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• May I give a single class multiple responsibilities if only one will ever be reusable?

  - by lnluis

  To the extent that I understand the Single Responsibility Principle, a SINGLE class must only have one responsibility. We use this so that we can reuse other functionalities in other classes and not affect the whole class. My question is: what if the entity has only one purpose that really interacts with the system, and that purpose won't change? Do you have to separate the implementations of your methods into another class and just instantiate those from your entity class? Or to put it another way... Is it ok to break the SRP if you know those functions will not be reusable in the future? Or is it better to assume that we do not know if the functionalities of these methods will be reusable or not, and so just abstract them to other classes?

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• Is wrapping a third party code the only solution to unit test its consumers? [closed]

  - by Songo

  I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Now some people argue that if a library is stable enough and won't change often then there is no need to wrap it. So assuming that Zend_Mail is stable and won't change and it fits my needs entirely, then I won't need a wrapper for it. Now take a look at my class Logger that depends on Zend_Mail: class Logger{ private $mailer; function __construct(Zend_Mail $mail){ $this->mail=$mail; } function toBeTestedFunction(){ //Some code $this->mail->setTo('some value'); $this->mail->setSubject('some value'); $this->mail->setBody('some value'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Now is wrapping Zend_Mail the only solution or is there a better approach to this problem? The code is in PHP, but answers doesn't have to be. This is more of a design issue than a language specific feature

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• Clarify the Single Responsibility Principle.

  - by dsimcha

  The Single Responsibility Principle states that a class should do one and only one thing. Some cases are pretty clear cut. Others, though, are difficult because what looks like "one thing" when viewed at a given level of abstraction may be multiple things when viewed at a lower level. I also fear that if the Single Responsibility Principle is honored at the lower levels, excessively decoupled, verbose ravioli code, where more lines are spent creating tiny classes for everything and plumbing information around than actually solving the problem at hand, can result. How would you describe what "one thing" means? What are some concrete signs that a class really does more than "one thing"?

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• Non-object-oriented game tutorials

  - by Arcadian

  I've been tasked with writing an essay extolling the virtues of object oriented programming and creating an accompanying game to demonstrate them. My initial idea is to find a tutorial for a simple game written in a programming language which does not follow the OOP paradigm (or written in an OOP language but not in an OOP way) and recreate it in an OOP way using either C# or Java (haven't yet decided). This would then allow me to make concrete comparisons between the two. The game doesn't have to be anything complex; Tetris, Pong, etc. that sort of thing. The problem I've had so far is finding a suitable tutorial, any suggestions?

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• should singleton be life-time available or should it be destroyable?

  - by Manoj R

  Should the singleton be designed so that it can be created and destroyed at any time in program or should it be created so that it is available in life-time of program. Which one is best practice? What are the advantages and disadvantages of both? EDIT :- As per the link shared by Mat, the singleton should be static. But then what are the disadvantages of making it destroyable? One advantage is it memory can be saved when it is not useful.

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• Forwarding data between two interfaces

  - by user84471

  I installed Ubuntu server 12.04 after that I installed dhcp3-server and configured it like this: At isc-dhcp-server INTERFACES="eth0" And in dhcpd.conf # A slightly different configuration for an internal subnet. subnet 192.168.1.0 netmask 255.255.255.0 { range 192.168.1.5 192.168.1.100; option domain-name-servers 192.168.1.1; option domain-name "nazwa.local"; option routers 192.168.1.1; option broadcast-address 192.168.1.255; default-lease-time 600; max-lease-time 7200; } Also I have two eth interfaces: # second netowrk interface auto eth0 iface eth0 inet static address 192.168.1.1 netmask 255.255.255.0 # The primary network interface auto eth1 iface eth1 inet dhcp When I plug computer to eth0 I get propertly ip adress but I can't visit any sites. I do even this: echo 1 > /proc/sys/net/ipv4/ip_forward

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• Figuring out the Call chain

  - by BDotA

  Let's say I have an assemblyA that has a method which creates an instance of assemblyB and calls its MethodFoo(). Now assemblyB also creates an instance of assemblyC and calls MethodFoo(). So no matter if I start with assemblyB in the code flow or with assemlyA, at the end we are calling that MethodFoo of AssemblyC(). My question is when I am in the MethodFoo() how can I know who has called me? Has it been a call originally from assemblyA or was it from assemlyB? Is there any design pattern or a good OO way of solving this?

