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  • django left join with null

    - by SledgehammerPL
    The model: class Product(models.Model): name = models.CharField(max_length = 128) def __unicode__(self): return self.name class Receipt(models.Model): name = models.CharField(max_length=128) components = models.ManyToManyField(Product, through='ReceiptComponent') class Admin: pass def __unicode__(self): return self.name class ReceiptComponent(models.Model): product = models.ForeignKey(Product) receipt = models.ForeignKey(Receipt) quantity = models.FloatField(max_length=9) unit = models.ForeignKey(Unit) def __unicode__(self): return unicode(self.quantity!=0 and self.quantity or '') + ' ' + unicode(self.unit) + ' ' + self.product.genitive The idea: there are a components on stock. I'd like to find out which recipes I can made with components which I have. It's not easy - but possible - I made a SQL view, which gets the solution. But I'm learning python and Django so I'd like to make it Django-style ;D The concept of solution: get the set of recipes which has at last one component: list_of_available_components = ReceiptComponent.objects.filter(product__in=list_of_available_products).distinct() list_of_related_receipts = Receipt.objects.filter(receiptcomponent__in = list_of_available_components).distinct() get recipes (from list_of_related_receipts) which has not at last one component list_of_incomplete_recipes = (SELECT * FROM drinkbook_receiptcomponent LEFT JOIN drinkstore_stock_products USING(product_id) WHERE drinkstore_stock_products.stock_id IS NULL AND receipt_id IN (SELECT receipt_id FROM drinkbook_receiptcomponent JOIN drinkstore_stock_products USING(product_id))) get recipes (from list_of_related_receipts) which are not in "list_of_incomplete_recipes"

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  • PHP MVC Framework Structure

    - by bigstylee
    I am sorry about the amount of code here. I have tried to show enough for understanding while avoiding confusion (I hope). I have included a second copy of the code at Pastebin. (The code does execute without error/notice/warning.) I am currently creating a Content Management System while trying to implement the idea of Model View Controller. I have only recently come across the concept of MVC (within the last week) and trying to implement this into my current project. One of the features of the CMS is dynamic/customisable menu areas and each feature will be represented by a controller. Therefore there will be multiple versions of the Controller Class, each with specific extended functionality. I have looked at a number of tutorials and read some open source solutions to the MVC Framework. I am now trying to create a lightweight solution for my specific requirements. I am not interested in backwards compatibility, I am using PHP 5.3. An advantage of the Base class is not having to use global and can directly access any loaded class using $this->Obj['ClassName']->property/function();. Hoping to get some feedback using the basic structure outlined (with performance in mind). Specifically; a) Have I understood/implemented the concept of MVC correctly? b) Have I understood/implemented Object Orientated techniques with PHP 5 correctly? c) Should the class propertise of Base be static? d) Improvements? Thank you very much in advance! <?php /* A "Super Class" that creates/stores all object instances */ class Base { public static $Obj = array(); // Not sure this is the correct use of the "static" keyword? public static $var; static public function load_class($directory, $class) { echo count(self::$Obj)."\n"; // This does show the array is getting updated and not creating a new array :) if (!isset(self::$Obj[$class]) && !is_object(self::$Obj[$class])) //dont want to load it twice { /* Locate and include the class file based upon name ($class) */ return self::$Obj[$class] = new $class(); } return TRUE; } } /* Loads general configuration objects into the "Super Class" */ class Libraries extends Base { public function __construct(){ $this->load_class('library', 'Database'); $this->load_class('library', 'Session'); self::$var = 'Hello World!'; //testing visibility /* Other general funciton classes */ } } class Database extends Base { /* Connects to the the database and executes all queries */ public function query(){} } class Session extends Base { /* Implements Sessions in database (read/write) */ } /* General functionality of controllers */ abstract class Controller extends Base { protected function load_model($class, $method) { /* Locate and include the model file */ $this->load_class('model', $class); call_user_func(array(self::$Obj[$class], $method)); } protected function load_view($name) { /* Locate and include the view file */ #include('views/'.$name.'.php'); } } abstract class View extends Base { /* ... */ } abstract class Model extends Base { /* ... */ } class News extends Controller { public function index() { /* Displays the 5 most recent News articles and displays with Content Area */ $this->load_model('NewsModel', 'index'); $this->load_view('news', 'index'); echo $this->var; } public function menu() { /* Displays the News Title of the 5 most recent News articles and displays within the Menu Area */ $this->load_model('news/index'); $this->load_view('news/index'); } } class ChatBox extends Controller { /* ... */ } /* Lots of different features extending the controller/view/model class depending upon request and layout */ class NewsModel extends Model { public function index() { echo $this->var; self::$Obj['Database']->query(/*SELECT 5 most recent news articles*/); } public function menu() { /* ... */ } } $Libraries = new Libraries; $controller = 'News'; // Would be determined from Query String $method = 'index'; // Would be determined from Query String $Content = $Libraries->load_class('controller', $controller); //create the controller for the specific page if (in_array($method, get_class_methods($Content))) { call_user_func(array($Content, $method)); } else { die('Bad Request'. $method); } $Content::$var = 'Goodbye World'; echo $Libraries::$var . ' - ' . $Content::$var; ?> /* Ouput */ 0 1 2 3 Goodbye World! - Goodbye World

