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  • How to develop Online Shopping Portal Application using PHP ?

    - by Sarang
    I do not know PHP & I have to develop a Shopping Portal with following Definition : Scenario: Online Shopping Portal XYZ.com wants to create an online shopping portal for managing its registered customers and their shopping. The customers need to register themselves first before they do shopping using the shopping portal. However, everyone, whether registered or not, can view the various products along with the prices listed in the portal. The registered customers, after logging in, are allowed to place order for one or more products from the products listed in the portal. Once the order is placed, the customer gets a reference order number and the order status should be “order in process”. The customers can track their order using the given reference number. The management of XYZ.com should be able to modify the order status of a particular reference order number to “shipped” once the products are shipped to the shipping address entered by the customer at the time of placing the order. The Functionalities required are : Create the interface for the XYZ.com shopping portal using HTML/XHTML and CSS. Implement the client side validations using JavaScript. Create the tables using MySQL. Implement the functionality using the server side scripting language, PHP. Integrate all the above tasks and make the XYZ.com shopping portal functional. How do I develop this application with following proper steps of development ?

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  • Inventory Management concepts in XNA game

    - by user1332755
    I am trying to code the inventory system in my first real game so I have very little experience in both c# and game engine development. Basically, I need some general guidance and tips with how to structure and organize these sorts of systems. Please tell me if I am on the right track or not before I get too deep into making some badly structured system. It's fine if you don't feel like looking through my code, suggestions about general structure would also be appreciated. What I am aiming to end up with is some sort of system like Minecraft or Terraria. It must include: main inventory GUI (items can be dragged and placed in whatever slot desired Itembar outside of the main inventory which can be assigned to certain items the ability to use items from either location So far, I have 4 main classes: Inventory holds the general info and methods, inventoryslot holds info for individual slots, Itembar holds all info and methods for itself, and finally, ItemManager to manage interactions between the two and hold a master list of items. So far, my itembar works perfectly and interacts well with mousedragging items into and out of it as well as activating the item effect. Here is the code I have so far: (there is a lot but I will try to keep it relevant) This is the code for the itembar on the main screen: class Itembar { public Texture2D itembarfull, iSelected; public static Rectangle itembar = new Rectangle(5, 218, 40, 391); public Rectangle box1 = new Rectangle(itembar.X, 218, 40, 40); //up to 10 Rectangles for each slot public int Selected = 0; private ItemManager manager; public Itembar(Texture2D texture, Texture2D texture3, ItemManager mann) { itembarfull = texture; iSelected = texture3; manager = mann; } public void Update(GameTime gametime) { } public void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw( itembarfull, new Vector2 (itembar.X, itembar.Y), null, Color.White, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 1.0f); if (Selected == 1) spriteBatch.Draw(iSelected, new Rectangle(box1.X-3, box1.Y-3, box1.Width+6, box1.Height+6), Color.White); //goes up to 10 slots } public int Box1Query() { foreach (Item item in manager.items) { if(box1.Contains(item.BoundingBox)) return manager.items.IndexOf(item); } return 999; } //10 different box queries It is working fine right now. I just put an Item in there and the box will query things like the item's effects, stack number, consumable or not etc...This one is basically almost complete. Here is the main inventory class: class Inventory { public bool isActive; public List<Rectangle> mainSlots = new List<Rectangle>(24); public List<InventorySlot> mainSlotscheck = new List<InventorySlot>(24); public static Rectangle inv = new Rectangle(841, 469, 156, 231); public Rectangle invfull = new Rectangle(inv.X, inv.Y, inv.Width, inv.Height); public Rectangle inv1 = new Rectangle(inv.X + 4, inv.Y +3, 32, 32); //goes up to inv24 resulting in a 6x4 grid of Rectangles public Inventory() { mainSlots.Add(inv1); mainSlots.Add(inv2); mainSlots.Add(inv3); mainSlots.Add(inv4); //goes up to 24 foreach (Rectangle slot in mainSlots) mainSlotscheck.Add(new InventorySlot(slot)); } //update and draw methods are empty because im not too sure what to put there public int LookforfreeSlot() { int slotnumber = 999; for (int x = 0; x < mainSlots.Count; x++) { if (mainSlotscheck[x].isFree) { slotnumber = x; break; } } return slotnumber; } } } LookforFreeSlot() method is meant to be called when I do AddtoInventory(). I'm kinda stumped about what other things I need to put in this class. Here is the inventorySlot class: (its main purpose is to check the bool "isFree" to see whether or not something already occupies the slot. But i guess it can also do other stuff like get item info.) class InventorySlot { public int X, Y; public int Width = 32, Height = 32; public Vector2 Position; public int slotnumber; public bool free = true; public int? content = null; public bool isFree { get { return free; } set { free = value; } } public InventorySlot(Rectangle slot) { slot = new Rectangle(X, Y, Width, Height); } } } Finally, here is the ItemManager (I am omitting the master list because it is too long) class ItemManager { public List<Item> items = new List<Item>(20); public List<Item> inventory1 = new List<Item>(24); public List<Item> inventory2 = new List<Item>(24); public List<Item> inventory3 = new List<Item>(24); public List<Item> inventory4 = new List<Item>(24); public Texture2D icon, filta; private Rectangle msRect; MouseState mouseState; public int ISelectedIndex; Inventory inventory; SpriteFont font; public void GenerateItems() { items.Add(new Item(new Rectangle(0, 0, 32, 32), icon, font)); items[0].name = "Grass Chip"; items[0].itemID = 0; items[0].consumable = true; items[0].stackable = true; items[0].maxStack = 99; items.Add(new Item(new Rectangle(32, 0, 32, 32), icon, font)); //master list continues. it will generate all items in the game; } public ItemManager(Inventory inv, Texture2D itemsheet, Rectangle mouseRectt, MouseState ms, Texture2D fil, SpriteFont f) { icon = itemsheet; msRect = mouseRectt; filta = fil; mouseState = ms; inventory = inv; font = f; } //once again, no update or draw public void mousedrag() { items[0].DestinationRect = new Rectangle (msRect.X, msRect.Y, 32, 32); items[0].dragging = true; } public void AddtoInventory(Item item) { int index = inventory.LookforfreeSlot(); if (index == 999) return; item.DestinationRect = inventory.mainSlots[index]; inventory.mainSlotscheck[index].content = item.itemID; inventory.mainSlotscheck[index].isFree = false; item.IsActive = true; } } } The mousedrag works pretty well. AddtoInventory doesn't work because LookforfreeSlot doesn't work. Relevant code from the main program: When I want to add something to the main inventory, I do something like this: foreach (Particle ether in ether1.ethers) { if (ether.isCollected) itemmanager.AddtoInventory(itemmanager.items[14]); } This turned out to be much longer than I had expected :( But I hope someone is interested enough to comment.