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• Is this a pattern? Proxy/delegation of interface to existing concrete implementation

  - by Ian Newson

  I occasionally write code like this when I want to replace small parts of an existing implementation: public interface IFoo { void Bar(); } public class Foo : IFoo { public void Bar() { } } public class ProxyFoo : IFoo { private IFoo _Implementation; public ProxyFoo(IFoo implementation) { this._Implementation = implementation; } #region IFoo Members public void Bar() { this._Implementation.Bar(); } #endregion } This is a much smaller example than the real life cases in which I've used this pattern, but if implementing an existing interface or abstract class would require lots of code, most of which is already written, but I need to change a small part of the behaviour, then I will use this pattern. Is this a pattern or an anti pattern? If so, does it have a name and are there any well known pros and cons to this approach? Is there a better way to achieve the same result? Rewriting the interfaces and/or the concrete implementation is not normally an option as it will be provided by a third party library.

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• best practice for initializing class members in php

  - by rgvcorley

  I have lots of code like this in my constructors:- function __construct($params) { $this->property = isset($params['property']) ? $params['property'] : default_val; } Is it better to do this rather than specify the default value in the property definition? i.e. public $property = default_val? Sometimes there is logic for the default value, and some default values are taken from other properties, which was why I was doing this in the constructor. Should I be using setters so all the logic for default values is separated?

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• Two divs, one fixed width, the other, the rest

  - by Shamil

  I've got two div containers. Whilst one needs to be a specific width, I need to adjust it, so that, the other div takes up the rest of the space. Is there any way I can do this? <div class="left"></div> <div class="right"></div> // needs to be 250px .left { float: left; width: 83%; display: table-cell; vertical-align: middle; min-height: 50px; margin-right: 10px; overflow: auto } .right { float: right; width: 16%; text-align: right; display: table-cell; vertical-align: middle; min-height: 50px; height: 100%; overflow: auto } Thanks

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• Best practice to collect information from child objects

  - by Markus

  I'm regularly seeing the following pattern: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new StuffCollection(); foreach(child c : children) c.AddRequiredStuff(collection); // do something with the collection ... } public abstract void AddRequiredStuff(StuffCollection collection); } public class ConcreteItem : BaseItem { // ... public override void AddRequiredStuff(StuffCollection collection) { Stuff stuff; // ... collection.Add(stuff); } } Where I would use something like this, for better information hiding: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new StuffCollection(); foreach(child c : children) collection.AddRange(c.RequiredStuff()); // do something with the collection ... } public abstract StuffCollection RequiredStuff(); } public class ConcreteItem : BaseItem { // ... public override StuffCollection RequiredStuff() { StuffCollection stuffCollection; Stuff stuff; // ... stuffCollection.Add(stuff); return stuffCollection; } } What are pros and cons of each solution? For me, giving the implementation access to parent's information is some how disconcerting. On the other hand, initializing a new list, just to collect the items is a useless overhead ... What is the better design? How would it change, if DoSomethingWithStuff wouldn't be part of BaseItem but a third class? PS: there might be missing semicolons, or typos; sorry for that! The above code is not meant to be executed, but just for illustration.

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• Should I always encapsulate an internal data structure entirely?

  - by Prog

  Please consider this class: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThings(){ return things; } } This class exposes the array it uses to store data, to any client code interested. I did this in an app I'm working on. I had a ChordProgression class that stores a sequence of Chords (and does some other things). It had a Chord[] getChords() method that returned the array of chords. When the data structure had to change (from an array to an ArrayList), all client code broke. This made me think - maybe the following approach is better: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThing(int index){ return things[index]; } public int getDataSize(){ return things.length; } public void setThing(int index, Thing thing){ things[index] = thing; } } Instead of exposing the data structure itself, all of the operations offered by the data structure are now offered directly by the class enclosing it, using public methods that delegate to the data structure. When the data structure changes, only these methods have to change - but after they do, all client code still works. Note that collections more complex than arrays might require the enclosing class to implement even more than three methods just to access the internal data structure. Is this approach common? What do you think of this? What downsides does it have other? Is it reasonable to have the enclosing class implement at least three public methods just to delegate to the inner data structure?

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• Combinatorial explosion of interfaces: How many is too many?

  - by mga

  I'm a relative newcomer to OOP, and I'm having a bit of trouble creating good designs when it comes to interfaces. Consider a class A with N public methods. There are a number of other classes, B, C, ..., each of which interacts with A in a different way, that is, accesses some subset (<= N) of A's methods. The maximum degree of encapsulation is achieved by implementing an interface of A for each other class, i.e. AInterfaceForB, AInterfaceForC, etc. However, if B, C, ... etc. also interact with A and with each other, then there will be a combinatorial explosion of interfaces (a maximum of n(n-1), to be precise), and the benefit of encapsulation becomes outweighed by a code-bloat. What is the best practice in this scenario? Is the whole idea of restricting access to a class's public functions in different ways for other different classes just silly altogether? One could imagine a language that explicitly allows for this sort of encapsulation (e.g. instead of declaring a function public, one could specify exactly which classes it is visible to); Since this is not a feature of C++, maybe it's misguided to try to do it through the back door with interaces?