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  • what is the idea behind scaling an image using lanczos?

    - by banister
    Hi, I'm interested in image scaling algorithms and have implemented the bilinear and bicubic methods. However, I have heard of the lanczos and other more sophisticated methods for even higher quality image scaling and I am very curious how they work. Could someone here explain the basic idea behind scaling an image using lanczos (both upscaling and downscaling) and why it results in higher quality? I do have a background in fourier analysis and have done some signal processing stuff in the past, but not with relation to image processing, so don't be afraid to use terms like "frequency response" and such in your answer :) EDIT: I guess what i really want to know is the concept and theory behind using a convolution filter for interpolation. (Note: i have already read the wikipedia article on lanczos resampling but it didn't have nearly enough detail for me) thanks alot!

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  • IOC - Should util classes with static helper methods be wired up with IOC?

    - by Greg
    Hi, Just trying to still get my head around IOC principles. Q1: Static Methods - Should util classes with static helper methods be wired up with IOC? For example if I have a HttpUtils class with a number of static methods, should I be trying to pass it to other business logic classes via IOC? Follow on questions for this might be: Q2: Singletons - What about things like logging where you may typically get access to it via a Logger.getInstance() type call. Would you normally leave this as is, and NOT use IOC for injecting the logger into business classes that need it? Q3: Static Classes - I haven't really used this concept, but are there any guidelines for how you'd typically handle this if you were moving to an IOC based approach. Thanks in advance.

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  • What is a practical, real world example of the Linked List?

    - by JStims
    I understand the definition of a Linked List, but how can it be represented and related to a common concept or item? For example, inheritance in OOP can be related to automobiles. All (most) automobiles in real life are the essentially same thing; an automobile has an Engine, you can start() it, you can make the car go(), stop() and so on. An automobile would typically have a maximum passenger capacity but it would differ between a Bus and a SportsCar, which are both automobiles. Is there some real life, intuitive example of the plain ole' singly Linked List like we have with inheritance? The typical textbook Linked List example shows a node with an integer and a pointer to the next, and it just doesn't seem very useful. Your input is appreciated.

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  • Which build tool to teach?

    - by Helper Method
    While similiar questions have been asked, this one's focused on which is best/easiest to teach. I'm giving a weekly tutorial at my university focusing on data structures and algorithms. Fromn time to time I introduce tools which may prove helpful in future projects like JUnit, Mercurial, Eclipse etc.. I plan to show them some kind of build tool but I'm not sure which one to choose. I by myself have very little knowledge about build tools, except a little experience in using make. It's more the concept of a build tool I want to show them, not a special tool per se. Which would be the most easiest/future proof/whatever tool to show them? I've read a little bit about Gradle, which looks nice, but so far I think Ant could be a good choice (it's a Java course I'm giving).

