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  • Creating an interface and swappable implementations in python

    - by Blankman
    Hi, Would it be possible to create a class interface in python and various implementations of the interface. Example: I want to create a class for pop3 access (and all methods etc.). If I go with a commercial component, I want to wrap it to adhere to a contract. In the future, if I want to use another component or code my own, I want to be able to swap things out and not have things very tightly coupled. Possible? I'm new to python.

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  • how to learn a library/framework structure?

    - by fayer
    a lot of people are contributing to open source libraries/frameworks. i wonder how these people learn the structure so that they can contribute? lets take doctrine and symfony as an example. is there a blueprint over these frameworks to give the developers an insight of the structure? or do they just download it and study the code? how does it work? please you contributors, share your learning strategies! thanks

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  • Need help extrapolating Java code

    - by Berlioz
    If anyone familiar with Rebecca Wirfs-Brock, she has a piece of Java code found in her book titled, Object Design: Roles, Responsibilities, and Collaborations. Here is the quote Applying Double Dispatch to a Specific Problem To implement the game Rock, Paper, Scissors we need to write code that determines whether one object “beats” another. The game has nine possible outcomes based on the three kinds of objects. The number of interactions is the cross product of the kinds of objects. Case or switch statements are often governed by the type of data that is being operated on. The object-oriented language equivalent is to base its actions on the class of some other object. In Java, it looks like this Here is the piece of Java code on page 16 ' import java.util.*; import java.lang.*; public class Rock { public static void main(String args[]) { } public static boolean beats(GameObject object) { if (object.getClass.getName().equals("Rock")) { result = false; } else if (object.getClass.getName().equals("Paper")) { result = false; } else if(object.getClass.getName().equals("Scissors")) { result = true; } return result; } }' ===This is not a very good solution. First, the receiver needs to know too much about the argument. Second, there is one of these nested conditional statements in each of the three classes. If new kinds of objects could be added to the game, each of the three classes would have to be modified. Can anyone share with me how to get this "less than optimal" piece of code to work in order to see it 'working'. She proceeds to demonstrate a better way, but I will spare you. Thanks

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  • Javascript: Access the right scope "under" apply(...)

    - by Chau
    This is a very old problem, but I cannot seem to get my head around the other solutions presented here. I have an object function ObjA() { var a = 1; this.methodA = function() { alert(a); } } which is instantiated like var myObjA = new ObjA(); Later on, I assign my methodA as a handler function in an external Javascript Framework, which invokes it using the apply(...) method. When the external framework executes my methodA, this belongs to the framework function invoking my method. Since I cannot change how my method is called, how do I regain access to the private variable a? My research tells me, that closures might be what I'm looking for.

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  • Classes within classes in PHP

    - by Matt
    Can you do this in PHP? I've heard conflicting opinions: Something like: Class bar { function a_function () { echo "hi!"; } } Class foo { public $bar; function __construct() { $this->bar = new bar(); } } $x = new foo(); $x->bar->a_function(); Will this echo "hi!" or not?

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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • Pattern or recommneded refactoring for method

    - by iKode
    I've written a method that looks like this: public TimeSlotList processTimeSlots (DateTime startDT, DateTime endDT, string bookingType, IList<Booking> normalBookings, GCalBookings GCalBookings, List<DateTime> otherApiBookings) { { ..... common process code ...... while (utcTimeSlotStart < endDT) { if (bookingType == "x") { //process normal bookings using IList<Booking> normalBookings } else if (bookingType == "y") { //process google call bookings using GCalBookings GCalBookings } else if (bookingType == "z" { //process other apibookings using List<DateTime> otherApiBookings } } } So I'm calling this from 3 different places, each time passing a different booking type, and each case passing the bookings I'm interested in processing, as well as 2 empty objects that aren't used for this booking type. I'm not able to get bookings all into the same datatype, which would make this easier and each booking type needs to be processed differently, so I'm not sure how I can improve this. Any ideas?