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• Architecture Question

  - by katie77

  I am writing a rules/eligibility Module. I have 2 sets of data, one is the customer data and the other is the customer products data. Customer data to Customer products data is one to many. Now I have to go through a set of Eligibility rules for each of this Customer product data. For each customer products data, I can say the customer is eligible for that product or decline the eligibility and should move on to the next product record. So in all the rules, I need to have access to customer and customer product data(the particular record that the rules are being executed against). Since all the rules can either approve a product or decline a product, I created an interface with those 2 methods and is implementing the this interface for all the rules. I am passing the Customer data and one product data for all the rules (because rules should be executed on each row of customer product data). An Ideal situation would be having the customer and customer product data available for the rule instead of passing them to each rule. What is the best way of doing this in-terms of architecture?

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• Using two ethernet connections (Internet enabled) simultaneously

  - by vedarthk

  I have searched and read over the Internet and also on askubuntu. i am using Ubuntu 11.04 and my question or the thing that I want to achieve is efficient use of both the connections and thus increasing my browsing and downloading speed. I want my system to decide which packet should be routed over which interface. I want to know if this is possible. For example, Is it possible to route alternate packets over the two interfaces ? Please let me know any Internet resource or If I would have to insert any code into the network drivers etc. ?

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• Override methods should call base method?

  - by Trevor Pilley

  I'm just running NDepend against some code that I have written and one of the warnings is Overrides of Method() should call base.Method(). The places this occurs are where I have a base class which has virtual properties and methods with default behaviour but which can be overridden by a class which inherits from the base class and doesn't call the overridden method. For example, in the base class I have a property defined like this: protected virtual char CloseQuote { get { return '"'; } } And then in an inheriting class which uses a different close quote: protected override char CloseQuote { get { return ']'; } } Not all classes which inherit from the base class use different quote characters hence my initial design. The alternatives I thought of were have get/set properties in the base class with the defaults set in the constructor: protected BaseClass() { this.CloseQuote = '"'; } protected char CloseQuote { get; set; } public InheritingClass() { this.CloseQuote = ']'; } Or make the base class require the values as constructor args: protected BaseClass(char closeQuote, ...) { this.CloseQuote = '"'; } protected char CloseQuote { get; private set; } public InheritingClass() base (closeQuote: ']', ...) { } Should I use virtual in a scenario where the base implementation may be replaced instead of extended or should I opt for one of the alternatives I thought of? If so, which would be preferable and why?

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• Should I create an Enum mapping to my database table

  - by CrazyHorse

  I have a database table containing a list of systems relevant to the tool I am building, mostly in-house applications, or third-party systems we receive data from. This table is added to infrequently, approx every 2 months. One of these systems is Windows itself, which is where we store our users' LANs, and I now need to explicitly reference the ID relating to Windows to query for user name, team etc. I know it would be bad practice to embed the ID itself into the code, so my question is what would be the best way to avoid this? I'm assuming my options are: create a global constant representing this ID create a global enum containing all systems now create a global enum and add systems to it as & when they are required in the code retrieve the ID from the database based on system name I appreciate this may seem a trivial question, but I am going to have many situations like this during the course of this build, and although we are in complete control of the database I would like to conform to best practice as far as possible. Many thanks!

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• Algorithm for optimal combination of two variables

  - by AlanChavez

  I'm looking for an algorithm that would be able to determine the optimal combination of two variables, but I'm not sure where to start looking. For example, if I have 10,000 rows in a database and each row contains price, and square feet is there any algorithm out there that will be able to determine what combination of price and sq ft is optimal. I know this is vague, but I assume is along the lines of Fuzzy logic and fuzzy sets, but I'm not sure and I'd like to start digging in the right field to see if I can come up with something that solves my problem.

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• Creating several instances of the same object, and selecting only one

  - by hustlerinc

  I'm playing around with making a puzzle game, haven't done that much before I run into my first problem. Basically, I want to create a certain amount of the same object/function. But without hardcoding the different instances. I think maybe an array is a good idea? and then a for loop to push the objects in? And then I need to be able to select one of these objects by clicking on it, how would I do that? How do I know which ball in the array was clicked? A loop again? I made a jsFiddle example (you need to click the orange ball to select, then you can move it around by clicking the canvas). This is what I want to do, but with more balls. How would you solve this? Help appreciated.