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  • How does a programmer think?

    - by Gordon Potter
    This may be a hopelessly vague question. But I am interested to hear whatever logical thought processes people go through when learning a new concept or trying to get their brain around code they might not have ever seen before. Basically, what general steps does one take to to break down problems and what does it take to "get it"? If you were to diagram a flowchart of how your mental process works when you look at code or try to solve a problem what might it look like? What common references, tips, and mental assumptions do you find useful in problem solving? How is this different between different domains? For example in what ways is a web programmer's thought process similar or different from a traditional desktop app developer's process?

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  • Beginner having a problem with classes

    - by David
    I'm working through O'Reilly's "Learning Python" and having a problem with classes. I think I understand the concept, but in practice have stumbled upon this problem. Fron page 88-89: >>> class Worker: def __innit__(self, name, pay): self.name=name self.pay=pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay*=(1.0+percent) Then the book says "Calling the class like a function generates instances of a new type ...etc" and gives this example. bob = Worker('Bob Smith', 50000) This gives me this error: TypeError: this constructor takes no arguments. And then I start muttering profanities. So what am I doing wrong here? Thanks for the help.

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  • Google app engine or Amazin ec2 for Restful services and direct access to datastore

    - by imran
    I'm thinking of building a Restful app on either App engine or ec2 devloped in Java. I'm interested in opinions/experience of using the two options for this. The primary purpose is to create web services to write and retrieve data through a mobile device...basically creating an API for the service I want to create. It seems to me it would be quicker and cheaper in the beginning to go with google app engine using either restlet or grails.But I also think that I could run into problems in the future when I want to so somthing more advanced and might be restricted by app engines environment. I also want to be able to do data analysis on the data in the datastore as well. It seems that with app engine this would be hard as I don't have direct access to the datastore ( in Amazon I could still have access to the underlying db if I go with MySQL ) .

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  • Develop an classic UI or be bold with a newer design?

    - by DeanMc
    Forgive me if this is the wrong place but I am curious as to how other programmers feel about this topic: I am currently working on my portfolio site, it is being designed and built in silverlight 4. I initially started off with a typical stylised e-folio theme much like a standard website in terms of layout and flow. As I work more in the concept stages something has struck me. Am I trying to shoe-horn yesterday into today? What I am talking about is UI expectations. I'm all for clean user interfaces but that does not mean they should not take advantage of new concepts in presentation right? If you where to develop a site in silverlight as your own portfolio piece would you stick to the tried and tested "website" feel or would you try to come up with a UI that is intuitive and complements the technology? I feel that UI discussions are all the more important now that all forms of web development are allowing better methods to engage the user.

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  • Flex4 Application state in a custom component

    - by itarato
    Hi, I'm porting my Flex3 app to Flex4 (FlashBuilder4). I get the whole new state concept, except one thing. In a custom component (separate mxml file) I'm using the main level Application's state. In Flex3 it was: <mx:State name="only_view_mode"> <mx:RemoveChild target="{myComponent.button1}" /> </mx:State> In Flex4 it should be something like that: <mx:State name="only_view_mode" /> and <mx:LinkButton id="button1" excludeFrom="???" /> My question is: how can I access to an Application state from a component? I checked the official reference (http://www.adobe.com/go/learn_flex4_alldocumentation_en) and Google of course but without any success. Thanks in advance

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  • using internationalization on list data

    - by singh
    i am using Struts2 in application. <s:iterator value="listObject"> <s:component template="abc.vm"> <s:param name="text" value="listValue" /> <s:param name="prefix" value="listIndex" /> </s:component> </s:iterator> listValue is a values of list. i am using iterator to traverse the list. now on listValue, i want to put here internationalization concept.so that all the list value can be display based on Locale which store in a list. please suggest!