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  • Cannot extend a class located in another file, PHP

    - by NightMICU
    I am trying to set up a class with commonly used tasks, such as preparing strings for input into a database and creating a PDO object. I would like to include this file in other class files and extend those classes to use the common class' code. However, when I place the common class in its own file and include it in the class it will be used in, I receive an error that states the second class cannot be found. For example, if the class name is foo and it is extending bar (the common class, located elsewhere), the error says that foo cannot be found. But if I place the code for class bar in the same file as foo, it works. Here are the classes in question - Common Class abstract class coreFunctions { protected $contentDB; public function __construct() { $this->contentDB = new PDO('mysql:host=localhost;dbname=db', 'username', 'password'); } public function cleanStr($string) { $cleansed = trim($string); $cleansed = stripslashes($cleansed); $cleansed = strip_tags($cleansed); return $cleansed; } } Code from individual class include $_SERVER['DOCUMENT_ROOT'] . '/includes/class.core-functions.php'; $mode = $_POST['mode']; if (isset($mode)) { $gallery = new gallery; switch ($mode) { case 'addAlbum': $gallery->addAlbum($_POST['hash'], $_POST['title'], $_POST['description']); } } class gallery extends coreFunctions { private function directoryPath($string) { $path = trim($string); $path = strtolower($path); $path = preg_replace('/[^ \pL \pN]/', '', $path); $path = preg_replace('[\s+]', '', $path); $path = substr($path, 0, 18); return $path; } public function addAlbum($hash, $title, $description) { $title = $this->cleanStr($title); $description = $this->cleanStr($description); $path = $this->directoryPath($title); if ($title && $description && $hash) { $addAlbum = $this->contentDB->prepare("INSERT INTO gallery_albums (albumHash, albumTitle, albumDescription, albumPath) VALUES (:hash, :title, :description, :path)"); $addAlbum->execute(array('hash' => $hash, 'title' => $title, 'description' => $description, 'path' => $path)); } } } The error when I try it this way is Fatal error: Class 'gallery' not found in /home/opheliad/public_html/admin/photo-gallery/includes/class.admin_photo-gallery.php on line 10

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  • Zend Framework-where do calls to my methods go? Controller of Model?

    - by Joel
    Hi guys, I'm confused about exactly what I should have in my controller and what in my method. Specifically, I have this in the action method: public function upcomingshowsAction() { $gcal = $this->_validateCalendarConnection(); $uncleanedFeedArray = $this->_getCalendarFeed($gcal); $finishedFeedArray = $this->_cleanFeed($uncleanedFeedArray); $this->view->googleArray = $finishedFeedArray; } And then (incorrectly I know), I have my methods still in the bottom of my controller. So what I'm wondering, is for those methods in the upcomingshowsAction method, should all the actual methods just be in one model and then I'd have something like this: public function upcomingshowsAction() { $finishedFeedArray = new Application_Model_calendarModelPage(); $this->view->googleArray = $finishedFeedArray; } And then something like this in the model: class Application_Model_CalendarModelPage { $gcal = $this->_validateCalendarConnection(); $uncleanedFeedArray = $this->_getCalendarFeed($gcal); $finishedFeedArray = $this->_cleanFeed($uncleanedFeedArray); public functions { ... ... ... } } Am I on the right track here? Thanks!

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  • Type hinting and optional attributes in PHP

    - by Álvaro G. Vicario
    I have a class method that deals with dates: public function setAvailability(DateTime $start, DateTime $end){ } Since item availability can have lower limit, upper limit, both or none, I'd like to make setAvailability() accept NULL values as well. However, the NULL constant violates the type hinting: $foo->setAvailability(NULL, $end); triggers: Catchable fatal error: Argument 1 passed to Foo::setAvailability() must be an instance of DateTime, null given And, as far as I know, I cannot have a DateTime instance with no value. (Can I?) For a reason I cannot grasp, this seems to work: public function setAvailability(DateTime $start=NULL, DateTime $end=NULL){ } ... $foo->setAvailability(NULL, $end); But it looks like a hack that works by pure chance. How would you deal with unset dates in PHP classes?

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  • Multiple Inheritance Debates II: according to Stroutroup

    - by asksuperuser
    I know very well about the traditional arguments about why Interface Inheritance is prefered to multiple inheritance, there has been already a post here : http://stackoverflow.com/questions/191691/should-c-include-multiple-inheritance But according to Stroutroup the real reason why Microsoft and Sun decided to get rid off multiple inheritance is that they have vested interest to do so: instead of putting features in the languages, they put in frameworks so that people then become tied to their platform instead of people having the same capability at a language standard level. What do you think ?

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  • frameworks for coding a php library?

    - by ajsie
    there are plenty of frameworks for coding MVC web applications. this time im going to code a library (think of Doctrine or Solr) with a bunch of class files. u just include a bootstrap or a class file and you are ready to use my classes. i have never tried to code a library before and intend to code one for learning purpose so that i can use various design patterns i have learned. are there any great frameworks for this, how i should organize the different class files, where i can put configuration files and so on? tutorials or other information would be great too. thanks

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  • What Patterns Should I Consider For a Html Widget Generator?