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  • Notifying a separate application of an event

    - by TomDestry
    I have an application that runs through various tasks as an automated process. My client would like me to create a file in a given folder for each task as a way to flag when each task completes. They prefer this to a database flag because they can be notified by the file system rather than continually polling a database table. I can do this but creating and deleting files as flags feels clunky. Is there a more elegant approach to notifying a third-party of an event?

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  • Move Background in AndEngine for a Racing Game

    - by Nathiya
    I am new to game development and AndEngine. I have small query about racing game. I am going to develop a bike racing game. For bike racing game we will move the background or the player. I am tried with andengine autoparallax background. But I didn't got the correct answer. I need to do a background like these screenshots in SpeedMoto. Can anyone help me to set the background.

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  • Styles of games that work at low-resolution

    - by Brendan Long
    I'm taking a class on compilers, and the goal is to write a compiler for Meggy Jr devices (Arduino). The goal is just to make a simple compilers with loops and variables and stuff. Obviously, that's lame, so the "real goal" is to make an impressive game on the device. The problem is that it only has 64 pixels to work with (technically 72, but the top 8 are single-color and not part of the main display, so they're really only useful for displaying things like money). My problem is thinking of something to do on a device that small. It doesn't really matter if it's original, but it can't be something that's already available. My first idea was "snake", but that comes with the SDK. Same with a side-scrolling shooter. Remaining ideas include a tower defense game (hard to write, hard to control), an RPG (same), tetris (lame).. The problem is that all of the games I like require a high-resolution screen because they have a lot of text. Even a really simple game like nethack would be hard because each creature would be a single color. tl;dr What styles of games require a. No text; and b. Few enough objects that representing them each with a single color is acceptable? EDIT: To clarify, the display is 8x8 for a total of 64 pixels, not 64x64.

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  • What are some good examples of exuberant in-game instructions for telling the player to repeatedly smash a button?

    - by Michael
    What are some good examples of exuberant in-game instructions for telling the player to repeatedly and quickly press a button or perform an action? I'm especially interested in examples in retro games (e.g., from the NES, SNES, and 1980-90s arcade eras), and I would love to see examples with text, graphics, or both. To illustrate, here are a few examples of the type of instructions that I'm thinking of: Smash the A button to lift something heavy! Toggle the joystick back and forth to break free! Quickly press the button to build power in a meter! I'm working on a 2D iOS game with retro-style pixel art, and there's a point where I want the player to quickly tap on a sprite to complete an action. I have a serviceable starting point -- the word "TAP" flashing with an arrow repeatedly moving downward beneath it: But it still doesn't feel quite right. I would love to see some actual examples from the golden days of 2D gaming to use as reference material. I know examples abound, but I'm just struggling to think of any concrete ones at the moment. Can you think of any examples of this type of thing in old games?

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  • Help in (re)designing my Swing application

    - by Harihar Das
    I have developed a Swing application that controls execution of several script like jobs. I need to display the interim output of the jobs concurrently. I have followed MVC while writing the application. The application is working as expected. But off late I have the following requirements in hand: A few of the script jobs need special user privileges to execute so as to access specialized resources. There seems to be now way in Java to impersonate as a different user while running an application.[examined in this question]. Also trying to run the Swing application as a scheduled task in windows is not helping. Once started the jobs should be running even if the user logs off after starting the jobs. I am thinking of separating the execution logic from the UI and run that as a service; and introduce JMS in between the two layers so as to store/retrieve the interim the output. Note: I need to run this application on windows Any ideas on meeting my requirements will be highly appreciated.