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  • What is the "owning side" in an ORM mapping?

    - by Yousui
    Hi guys, I'm new to JPA. Now I have a question that what exactly is the owning side mean? I only have a rough idea of it. Can someone give me an explanation with some mapping examples(one to many, one to one, many to one) please? Great thanks. ps, the following text is excerpt from the decription of @OneToOne in java EE 6 documentation. You can see the concept owning side in it. Defines a single-valued association to another entity that has one-to-one multiplicity. It is not normally necessary to specify the associated target entity explicitly since it can usually be inferred from the type of the object being referenced. If the relationship is bidirectional, the non-owning side must use the mappedBy element of the OneToOne annotation to specify the relationship field or property of the owning side.

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  • how to handle solutions/versioning in subversion

    - by Grayson Mitchell
    We are using ankhsvn to check in our .net code, however I have two issues with our setup that I want to resolve. 1\ I thought a key reason to have a tool like svn is that you can rollback to an earlier version of your codebase. If developers are just checking in code, then how can you get version 1.1 (say the current production build), out of subversion? 2\ In VS you have the concept of solutions, many solutions might use the same project. How do I make sure when a developer checks out a solution, they get the appropriate versions of the projects that belong to that solution?

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  • When should I use static methods in a class and what are the benefits?

    - by NAVEED
    I have concept of static variables but what are the benefits of static methods in a class. I have worked on some projects but I did not make a method static. Whenever I need to call a method of a class, I create an object of that class and call the desired method. Static variable in a method holds it's value even when method is executed but accessible only in its containing method but what is the best definition of static method? Is calling the static method without creating object of that class is the only benefit of static method? What is the accessible range for static method? What is the syntax to create and calling static method in php? Thanks

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  • Java: Best practices for turning foreign horror-code into clean API...?

    - by java.is.for.desktop
    Hello, everyone! I have a project (related to graph algorithms). It is written by someone else. The code is horrible: public fields, no getters/setters huge methods, all public some classes have over 20 fields some classes have over 5 constructors (which are also huge) some of those constructors just left many fields null (so I can't make some fields final, because then every second constructor signals errors) methods and classes rely on each other in both directions I have to rewrite this into a clean and understandable API. Problem is: I myself don't understand anything in this code. Please give me hints on analyzing and understanding such code. I was thinking, perhaps, there are tools which perform static code analysis and give me call graphs and things like this.

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  • How to generate makefile targets from variables?

    - by Ketil
    I currently have a makefile to process some data. The makefile gets the inputs to the data processing by sourcing a CONFIG file, which defines the input data in a variable. Currently, I symlink the input files to a local directory, i.e. the makefile contains: tmp/%.txt: tmp ln -fs $(shell echo $(INPUTS) | tr ' ' '\n' | grep $(patsubst tmp/%,%,$@)) $@ This is not terribly elegant, but appears to work. Is there a better way? Basically, given INPUTS = /foo/bar.txt /zot/snarf.txt I would like to be able to have e.g. %.out: %.txt some command As well as targets to merge results depending on all $(INPUT) files. Also, apart from the kludgosity, the makefile doesn't work correctly with -j, something that is crucial for the analysis to complete in reasonable time. I guess that's a bug in GNU make, but any hints welcome.

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  • Magento layout override!

    - by Farid
    Hi, I'm kind of new to the Magento, so forgive me for my stupid question! As I understand the whole concept of Magento is base on overriding the basic components that's are available with in the Magento. So based on my understanding I've decided to update the layout of onepage checkout in Magento. I've created my own layout and in the config file set that my layout updates the checkout module layout. But the problem is it's actually does not update the base layout, it replaces it self with base layout! Should it be act like this or am I wrong?!