    - by DaveDev
    I'm looking to see if I can design a HtmlHelper extension method that will generate the Html for different types of widgets I want to produce. Each different type of widget implements functionality to get and prepare any data it needs to render. Can anyone suggest any patterns I could refer to for approaches to take? I know there are probably frameworks available that will do this for me, but I thought I'd give it a try anyway. Any points of advice? Thanks

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  • can I put my sqlite connection and cursor in a function?

    - by steini
    I was thinking I'd try to make my sqlite db connection a function instead of copy/pasting the ~6 lines needed to connect and execute a query all over the place. I'd like to make it versatile so I can use the same function for create/select/insert/etc... Below is what I have tried. The 'INSERT' and 'CREATE TABLE' queries are working, but if I do a 'SELECT' query, how can I work with the values it fetches outside of the function? Usually I'd like to print the values it fetches and also do other things with them. When I do it like below I get an error Traceback (most recent call last): File "C:\Users\steini\Desktop\py\database\test3.py", line 15, in <module> for row in connection('testdb45.db', "select * from users"): ProgrammingError: Cannot operate on a closed database. So I guess the connection needs to be open so I can get the values from the cursor, but I need to close it so the file isn't always locked. Here's my testing code: import sqlite3 def connection (db, arg): conn = sqlite3.connect(db) conn.execute('pragma foreign_keys = on') cur = conn.cursor() cur.execute(arg) conn.commit() conn.close() return cur connection('testdb.db', "create table users ('user', 'email')") connection('testdb.db', "insert into users ('user', 'email') values ('joey', 'foo@bar')") for row in connection('testdb45.db', "select * from users"): print row How can I make this work?

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  • Why does PHP 5.2 disallow abstract static class methods?

    - by Artem Russakovskii
    After enabling strict warnings in PHP 5.2, I saw a load of strict standards warnings from a project that was originally written without strict warnings: Strict Standards: Static function Program::getSelectSQL() should not be abstract in Program.class.inc The function in question belongs to an abstract parent class Program and is declared abstract static because it should be implemented in its child classes, such as TVProgram. I did find references to this change here: Dropped abstract static class functions. Due to an oversight, PHP 5.0.x and 5.1.x allowed abstract static functions in classes. As of PHP 5.2.x, only interfaces can have them. My question is: can someone explain in a clear way why there shouldn't be an abstract static function in PHP?

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  • Graphic editor opensource project example on c++ underlying composite pattern

    - by G-71
    Can you tell me when I can see a some opensource project (only project on C++ language), which is simple graphic editor, ?ontaining following primitive (for example): an ellipse, a rectangle, a line. And desirable, that to be able to group this primitive in one primitive (for example, Word Grouping - Group). Composite pattern use is desirable in this project. I want to see how to organize classes, but more serious for me is to see how organize grouping operation. I searched for it on codeproject.com codeproject.com, codeplex.com, but not found this. I have already some source http://pastebin.com/xe4JF5PW But in my opinion, this code is dirty and ugly. Therefore, I want to see some opensource project for example. Thanks!

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  • Is it possible to establish default values for inherited fields in subclasses?

    - by Christian Mann
    I'm trying to establish a default value for inherited fields from superclasses. So, my class hierarchy is thus: Character - Enemy - Boss                 \                   - Hero Each Character has a public static char avatar to represent him on an ASCII playing field. How do I set a default value for the avatar of each class inherited from Character? Thank you!

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  • Call static properties within another class in php

    - by ali A
    I have problem about calling a static property of a class inside another class. Class A { public $property; public function __construct( $prop ) { $this->property = $prop; } public function returnValue(){ return static::$this->property; } } Class B extends A { public static $property_one = 'This is first property'; public static $property_two = 'This is second property'; } $B = new B( 'property_one' ); $B->returnValue(); I expect to return This is first property But the Output is just the name a parameter input in __construct; When I print_r( static::$this->property ); the output is just property_one

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  • Who needs singletons?

    - by sexyprout
    Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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  • OO Design: use Properties or Overloaded methods?

