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  • Functional programming compared to OOP with classes

    - by luckysmack
    I have been interested in some of the concepts of functional programming lately. I have used OOP for some time now. I can see how I would build a fairly complex app in OOP. Each object would know how to do things that object does. Or anything it's parents class does as well. So I can simply tell Person().speak() to make the person talk. But how do I do similar things in functional programming? I see how functions are first class items. But that function only does one specific thing. Would I simply have a say() method floating around and call it with an equivalent of Person() argument so I know what kind of thing is saying something? So I can see the simple things, just how would I do the comparable of OOP and objects in functional programming, so I can modularize and organize my code base? For reference, my primary experience with OOP is Python, PHP, and some C#. The languages that I am looking at that have functional features are Scala and Haskell. Though I am leaning towards Scala. Basic Example (Python): Animal(object): def say(self, what): print(what) Dog(Animal): def say(self, what): super().say('dog barks: {0}'.format(what)) Cat(Animal): def say(self, what): super().say('cat meows: {0}'.format(what)) dog = Dog() cat = Cat() dog.say('ruff') cat.say('purr')

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  • Law of Demeter confusion [duplicate]

    - by user2158382
    This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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  • At what point should data be sent back to server?

    - by whamsicore
    A good example would be the stackexchange "rate" button. When a post is upvoted the arrow changes color immediately. However there is a grace period for one to edit one's vote decision (oops! voted by mistake?). Is the upvote action processed immediately or does is only process after a set time period, or when the user leaves the page? How exactly is this rating processed? What is the standard for handling dynamic page edits (e.g. stackexchange rating, facebook posts?)

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  • Should all, none, or some overridden methods call Super?

    - by JoJo
    When designing a class, how do you decide when all overridden methods should call super or when none of the overridden methods should call super? Also, is it considered bad practice if your code logic requires a mixture of supered and non-supered methods like the Javascript example below? ChildClass = new Class.create(ParentClass, { /** * @Override */ initialize: function($super) { $super(); this.foo = 99; }, /** * @Override */ methodOne: function($super) { $super(); this.foo++; }, /** * @Override */ methodTwo: function($super) { this.foo--; } }); After delving into the iPhone and Android SDKs, I noticed that super must be called on every overridden method, or else the program will crash because something wouldn't get initialized. When deriving from a template/delegate, none of the methods are supered (obviously). So what exactly are these "je ne sais quoi" qualities that determine whether a all, none, or some overriden methods should call super?

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  • Design Services for the Web

    Advertising and marketing is a huge industry, it spends billions of dollars globally and creates thousands of job opportunities. The advertising and marketing strategies also helped in the evolution ... [Author: Claudia Winifred - Web Design and Development - March 20, 2010]

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  • Strategy to use two different measurement systems in software

    - by Dennis
    I have an application that needs to accept and output values in both US Custom Units and Metric system. Right now the conversion and input and output is a mess. You can only enter in US system, but you can choose the output to be US or Metric, and the code to do the conversions is everywhere. So I want to organize this and put together some simple rules. So I came up with this: Rules user can enter values in either US or Metric, and User Interface will take care of marking this properly All units internally will be stored as US, since the majority of the system already has most of the data stored like that and depends on this. It shouldn't matter I suppose as long as you don't mix unit. All output will be in US or Metric, depending on user selection/choice/preference. In theory this sounds great and seems like a solution. However, one little problem I came across is this: There is some data stored in code or in the database that already returns data like this: 4 x 13/16" screws, which means "four times screws". I need the to be in either US or Metric. Where exactly do I put the conversion code for doing the conversion for this unit? The above already mixing presentation and data, but the data for the field I need to populate is that whole string. I can certainly split it up into the number 4, the 13/16", and the " x " and the " screws", but the question remains... where do I put the conversion code? Different Locations for Conversion Routines 1) Right now the string is in a class where it's produced. I can put conversion code right into that class and it may be a good solution. Except then, I want to be consistent so I will be putting conversion procedures everywhere in the code at-data-source, or right after reading it from the database. The problem though is I think that my code will have to deal with two systems, all throughout the codebase after this, should I do this. 2) According to the rules, my idea was to put it in the view script, aka last change to modify it before it is shown to the user. And it may be the right thing to do, but then it strikes me it may not always be the best solution. (First, it complicates the view script a tad, second, I need to do more work on the data side to split things up more, or do extra parsing, such as in my case above). 3) Another solution is to do this somewhere in the data prep step before the view, aka somewhere in the middle, before the view, but after the data-source. This strikes me as messy and that could be the reason why my codebase is in such a mess right now. It seems that there is no best solution. What do I do?