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  • How to name an event handler of a private variable in Vb.Net following FxCop rules and Vb.Net standa

    - by SoMoS
    Hello, On one side, in Vb.Net when you add an event handler to an object the created method is named: <NameOfTheObject>_<NameOfTheMethod>. As I like to have consistent syntax I always follow this rule when creating event handlers by hand. On the other side when I create private variables I prefix them with m_ as this is a common thing used by the community, in C# people use to put _ at the beginning of a variable but this is no CLS compliant. At the end, when I create event handlers for events raised by private variables I end with Subs like m_myVariable_MyEvent. Code Analysis (Fx Cop) is complainig about this way of naming because the method does not start with uppercase and because the _, so the question is: What naming standards do you follow when creating event handlers by hand that follow the Fxcop rules if any? Thanks in advance.

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  • Minimizing SQL queries using join with one-to-many relationship

    - by Brian
    So let me preface this by saying that I'm not an SQL wizard by any means. What I want to do is simple as a concept, but has presented me with a small challenge when trying to minimize the amount of database queries I'm performing. Let's say I have a table of departments. Within each department is a list of employees. What is the most efficient way of listing all the departments and which employees are in each department. So for example if I have a department table with: id name 1 sales 2 marketing And a people table with: id department_id name 1 1 Tom 2 1 Bill 3 2 Jessica 4 1 Rachel 5 2 John What is the best way list all departments and all employees for each department like so: Sales Tom Bill Rachel Marketing Jessica John Pretend both tables are actually massive. (I want to avoid getting a list of departments, and then looping through the result and doing an individual query for each department). Think similarly of selecting the statuses/comments in a Facebook-like system, when statuses and comments are stored in separate tables.

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  • Painting to Form then to Printer

    - by jp2code
    I often find myself needing to create custom reports that do NOT work with Crystal Reports or Report Viewer. Often, I hack a DataTable together and dumping that into a DataGridView control. It is never pretty, and printing is difficult. What I need is a class that I can call using the OnPaint event, but I've never sat down and written all of the Pen and Brush commands until now. Painting to the screen and painting to a printer both use the Graphics object, so I want to build a class that I'd pass in the Graphics object, my window bounds (a Rectangle), and some data (in the form of an instance of my class) that I'd use to paint a form or a sheet of paper. That sounds like a great concept! Surely, someone has done something like this before. Does anyone know of a book, a website tutorial, or video that goes into this? If someone wants to write all that out for me here, more power to you - but I'd think that would be too much work.

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  • How to add a field from a 2nd form?

    - by PowerUser
    Hi all. I'm modifying an existing Lotus view to include a field from another form. I first appended a new column and set it to the desired field. However, after I refreshed, the new column was blank even though I know it has data. I then updated the View Selection formula from: SELECT Form = "A" & StatusIndex < "06" to: SELECT (Form = "A"| Form = "B") & StatusIndex < "06" Still no luck. The view is refreshing successfully, but the new field is still blank. What else is there to add this new column to this view? This is my first time experimenting with Lotus, so if I seem to be missing some major concept, I probably am.

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  • What is the best Java numerical method package?

    - by Bob Cross
    I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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  • Structure accessible by attribute name or index options

    - by Bruno DeGoia
    I am very new to Python, and trying to figure out how to create an object that has values that are accessible either by attribute name, or by index. For example, the way os.stat() returns a stat_result or pwd.getpwnam() returns a struct_passwd. In trying to figure it out, I've only come across C implementations of the above types. Nothing specifically in Python. What is the Python native way to create this kind of object? I apologize if this has been widely covered already. In searching for an answer, I must be missing some fundamental concept that is excluding me from finding an answer.

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  • How is Java Platform independent when it needs JVM to run ?

    - by happysoul
    Just started learning Java and I am confused about this whole independent platform thingy. Doesn't independent means that Java code should be able to run on any machine and would need no special software to be installed (JVM in this case has to be present in the machine)? Like, for example, we need to have Turbo C Compiler in order to compile C/C++ source code and then execute it.. The machine has to have the C compiler. guess I am confused..Somebody please explain in simple language or may be direct me to a tutorial that explain things in simple language ? that would be great I am just not getting the concept.

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