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• Advantages and disadvantages of building a single page web application

  - by ryanzec

  I'm nearing the end of a prototyping/proof of concept phase for a side project I'm working on, and trying to decide on some larger scale application design decisions. The app is a project management system tailored more towards the agile development process. One of the decisions I need to make is whether or not to go with a traditional multi-page application or a single page application. Currently my prototype is a traditional multi-page setup, however I have been looking at backbone.js to clean up and apply some structure to my Javascript (jQuery) code. It seems like while backbone.js can be used in multi-page applications, it shines more with single page applications. I am trying to come up with a list of advantages and disadvantages of using a single page application design approach. So far I have: Advantages All data has to be available via some sort of API - this is a big advantage for my use case as I want to have an API to my application anyway. Right now about 60-70% of my calls to get/update data are done through a REST API. Doing a single page application will allow me to better test my REST API since the application itself will use it. It also means that as the application grows, the API itself will grow since that is what the application uses; no need to maintain the API as an add-on to the application. More responsive application - since all data loaded after the initial page is kept to a minimum and transmitted in a compact format (like JSON), data requests should generally be faster, and the server will do slightly less processing. Disadvantages Duplication of code - for example, model code. I am going to have to create models both on the server side (PHP in this case) and the client side in Javascript. Business logic in Javascript - I can't give any concrete examples on why this would be bad but it just doesn't feel right to me having business logic in Javascript that anyone can read. Javascript memory leaks - since the page never reloads, Javascript memory leaks can happen, and I would not even know where to begin to debug them. There are also other things that are kind of double edged swords. For example, with single page applications, the data processed for each request can be a lot less since the application will be asking for the minimum data it needs for the particular request, however it also means that there could be a lot more small request to the server. I'm not sure if that is a good or bad thing. What are some of the advantages and disadvantages of single page web applications that I should keep in mind when deciding which way I should go for my project?

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• Is pixelmator a viable alternative for photoshop? [migrated]

  - by ChrisR

  I've always been a photoshop user, i know the ins and outs and know my way around all the tools i need for my webdesign work. But now i'm faced with a dilemma, for my new job i haven't got the budget for a full photoshop license so i'm wondering, is pixelmator a good alternative? I use Photoshop mainly to slice a design into separate images so enable/disable layers is a must, PSD compatibility too, ... Anyone has experience with Pixelmator?

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• What are the advantages of the delegate pattern over the observer pattern?

  - by JoJo

  In the delegate pattern, only one object can directly listen to another object's events. In the observer pattern, any number of objects can listen to a particular object's events. When designing a class that needs to notify other object(s) of events, why would you ever use the delegate pattern over the observer pattern? I see the observer pattern as more flexible. You may only have one observer now, but a future design may require multiple observers.

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• DDD and Value Objects. Are mutable Value Objects a good candidate for Non Aggr. Root Entity?

  - by Tony

  Here is a little problem Have an entity, with a value object. Not a problem. I replace a value object for a new one, then nhibernate inserts the new value and orphan the old one, then deletes it. Ok, that's a problem. Insured is my entity in my domain. He has a collection of Addresses (value objects). One of the addresses is the MailingAddress. When we want to update the mailing address, let's say zipcode was wrong, following Mr. Evans doctrine, we must replace the old object for a new one since it's immutable (a value object right?). But we don't want to delete the row thou, because that address's PK is a FK in a MailingHistory table. So, following Mr. Evans doctrine, we are pretty much screwed here. Unless i make my addressses Entities, so i don't have to "replace" it, and simply update its zipcode member, like the old good days. What would you suggest me in this case? The way i see it, ValueObjects are only useful when you want to encapsulate a group of database table's columns (component in nhibernate). Everything that has a persistence id in the database, is better off to make it an Entity (not necessarily an aggregate root) so you can update its members without recreating the whole object graph, specially if that's a deep-nested object. Do you concur? Is it allowed by Mr. Evans to have a mutable value object? Or is a mutable value object a candidate for an Entity? Thanks

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• How did you get good practices for your OOP designs?

  - by Darf Zon

  I realized I have a difficulty creating OOP designs. I spent many time deciding if this property is correctly set it to X class. For example, this is a post which has a few days: http://codereview.stackexchange.com/questions/8041/how-to-improve-my-factory-design I'm not convinced of my code. So I want to improve my designs, take less time creating it. How did you learn creating good designs? Some books that you can recommend me?

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• Algorithm for dynamically calculating a level based on experience points?