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  • Java word scramble game [closed]

    - by Dan
    I'm working on code for a word scramble game in Java. I know the code itself is full of bugs right now, but my main focus is getting a vector of strings broken into two separate vectors containing hints and words. The text file that the strings are taken from has a colon separating them. So here is what I have so far. public WordApp() { inputRow = new TextInputBox(); inputRow.setLocation(200,100); phrases = new Vector <String>(FileUtilities.getStrings()); v_hints = new Vector<String>(); v_words = new Vector<String>(); textBox = new TextBox(200,100); textBox.setLocation(200,200); textBox.setText(scrambled + "\n\n Time Left: \t" + seconds/10 + "\n Score: \t" + score); hintBox = new TextBox(200,200); hintBox.setLocation(300,400); hintBox.hide(); Iterator <String> categorize = phrases.iterator(); while(categorize.hasNext()) { int index = phrases.indexOf(":"); String element = categorize.next(); v_words.add(element.substring(0,index)); v_hints.add(element.substring(index +1)); phrases.remove(index); System.out.print(index); } The FileUtilities file was given to us by the pofessor, here it is. import java.util.*; import java.io.*; public class FileUtilities { private static final String FILE_NAME = "javawords.txt"; //------------------ getStrings ------------------------- // // returns a Vector of Strings // Each string is of the form: word:hint // where word contains no spaces. // The words and hints are read from FILE_NAME // // public static Vector<String> getStrings ( ) { Vector<String> words = new Vector<String>(); File file = new File( FILE_NAME ); Scanner scanFile; try { scanFile = new Scanner( file); } catch ( IOException e) { System.err.println( "LineInput Error: " + e.getMessage() ); return null; } while ( scanFile.hasNextLine() ) { // read the word and follow it by a colon String s = scanFile.nextLine().trim().toUpperCase() + ":"; if( s.length()>1 && scanFile.hasNextLine() ) { // append the hint and add to collection s+= scanFile.nextLine().trim(); words.add(s); } } // shuffle Collections.shuffle(words); return words; } }

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  • Do objects maintain identity under all non-cloning conditions in PHP?

    - by Buttle Butkus
    PHP 5.5 I'm doing a bunch of passing around of objects with the assumption that they will all maintain their identities - that any changes made to their states from inside other objects' methods will continue to hold true afterwards. Am I assuming correctly? I will give my basic structure here. class builder { protected $foo_ids = array(); // set in construct protected $foo_collection; protected $bar_ids = array(); // set in construct protected $bar_collection; protected function initFoos() { $this->foo_collection = new FooCollection(); foreach($this->food_ids as $id) { $this->foo_collection->addFoo(new foo($id)); } } protected function initBars() { // same idea as initFoos } protected function wireFoosAndBars(fooCollection $foos, barCollection $bars) { // arguments are passed in using $this->foo_collection and $this->bar_collection foreach($foos as $foo_obj) { // (foo_collection implements IteratorAggregate) $bar_ids = $foo_obj->getAssociatedBarIds(); if(!empty($bar_ids) ) { $bar_collection = new barCollection(); // sub-collection to be a component of each foo foreach($bar_ids as $bar_id) { $bar_collection->addBar(new bar($bar_id)); } $foo_obj->addBarCollection($bar_collection); // now each foo_obj has a collection of bar objects, each of which is also in the main collection. Are they the same objects? } } } } What has me worried is that foreach supposedly works on a copy of its arrays. I want all the $foo and $bar objects to maintain their identities no matter which $collection object they become of a part of. Does that make sense?

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  • Breaking up classes and methods into smaller units

    - by micahhoover
    During code reviews a couple devs have recommended I break up my methods into smaller methods. Their justification was (1) increased readability and (2) the back trace that comes back from production showing the method name is more specific to the line of code that failed. There may have also been some colorful words about functional programming. Additionally I think I may have failed an interview a while back because I didn't give an acceptable answer about when to break things up. My inclination is that when I see a bunch of methods in a class or across a bunch of files, it isn't clear to me how they flow together, and how many times each one gets called. I don't really have a good feel for the linearity of it as quickly just by eye-balling it. The other thing is a lot of people seem to place a premium of organization over content (e.g. 'Look at how organized my sock drawer is!' Me: 'Overall, I think I can get to my socks faster if you count the time it took to organize them'). Our business requirements are not very stable. I'm afraid that if the classes/methods are very granular it will take longer to refactor to requirement changes. I'm not sure how much of a factor this should be. Anyway, computer science is part art / part science, but I'm not sure how much this applies to this issue.

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  • Are injectable classes allowed to have constructor parameters in DI?

