? And how to use list as class attribute?

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  • Load class based on SDK version

    - by Bostjan
    Is there any way I can load a class based on what version of the OS the phone is running? For example: I made an app which requires 1.6+ Android. Is there a way for me to load one class or the other based on what OS the phone is running? I'm asking this specifically for contacts. The database was changed from 1.6 to 2.0 and the old version doesn't retrieve contacts on the new OS phone. I'd still like to keep my 1.6 requirement, but at the same time I'd like 2.0+ phones to access the contact part of the app. So can I make 2 APIs, somehow pack them with the app and decide on the fly which I choose to import?

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  • Access to an "upper" instance of a class from another instance of a different class

    - by BorrajaX
    Hello everyone! I have a tricky question and probably what I want to do is not even possible but... who knows... Python seems very flexible and powerful... I'd like to know if there's a way to access to the class (or its fields) where an object is instanciated. Let's say I have: def Class1: def __init__(self): self.title = "randomTitle" self.anotherField = float() self.class2Field = Class2() and the class whose type will be the class2Field: def Class2: def __init__(self): self.field1 = "" self.field2 = "" # . . . # I'd like to know if there's a way to access the instance of Class1 from the instance of Class2 that is declared in Class1 (meaning, accessing the fields of Class1 from the variable self.class2Field in that Class1 instance) I know I can always change the init in Class2 to accept a Class1 parameter, but I'd like to know if there's another way of "climbing" through the class hierachy... Thank you very much!

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  • Django model class and custom property

    - by dArignac
    Howdy - today a weird problem occured to me: I have a modle class in Django and added a custom property to it that shall not be saved into the database and therefore is not represent in the models structure: class Category(models.Model): groups = models.ManyToManyField(Group) title = defaultdict() Now, when I'm within the shell or writing a test and I do the following: c1 = Category.objects.create() c1.title['de'] = 'german title' print c1.title['de'] # prints "german title" c2 = Category.objects.create() print c2.title['de'] # prints "german title" <-- WTF? It seems that 'title' is kind of global. If I change title to a simple string it works as expected, so it has to do something with the dict? I also tried setting title as a property: title = property(_title) But that did not work, too. So, how can I solve this? Thank you in advance! enter code here

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  • is counter has certain value inside a class in python

    - by mazlor
    i am learning classes in python and when i was reading the documentation i found this example that i didn't understand : class MyClass: """A simple example class""" def __init__(self): self.data = [] i = 12345 def f(self): return 'hello world' then if we assign : x = MyClass() x.counter = 1 now if we implement while loop : while x.counter < 10: x.counter = x.counter * 2 so the value of x.counter will be : 16 while for example if we have a variable y : y = 1 while y < 1 : y = y *2 then if we look for the value of y we find it 1 so i don't know how is the value of counter became 16 . thanks

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  • Basic class returns object reference instead of Array

    - by php-b-grader
    I have very basic class: class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; return $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); return $this->customer; } } $customer = new Customer($order->customer->id); print_r($customer); This is not doing what I want it to but I understand why... $customer returns a reference to the Customer Object... What I want is the MySQL row array from the mysql_fetch_row() - How do I return the array? What am I missing?

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  • Using pipes inside a class in C++

    - by Paul
    I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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