    - by Robert Frank
    Question about OO design. Suppose I have a base object vehicle. And two descendants: truck and automobile. Further, suppose the base object has a base method: FixFlatTire(); abstract; When the truck and automobile override the base object's, they require different information from the caller. Am I better off overloading FixFlatTire like this in the two descendant objects: Procedure Truck.FixFlatTire( OfficePhoneNumber: String; NumberOfAxles: Integer): Override; Overload; Procedure Automobile.FixFlatTire( WifesPhoneNumber: String; AAAMembershipID: String): Override; Overload; Or introducing new properties in each of the descendants and then setting them before calling FixFlatTire, like this: Truck.OfficePhoneNumber := '555-555-1212'; Truck.NumberOfAxles := 18; Truck.FixFlatTire(); Automobile.WifesPhoneNumber := '555-555-2323'; Automobile.AAAMembershipID := 'ABC'; Automobile.FixFlatTire();

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  • Java debug error

    - by ivor
    Hello, I wonder if anyone can help - I have this error showing recently when debugging in eclipse - what doe it mean by resource, an imported package or the location of some java files ? Can't find resource for bundle sun.awt.resources.awt, key AWT.EventQueueClass MissingResourceException (id =45) Thanks

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  • Exporting to CSV with dynamic field type handling

    - by serhio
    I have to do an export from DB to CSV. field; fileld; field... etc Have 3 types of fields: Alpha, Numeric and Bool respresented as "alphaValue",intValue and True/False. I try to encapsulate this in a fields collection, in order to export if alpha then set "", if Bool=True/False if numeric let as is. and try to build a CsvField class: Public Structure?Class CsvField(Of T As ???) End Structure Enum FieldType Alpha Bool Numeric End Enum any suggestions welcomed.

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  • exclude private property from print_r or object?

    - by Hailwood
    Basically I am using Code Igniter, and the Code Igniter base class is huge, when I print_r some of my objects they have the base class embedded inside them. this makes it a pain to get the information I actually wanted (the rest of the properties). So, I am wondering if there is a way I can hide, or remove the base class object? I have tried clone $object; unset($object->ci); print_r($object); but of course the ci property is private. the actual function I am using for dumping is: /** * Outputs the given variables with formatting and location. Huge props * out to Phil Sturgeon for this one (http://philsturgeon.co.uk/blog/2010/09/power-dump-php-applications). * To use, pass in any number of variables as arguments. * Optional pass in "true" as final argument to kill script after dump * * @return void */ function dump() { list($callee) = debug_backtrace(); $arguments = func_get_args(); $total_arguments = count($arguments); if (end($arguments) === true) $total_arguments--; echo '<fieldset style="background: #fefefe !important; border:2px red solid; padding:5px">'; echo '<legend style="background:lightgrey; padding:5px;">' . $callee['file'] . ' @ line: ' . $callee['line'] . '</legend><pre>'; $i = 0; foreach ($arguments as $argument) { //if the last argument is true we don't want to display it. if ($i == ($total_arguments) && $argument === true) break; echo '<br/><strong>Debug #' . (++$i) . ' of ' . $total_arguments . '</strong>: '; if ((is_array($argument) || is_object($argument)) && count($argument)) { print_r($argument); } else { var_dump($argument); } } echo '</pre>' . PHP_EOL; echo '</fieldset>' . PHP_EOL; //if the very last argument is "true" then die if (end($arguments) === true) die('Killing Script'); }

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  • Which is the correct design pattern for my PHP application?

    - by user1487141
    I've been struggling to find good way to implement my system which essentially matches the season and episode number of a show from a string, you can see the current working code here: https://github.com/huddy/tvfilename I'm currently rewriting this library and want a nicer way to implement how the the match happens, currently essentially the way it works is: There's a folder with classes in it (called handlers), every handler is a class that implements an interface to ensure a method called match(); exists, this match method uses the regex stored in a property of that handler class (of which there are many) to try and match a season and episode. The class loads all of these handlers by instantiating each one into a array stored in a property, when I want to try and match some strings the method iterates over these objects calling match(); and the first one that returns true is then returned in a result set with the season and episode it matched. I don't really like this way of doing it, it's kind of hacky to me, and I'm hoping a design pattern can help, my ultimate goal is to do this using best practices and I wondered which one I should use? The other problems that exist are: More than one handler could match a string, so they have to be in an order to prevent the more greedy ones matching first, not sure if this is solvable as some of the regex patterns have to be greedy, but possibly a score system, something that shows a percentage of how likely the match is correct, i'd have no idea how to actually implement this though. I'm not if instantiating all those handlers is a good way of doing it, speed is important, but using best practices and sticking to design patterns to create good, extensible and maintainable code is my ultimate priority. It's worth noting the handler classes sometimes do other things than just regex matching, they sometimes prep the string to be matched by removing common words etc. Cheers for any help Billy

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