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• PHP I am pulling my hair out trying to find the best! [closed]

  - by darga33

  PULLING MY HAIR OUT I have heard of Martin Fowler's book PoEAA and the other book Head First OOA OOD but those are not in PHP. I DESPERATELY WANT TO READ THEM, but ONLY in PHP utilizing SOLID principles! Does anyone know of the absolute best, most recent PHP book that utilizes the SOLID principles and GRASP, and all the other best practices? I want to learn from the best possible source! Not beginner books! I already understand OOP. This seems like an almost impossible question to find the answer to and so I thought, hey, might as well post on stackexchange!! Surely someone out there must know!!!!!!!!!! Or if noone knows Maybe they know of an open source application that utilizes these principles that is relatively small that is not a framework. Something that I can go through every single class, and spend time understanding the insides and outs of how the program was developed. Thanks so much in advance! I really really really really appreciate it!

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• Two problems, both with either lock or suspend.

  - by user199208

  I recently did two things that may be the cause of either of them. 1) I started using a second screen 2) I installed xscreensaver instead of the stock, power saving option. My first question is about suspend: every time I wake from suspend, networking is disabled. While I've seen multiple posts about that on here, it didn't start happening until recently. Second, lock seems to be disabled now. Are both of these problems a bug, or was this caused by the second screen or maybe xscreensaver?

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• What is the 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 separate 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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• Sort rectangles in a grid based on a comparison of the center point of each

  - by Mrwolfy

  If I have a grid of rectangles and I move one of the rectangles, say above and to the left of another rectangle, how would I resort the rectangles? Note the rectangles are in an array, so each rectangle has an index and a matching tag. All I really need to do is set the proper index based on the rectangles new center point position within the rectangle, as compared with the center point position of the other rectangles in the grid. Here is what I am doing now in pseudo code (works somewhat, but not accurate): -(void)sortViews:myView { int newIndex; // myView is the view that was moved. [viewsArray removeObject:myView]; [viewsArray enumerate:obj*view]{ if (myView.center.x > view.center.x) { if (myView.center.y > view.center.y) { newIndex = view.tag -1; *stop = YES; } else { newIndex = view.tag +1; *stop = YES; } } else if (myView.center.x < view.center.x) { if (myView.center.y > view.center.y) { newIndex = view.tag -1; *stop = YES; } else { newIndex = view.tag +1; *stop = YES; } } }]; if (newIndex < 0) { newIndex = 0; } else if (newIndex > 5) { newIndex = 5; } [viewsArray insertObject:myView atIndex:newIndex]; [self arrangeGrid]; }

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• How to learn to deliver quality software designs when working on a tight deadline?

  - by chester89

  I read many books about how to design great software, but I kind of struggle to come up with a good design decisions when it comes to business apps, especially when the timeframe is tough. In the company I currently work for, the following situation happen all the time: my teamlead tells me that there's a task to do, I call some guy or a girl from business who tells me exactly what is it they want, and then I start coding. The task always fits in some existing application (we do only web apps or web services), usually it's purpose is to pull data from one datasource and put into the other one, with some business logic attached in the process. I start coding and then, after spending some time on a problem, my code didn't work as expected - either because of technical mistake or my lack of knowledge of the domain. The business is ringing me 2-3 times a day to hurry me up. I ask my team lead to help, he comes up, sees my code and goes like 'What's this?'. Then he throws away about half of my code, including all the design decisions I made, writes 2-3 methods that does the job (each of them usually 200-300 lines long or more, by the way), and task is complete, code works as it should have. The guy is smarter than me, obviously, and I'm aware of that. My goal is to be better software developer, that means write better code, not finish the job quicker with some crappy code. And the thing is, when I have enough time to tackle a problem, I can come up with a design that is good (in my opinion, of course), but I fall short to do so when I'm on a tight deadline. What should I do? I am fully aware that it's rather vague explanation, but please bear with me

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• Eleven Eleven Eleven Plus Two

  - by Larry Wake

  You probably already know that Oracle Solaris 11 11/11 was not in fact launched on 11/11/11.  We had our reasons, one of the primary ones being that would have collided with Veterans Day. But I'm going to venture a blog post today--even though it's again of course Veterans Day--to catch up on some news for Oracle Solaris 11's second anniversary (plus two days). Most recently, we had lots to talk about at Oracle OpenWorld -- Markus Flierl gives an excellent recap on his blog. Also, you can now download the various Solaris-related presentations that were given this year.  Find the list and links at: Focus on Oracle Solaris (http://bit.ly/OOW13-Solaris) If you follow the links above, you'll see there's lots to learn about how to get major benefits from Oracle Solaris 11 today, and you'll also find out about some of the new things we're busily at work on as well.  Onward to year three!

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