  - by George

  One of the struggles I've always had in game development is deciding how to implement experience points attributed to gaining a level. There doesn't seem to be a pattern to gaining a level in many of the games I've played, so I assume they have a static dictionary table which contains experience points vs. the level. e.g. Experience Level 0 1 100 2 175 3 280 4 800 5 ...There isn't a rhyme or reason why 280 points is equal to level 4, it just is. I'm not sure how those levels are decided, but it certainly wouldn't be dynamic. I've also thought about the possibility of exponential levels, as not to have to keep a separate lookup table, e.g. Experience Level 0 1 100 2 200 3 400 4 800 5 1600 6 3200 7 6400 8 ...but that seems like it would grow out of control rather quickly, as towards the upper levels, the enemies in the game would have to provide a whopping amount of experience to level -- and that would be to difficult to control. Leveling would become an impossible task. Does anyone have any pointers, or methods they use to decide how to level a character based on experience? I want to be fair in leveling and I want to stay ahead of the players as not to worry about constantly adding new experience/level lookups.

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• Single Responsibility Principle Implementation

  - by Mike S

  In my spare time, I've been designing a CMS in order to learn more about actual software design and architecture, etc. Going through the SOLID principles, I already notice that ideas like "MVC", "DRY", and "KISS", pretty much fall right into place. That said, I'm still having problems deciding if one of two implementations is the best choice when it comes to the Single Responsibility Principle. Implementation #1: class User getName getPassword getEmail // etc... class UserManager create read update delete class Session start stop class Login main class Logout main class Register main The idea behind this implementation is that all user-based actions are separated out into different classes (creating a possible case of the aptly-named Ravioli Code), but following the SRP to a "tee", almost literally. But then I thought that it was a bit much, and came up with this next implementation class UserView extends View getLogin //Returns the html for the login screen getShortLogin //Returns the html for an inline login bar getLogout //Returns the html for a logout button getRegister //Returns the html for a register page // etc... as needed class UserModel extends DataModel implements IDataModel // Implements no new methods yet, outside of the interface methods // Haven't figured out anything special to go here at the moment // All CRUD operations are handled by DataModel // through methods implemented by the interface class UserControl extends Control implements IControl login logout register startSession stopSession class User extends DataObject getName getPassword getEmail // etc... This is obviously still very organized, and still very "single responsibility". The User class is a data object that I can manipulate data on and then pass to the UserModel to save it to the database. All the user data rendering (what the user will see) is handled by UserView and it's methods, and all the user actions are in one space in UserControl (plus some automated stuff required by the CMS to keep a user logged in or to ensure that they stay out.) I personally can't think of anything wrong with this implementation either. In my personal feelings I feel that both are effectively correct, but I can't decide which one would be easier to maintain and extend as life goes on (despite leaning towards Implementation #1.) So what about you guys? What are your opinions on this? Which one is better? What basics (or otherwise, nuances) of that principle have I missed in either design?

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• Started wrong with a project. Should I start over?

  - by solidsnake

  I'm a beginner web developer (one year of experience). A couple of weeks after graduating, I got offered a job to build a web application for a company whose owner is not much of a tech guy. He recruited me to avoid theft of his idea, the high cost of development charged by a service company, and to have someone young he can trust onboard to maintain the project for the long run (I came to these conclusions by myself long after being hired). Cocky as I was back then, with a diploma in computer science, I accepted the offer thinking I can build anything. I was calling the shots. After some research I settled on PHP, and started with plain PHP, no objects, just ugly procedural code. Two months later, everything was getting messy, and it was hard to make any progress. The web application is huge. So I decided to check out an MVC framework that would make my life easier. That's where I stumbled upon the cool kid in the PHP community: Laravel. I loved it, it was easy to learn, and I started coding right away. My code looked cleaner, more organized. It looked very good. But again the web application was huge. The company was pressuring me to deliver the first version, which they wanted to deploy, obviously, and start seeking customers. Because Laravel was fun to work with, it made me remember why I chose this industry in the first place - something I forgot while stuck in the shitty education system. So I started working on small projects at night, reading about methodologies and best practice. I revisited OOP, moved on to object-oriented design and analysis, and read Uncle Bob's book Clean Code. This helped me realize that I really knew nothing. I did not know how to build software THE RIGHT WAY. But at this point it was too late, and now I'm almost done. My code is not clean at all, just spaghetti code, a real pain to fix a bug, all the logic is in the controllers, and there is little object oriented design. I'm having this persistent thought that I have to rewrite the whole project. However, I can't do it... They keep asking when is it going to be all done. I can not imagine this code deployed on a server. Plus I still know nothing about code efficiency and the web application's performance. On one hand, the company is waiting for the product and can not wait anymore. On the other hand I can't see myself going any further with the actual code. I could finish up, wrap it up and deploy, but god only knows what might happen when people start using it. What do you think I should do?