    - by Songo
    Given the following code: class ClientClass{ public function print(){ //some code to calculate $inputString $parser= new Parser($inputString); $result= $parser->parse(); } } class Parser{ private $inputString; public __construct($inputString){ $this->inputString=$inputString; } public function parse(){ //some code } } Now the ClientClass has dependency on class Parser. However, if I wanted to use Dependency Injection for unit testing it would cause a problem because now I can't send the input string to the parser constructor like before as its calculated inside ClientCalss itself: class ClientClass{ private $parser; public __construct(Parser $parser){ $this->parser=$parser; } public function print(){ //some code to calculate $inputString $result= $this->parser->parse(); //--> will throw an exception since no string was provided } } The only solution I found was to modify all my classes that took parameters in their constructors to utilize Setters instead (example: setInputString()). However, I think there might be a better solution than this because sometimes modifying existing classes can cause much harm than benefit. So, Are injectable classes not allowed to have input parameters? If a class must take input parameters in its constructor, what would be the way to inject it properly? UPDATE Just for clarification, the problem happens when in my production code I decide to do this: $clientClass= new ClientClass(new Parser($inputString));//--->I have no way to predict $inputString as it is calculated inside `ClientClass` itself. UPDATE 2 Again for clarification, I'm trying to find a general solution to the problem not for this example code only because some of my classes have 2, 3 or 4 parameters in their constructors not only one.

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  • Is OO-programming really as important as hiring companies place it?

    - by ale
    I am just finishing my masters degree (in computing) and applying for jobs.. I've noticed many companies specifically ask for an understanding of object orientation. Popular interview questions are about inheritance, polymorphism, accessors etc. Is OO really that crucial? I even had an interview for a programming job in C and half the interview was OO. In the real world, developing real applications, is object orientation nearly always used? Are key features like polymorphism used A LOT? I think my question comes from one of my weaknesses.. although I know about OO.. I don't seem to be able to incorporate it a great deal into my programs. I would be really interested to get peoples' thoughts on this!

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  • The Advantages of a Professional EBay Store Design

    As the economy continues to struggle, more and more people are looking for ways to bring in more money. Many of them have discovered the income potential that is possible from an EBay store. There ar... [Author: Nathan Busby - Web Design and Development - June 12, 2010]

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  • Paradigms fit for UI programming

    - by Inca
    This is a more specific question (or actually two, but they are related) coming from the comments of OOP technology death where someone stated that OOP is not the right paradigm for GUI programming. Reading the comments there and here I still have the feeling there are things to learn: which programming paradigms are considered good fits and why are they better than others (perhaps with examples to illustrate?) I removed the tk-example from the title and question

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  • Ruby - when to use instance variables vs parameters between methods?

    - by Michael Durrant
    I'm writing several methods that call other methods. To pass the information I have a couple of choices: Pass the information as parameters Set instance variables so that other methods can access them When should I choose one option over the other? It seems that the first option is good as it is very specific about what is being passed. the downside seems to be that a lot of values are being passed around. The second method doesn't require passing all the values around but seems to lead to a lot of magic where methods set instance variables 'somewhere' Should I always be very explicit about gets passed to other methods in the class? Are there exceptions so this?

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  • overriding implemented base class methods

    - by user793468
    I read somewhere that the chain of inheritance breaks when you alter a behavior from derived class. What does "altering a behavior" mean here? Is overriding an already implemented method in base class considered as "altering behavior"? Or, does the author mean altering method signatures and the output? Also, I ready Duplicating code is not a good practice, and its a maintenance nightmare. Again, does overriding an already implemented method in base class considered "Duplicating code"? If not, what would be considered as "Duplicating code"? I

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  • Handling array passed to object at creation

    - by cecilli0n
    When creating my object I pass it an array of a row from my database. (everything in the array we will need, disregarding unnecessary elements at sql query level) When I need to access certain array elements from within my class, I do so like $this->row['element'] However, As I continue development, I sometimes forget what exactly is in this passed array.(this itself doesn't seem good) I am wondering if their is a professional approach to dealing with this, Or am I the only one who has these "I wonder whats in the array" thoughts. One approach to tackling this could be that when we originally pass the array, in the constructor, we assign each element of the array to its own variable, but is this considered professional practice? Additionally by doing this, we could make those variables constants, in a attempt at immutability. Overall I am trying to adhere to good software craftsmanship. Regards.