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• How can I solve the same problems a CB-architecture is trying to solve without using hacks? [on hold]

  - by Jefffrey

  A component based system's goal is to solve the problems that derives from inheritance: for example the fact that some parts of the code (that are called components) are reused by very different classes that, hypothetically, would lie in a very different branch of the inheritance tree. That's a very nice concept, but I've found out that CBS is often hard to accomplish without using ugly hacks. Implementations of this system are often far from clean. But I don't want to discuss this any further. My question is: how can I solve the same problems a CBS try to solve with a very clean interface? (possibly with examples, there are a lot of abstract talks about the "perfect" design already). Here's an example I was going for before realizing I was just reinventing inheritance again: class Human { public: Position position; Movement movement; Sprite sprite; // other human specific components }; class Zombie { Position position; Movement movement; Sprite sprite; // other zombie specific components }; After writing that I realized I needed an interface, otherwise I would have needed N containers for N different types of objects (or to use boost::variant to gather them all together). So I've thought of polymorphism (move what systems do in a CBS design into class specific functions): class Entity { public: virtual void on_event(Event) {} // not pure virtual on purpose virtual void on_update(World) {} virtual void on_draw(Window) {} }; class Human { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; class Zombie { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; Which was nice, except for the fact that now the outside world would not even be able to know where a Human is positioned (it does not have access to its position member). That would be useful to track the player position for collision detection or if on_update the Zombie would want to track down its nearest human to move towards him. So I added const Position& get_position() const; to both the Zombie and Human classes. And then I realized that both functionality were shared, so it should have gone to the common base class: Entity. Do you notice anything? Yes, with that methodology I would have a god Entity class full of common functionality (which is the thing I was trying to avoid in the first place).

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• Designing Videogame Character Parodies [duplicate]

  - by David Dimalanta

  This question already has an answer here: Is it legal to add a cameo appearance of a known video game character in my game? 2 answers Was it okay to make a playable character when making a videogame despite its resemblance? For example, I'm making a 3rd-person action-platform genre and I have to make a character design resembling like Megaman but not exactly the same as him since there is little alternate in color, details, and facial features.

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• What's the problem with Scala's XML literals?

  - by Oak

  In this post, Martin (the language's head honcho) writes: [XML literals] Seemed a great idea at the time, now it sticks out like a sore thumb. I believe with the new string interpolation scheme we will be able to put all of XML processing in the libraries, which should be a big win. Being interested in language design myself, I'm wondering: Why does he write that it was a mistake to incorporate XML literals into the language? What is the controversy regarding this feature?

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• SQL: empty string vs NULL value

  - by Jacek Prucia

  I know this subject is a bit controversial and there are a lot of various articles/opinions floating around the internet. Unfortunatelly, most of them assume the person doesn't know what the difference between NULL and empty string is. So they tell stories about surprising results with joins/aggregates and generally do a bit more advanced SQL lessons. By doing this, they absolutely miss the whole point and are therefore useless for me. So hopefully this question and all answers will move subject a bit forward. Let's suppose I have a table with personal information (name, birth, etc) where one of the columns is an email address with varchar type. We assume that for some reason some people might not want to provide an email address. When inserting such data (without email) into the table, there are two available choices: set cell to NULL or set it to empty string (''). Let's assume that I'm aware of all the technical implications of choosing one solution over another and I can create correct SQL queries for either scenario. The problem is even when both values differ on the technical level, they are exactly the same on logical level. After looking at NULL and '' I came to a single conclusion: I don't know email address of the guy. Also no matter how hard i tried, I was not able to sent an e-mail using either NULL or empty string, so apparently most SMTP servers out there agree with my logic. So i tend to use NULL where i don't know the value and consider empty string a bad thing. After some intense discussions with colleagues i came with two questions: am I right in assuming that using empty string for an unknown value is causing a database to "lie" about the facts? To be more precise: using SQL's idea of what is value and what is not, I might come to conclusion: we have e-mail address, just by finding out it is not null. But then later on, when trying to send e-mail I'll come to contradictory conclusion: no, we don't have e-mail address, that @!#$ Database must have been lying! Is there any logical scenario in which an empty string '' could be such a good carrier of important information (besides value and no value), which would be troublesome/inefficient to store by any other way (like additional column). I've seen many posts claiming that sometimes it's good to use empty string along with real values and NULLs, but so far haven't seen a scenario that would be logical (in terms of SQL/DB design). P.S. Some people will be tempted to answer, that it is just a matter of personal taste. I don't agree. To me it is a design decision with important consequences. So i'd like to see answers where opion about this is backed by some logical and/or technical reasons.

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• What's the most useful 10% of UML and is there a quick tutorial on it?

  - by Hanno Fietz

  I want my scribbles of a program's design and behaviour to become more streamlined and have a common language with other developers. I looked at UML and in principle it seems to be what I'm looking for, just way overkill. The information I found online also seems very bloated and academic. Is there a no-bullshit, 15-minutes introduction to the handful of UML symbols I'll need when discussing the architecture of some garden variety software on a whiteboard with my colleagues?

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• "UML is the worst thing to ever happen to MDD." Why?

  - by Florents

  William Cook in a tweet wrote that: "UML is the worst thing to ever happen to MDD. Fortunately many people now realize this ..." I would like to know the reasoning behind that claim (apparently, I'm not referring to his personal opinion). I've noticed that many people out there don't like UML that much. Also it is worth mentioning that he is in academia, where UML is preety much the holy grail of effective design and modelling.

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• As a tooling/automation developer, can I be making better use of OOP?

  - by Tom Pickles

  My time as a developer (~8 yrs) has been spent creating tooling/automation of one sort or another. The tools I develop usually interface with one or more API's. These API's could be win32, WMI, VMWare, a help-desk application, LDAP, you get the picture. The apps I develop could be just to pull back data and store/report. It could be to provision groups of VM's to create live like mock environments, update a trouble ticket etc. I've been developing in .Net and I'm currently reading into design patterns and trying to think about how I can improve my skills to make better use of and increase my understanding of OOP. For example, I've never used an interface of my own making in anger (which is probably not a good thing), because I honestly cannot identify where using one would benefit later on when modifying my code. My classes are usually very specific and I don't create similar classes with similar properties/methods which could use a common interface (like perhaps a car dealership or shop application might). I generally use an n-tier approach to my apps, having a presentation layer, a business logic/manager layer which interfaces with layer(s) that make calls to the API's I'm working with. My business entities are always just method-less container objects, which I populate with data and pass back and forth between my API interfacing layer using static methods to proxy/validate between the front and the back end. My code by nature of my work, has few common components, at least from what I can see. So I'm struggling to see how I can better make use of OOP design and perhaps reusable patterns. Am I right to be concerned that I could be being smarter about how I work, or is what I'm doing now right for my line of work? Or, am I missing something fundamental in OOP? EDIT: Here is some basic code to show how my mgr and api facing layers work. I use static classes as they do not persist any data, only facilitate moving it between layers. public static class MgrClass { public static bool PowerOnVM(string VMName) { // Perform logic to validate or apply biz logic // call APIClass to do the work return APIClass.PowerOnVM(VMName); } } public static class APIClass { public static bool PowerOnVM(string VMName) { // Calls to 3rd party API to power on a virtual machine // returns true or false if was successful for example } }

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• Go/Obj-C style interfaces with ability to extend compiled objects after initial release

  - by Skrylar

  I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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• Should I use JavaFx properties?

  - by Mike G

  I'm usually very careful to keep my Model, View, and Controller code separate. The thing is JavaFx properties are so convenient to bind them all together. The issue is that it makes my entire code design dependent on JavaFx, which I feel I should not being doing. I should be able to change the view without changing too much of the model and controller. So should I ignore the convenience of JavaFx properties, or should I embrace them and the fact that it reduces my codes flexibility.

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• What are DRY, KISS, SOLID, etc. classified as?

  - by Morgan Herlocker

  Is something like DRY a design pattern, a methodology, or something in between? They do not have specific implementations that could neccessarily be demonstrated(even if you can easily demonstrate a case NOT using something like KISS... see The Daily WTF for a plethora of examples), nor do they fully explain a development process like a methodology generally would. Where does that leave these types of "rule of thumb"'s?

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• What are the essential things one needs to know about UML?

  - by Hanno Fietz

  I want my scribbles of a program's design and behaviour to become more streamlined and have a common language with other developers. I looked at UML and in principle it seems to be what I'm looking for, but it seems to be overkill. The information I found online also seems very bloated and academic. How can I understand UML in plain-English way, enough to be able to explain it to my colleagues? What are the canonical resources for understanding UML at a ground level?

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• Starting all over again?

  - by kyndigs

  Have you ever been developing something and just came to a point where you think that this is rubbish, the design is bad and although I will lose time it will be better to just start all over again? What should you consider before making this step? I know it can be drastic in some cases, is it best to just totally ignore what you did before, or take some of the best bits from it? Some real life examples would be great.

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• How should I structure my database to gain maximum efficiently in this scenario?