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  • Fitting an established site into a CI framework

    - by David
    I manage a rather large, feature full nightmare of a site which has no end of feature creep settings/options/etc. Up to now its been coded in a procedural/functional way and would like to move to an OO,MVC setup. I'm quite new to it all but have done alot of research and feel that CodeIgniter is a code choice of framework to use to help quicken the transfer. Before looking at a framework, I started constructing a list of objects to create classes out of: photos users forum topics forums blogs blog posts comments The trouble I have now, is I do understand where these generic/universal objects fall into the CI MVC setup. What is the best way to organise this kind of stuff? These classes can generally be used on multiple models/views/controllers.

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  • Points To Ponder While Going For A Custom Logo Design

    Every organization, whether small or large, go for designing a logo for its business. And in these days and age, with immense competition, it';s hard to get identified and build a strong brand image. ... [Author: Gisselle Gloria - Web Design and Development - October 05, 2009]

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  • PHP OOP: Am i following right way?

    - by sineverba
    I'm learning OOP (PHP). I've realized my own CRUD Class, that performs some kind of queries SQL. Btw, a Gasoline asked us to realize a smart, simple web-app where he can update prices of his gasoline (gasoline, diesel, lpg) and via an API i could recall them and display in his site. So, I did create a new Class Gasoline but it perform some methods of CRUD Class public function getPrezzoBenzina($id) { $prezzo_benzina = $this->distributore->sql('SELECT prezzo_benzina FROM prezzi WHERE id = '.$id); return $prezzo_benzina } And so on (code is pseudocode, just to explain). I could perform all my code only with help of Crud Class... without necessity of Class Gasoline. So, what I'm missing about OOP? Where am I wrong?

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  • Does FP mess up your OOP skills?

    - by bonomo
    I've been learning functional programming in Haskell and F# for awhile and now when I got some skills it gets harder for me to think in OOP way and program in C# and JavaScript. Everything seems to be ass-backwards there with classes, interfaces, objects and I often stare at the screen trying to think of a better way around without using them. This is something that scares me, because I didn't have problems like that before (not knowing that the same stuff can be done in a different way). So I am concerned as I don't want to loose myself as a OOP developer, because this is what I do for living. Is it a normal thing? Shall I rather stop doing FP? How did you manage to cope with it?

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  • A Look at the Difference Between Web Design and Web Development

    Many people are interested in using the Internet to promote their business. Knowing the difference between web design and web development is important because while the terms are often used in place of one another, they are two very different things. Being able to speak with the people who are creating your website and use the proper terms can help reduce misunderstandings and speed up the creation process.

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  • Why setter method when getter method enough in PHP OOP

    - by phphunger
    I am practicing OOP with PHP, and I am struck at setter and getter methods. I can directly access the class properties and methods with getter method then what's the use of setter method? See my example. <?php class MyClass{ public $classVar = "Its a class variable"; public function Getter(){ return $this -> classVar; } } $obj = new MyClass; echo $obj -> Getter(); ?>

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  • Class Versus Struct

    - by Prometheus87
    In C++ and other influenced languages there is a construct called Structure (struct) and we all know the class. Both are capable of holding functions and variables. some differences are 1. Class is given memory in heap and struct is given memory in stack 2. in class variable are private by default and in struct thy are public My question is that struct was somehow abandoned for Class. Why? other that abstraction, a struct can do all the same stuff a class does. Then why abandon it?

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  • Data Structures: What are some common examples of problems where "buffers" come into action?

    - by Dark Templar
    I was just wondering if there were some "standard" examples that everyone uses as a basis for explaining the nature of a problem that requires the use of a buffer. What are some well-known problems in the real world that can see great benefits from using a buffer? Also, a little background or explanation as to why the problem benefits from using a buffer, and how the buffer would be implemented, would be insightful for understanding the concept!

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  • correct way to implement auth/acl in mvc

    - by WiseStrawberry
    I am looking into making a correctly laid out MVC auth/acl system. I think I want the authentication of a user (and the session handling) to be seperate from the ACL system. (I don't know why but this seems a good idea from the things I've read) What does mvc have to do with this question you ask? Because I wish for the application to be well integrated with my acl. An example of a controller (CodeIgniter) <?php class forums extends MX_Controller { $allowed = array('users', 'admin'); $need_login = true; function __construct() { //example of checking if logged in. if($this->auth->logged_in() && $this->auth->is_admin()) { echo "you're logged in!"; } } public function add_topic() { if($this->auth->allowed('add_topic') { //some add topic things. } else { echo 'not allowed to add topic'; } } } ?> My thoughts $this->auth would be autoloaded in the system. I would like to check the $allowed array against the user currently (not) logged in and react accordingly. Is this a good way of doing things? I haven't seen much literature on mvc integration and auth. I want to make things as easy as possible.

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