  - by Bob Jansen

  I'm developing a PHP script that analyzes the web traffic of my clients websites. By placing a link to a javascript on the clients website (think of Google Analyses), my script harvests information like: the visitors IP address, reference link, current page link, user agent, etc. Now my clients can view these statistics via a control panel that I have build. These clients can also adjust profile settings, set firewall rules, create support tickets and pay invoices. Currently all the the traffic is stored in one table. You can imagine that this tabel would become very large as some my clients receive thousands of pageviews per day. Furthermore, all the traffic data of each client would be stored in the same table, creating a mess. This is the same for the firewall rules currently, and the invoice and support system. I'm looking for way to structure my database in a more organized way to hold large amounts of data of multiple users. This is the first project that I'm developing that deals with so much data, and would like to hear suggestions and tips. I was thinking of using multiple databases to structure the data. The main database will store users data (email,pass,id,etc) admin/website settings. Than each client will have an unique database labeled prefix_userid, which carry tables holding their traffic, invoice, and support ticket data. Would this be a solution, and would it slow down or speed up overall performances (that is spreading the data over muliple databases). I have a solid VPS, but would like to safe and be as effient as possible.

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• Nested Entities and calculation on leaf entity property - SQL or NoSQL approach

  - by Chandu

  I am working on a hobby project called Menu/Recipe Management. This is how my entities and their relations look like. A Nutrient has properties Code and Value An Ingredient has a collection of Nutrients A Recipe has a Collection of Ingredients and occasionally can have a collection of other recipes A Meal has a Collection of Recipes and Ingredients A Menu has a Collection of Meals The relations can be depicted as In one of the pages, for a selected menu I need to display the effective nutrients information calculated based on its constituents (Meals, Recipes, Ingredients and the corresponding nutrients). As of now am using SQL Server to store the data and I am navigating the chain from my C# code, starting from each meal of the menu and then aggregating the nutrient values. I think this is not an efficient way as this calculation is being done every time the page is requested and the constituents change occasionally. I was thinking about a having a background service that maintains a table called MenuNutrients ({MenuId, NutrientId, Value}) and will populate/update this table with the effective nutrients when any of the component (Meal, Recipe, Ingredient) changes. I feel that a GraphDB would be a good fit for this requirement, but my exposure to NoSQL is limited. I want to know what are the alternative solutions/approaches to this requirement of displaying the nutrients of a given menu. Hope my description of the scenario is clear.

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• How to store prices that have effective dates?

  - by lal00

  I have a list of products. Each of them is offered by N providers. Each providers quotes us a price for a specific date. That price is effective until that provider decides to set a new price. In that case, the provider will give the new price with a new date. The MySQL table header currently looks like: provider_id, product_id, price, date_price_effective Every other day, we compile a list of products/prices that are effective for the current day. For each product, the list contains a sorted list of the providers that have that particular product. In that way, we can order certain products from whoever happens to offer the best price. To get the effective prices, I have a SQL statement that returns all rows that have date_price_effective >= NOW(). That result set is processed with a ruby script that does the sorting and filtering necessary to obtain a file that looks like this: product_id_1,provider_1,provider_3,provider8,provider_10... product_id_2,provider_3,provider_2,provider1,provider_10... This works fine for our purposes, but I still have an itch that a SQL table is probably not the best way to store this kind of information. I have that feeling that this kind of problema has been solved previously in other more creative ways. Is there a better way to store this information other than in SQL? or, if using SQL, is there a better approach than the one I'm using?

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• Should I use multiple column primary keys or add a new colum?

  - by Covar

  My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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• I need an approach to the problem of preventing inserting duplicate records into the database

  - by Maurice

  Apologies is this question is asked on the incorrect "stack" A webservice that I call returns a list of data. The data from the webservice is updated periodically, so a call to the webservice done in one hour could return the same data as a call done in an hour. Also, the data is returned based on a start and end date. We have multiple users that can run the webservice search, and duplicate data is most likely to be returned (especially for historical data). However I don't want to insert this duplicate data in the database. I've created a db table in which the data is stored (most important columns are) Id int autoincrement PK Date date not null --The date to which the data set belongs. LastUpdate date not null --The date the data set was last updated. UserName varchar(50) --The name of the user doing the search. I use sql server 2008 express with c# 4.0 and visual studio 2010. Entity Framework is used as the ORM. If stored procedures could be avoided in the proposed solution, then that will be a plus. Another way of looking interpreting what I'm asking a solution for is as follows: I have a million unique records in my table. A user does a new search. The search results from the user contains around 300k of the data that is already in the db. An efficient solution to finding an inserting only the unique records is needed.

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