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  • responsibility for storage

    - by Stefano Borini
    A colleague and I were brainstorming about where to put the responsibility of an object to store itself on the disk in our own file format. There are basically two choices: object.store(file) fileformatWriter.store(object) The first one gives the responsibility of serialization on the disk to the object itself. This is similar to the approach used by python pickle. The second groups the representation responsibility on a file format writer object. The data object is just a plain data container (eventually with additional methods not relevant for storage). We agreed on the second methodology, because it centralizes the writing logic from generic data. We also have cases of objects implementing complex logic that need to store info while the logic is in progress. For these cases, the fileformatwriter object can be passed and used as a delegate, calling storage operations on it. With the first pattern, the complex logic object would instead accept the raw file, and implement the writing logic itself. The first method, however, has the advantage that the object knows how to write and read itself from any file containing it, which may also be convenient. I would like to hear your opinion before starting a rather complex refactoring.

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  • Architecture/pattern resources for small applications and tools

    - by s73v3r
    I was wondering if anyone had any resources or advice related to using architecture patterns like MVVM/MVC/MVP/etc on small applications and tools, as opposed to large, enterprisy ones. EDIT: Most of the information I see on application architecture is directed at large, enterprise applications. I'm just writing small programs and tools. As far as using these architecture patterns, is it generally worthwhile to go through the overhead of using an MVC/MVVM framework? Or would I be better off keeping it simple?

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  • Styles of games that work at low-resolution

    - by Brendan Long
    I'm taking a class on compilers, and the goal is to write a compiler for Meggy Jr devices (Arduino). The goal is just to make a simple compilers with loops and variables and stuff. Obviously, that's lame, so the "real goal" is to make an impressive game on the device. The problem is that it only has 64 pixels to work with (technically 72, but the top 8 are single-color and not part of the main display, so they're really only useful for displaying things like money). My problem is thinking of something to do on a device that small. It doesn't really matter if it's original, but it can't be something that's already available. My first idea was "snake", but that comes with the SDK. Same with a side-scrolling shooter. Remaining ideas include a tower defense game (hard to write, hard to control), an RPG (same), tetris (lame).. The problem is that all of the games I like require a high-resolution screen because they have a lot of text. Even a really simple game like nethack would be hard because each creature would be a single color. tl;dr What styles of games require a. No text; and b. Few enough objects that representing them each with a single color is acceptable?

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  • Website restyle, SEO migration plan?

    - by Goboozo
    I am currently in a project for one of my biggest clients. We have built a website that will -replace- the old website. When it comes to actual content its is largely the same. However, the presentation of the content has changed drastically. From our point of view much more user-friendly (main reason to update the site). Now, since the sites presentation has changed we have some major changes in: HTML & CSS: To change the presentation of the content URL's: To make them better understandable (301 redirects have been taken care of and are in place) Breadcrumbs: To enhance the navigation (we have made the breadcrumbs match exactly with the url's) Pagination: This was added to enable content browsing Title tags: Added descriptive title tags to the major links and buttons. Basically all user content including meta tags have remained the same. Now since this company is rather successful and 90% of its clients come from Google's organic results I am obliged to take all necessary precautions. People tell me I need a migration plan to prevent the site being hurt in Google, but I have never worked using such a plan... ...So, based on the above. Would you consider a migration plan necessary and what precautions/actions would you recommend to prevent us being put down in our SERP positions? Many thanks in advance for your answers.

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  • Should programmers prefer making wide libraries or thin libraries?

    - by Telastyn
    For classes and functions, it is clear cut: each should do only one thing. For libraries though, this is less clear. If you have a library with collections, it might have multiple collections. It might have useful functions like sorting, which aren't strictly collection based but users would expect. Each of these results in a 'wider' library. On the other side is having a library for the specific collection type and/or with little built-in functionality. If you want a queue, it gives you a queue. If you want to sort that list, then the library lets you do that yourself. What is the best practice here (if any)? I can see arguments for each side.

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  • How can I separate the user interface from the business logic while still maintaining efficiency?

    - by Uri
    Let's say that I want to show a form that represents 10 different objects on a combobox. For example, I want the user to pick one hamburguer from 10 different ones that contain tomatoes. Since I want to separate UI and logic, I'd have to pass the form a string representation of the hamburguers in order to display them on the combobox. Otherwise, the UI would have to dig into the objects fields. Then the user would pick a hamburguer from the combobox, and submit it back to the controller. Now the controller would have to find again said hamburguer based on the string representation used by the form (maybe an ID?). Isn't that incredibly inefficient? You already had the objects you wanted to pick one from. If you submited to the form the whole objects, and then returned a specific object, you wouldn't have to refind it later on since the form already returned a reference to that object. Moreover, if I'm wrong and you actually should send the whole object to the form, how can I isolate UI from logic?

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  • How do multi-platform games usually store save data?

    - by PixelPerfect3
    I realize this is a bit of a broad question, but I was wondering if there is a "standard" in the industry when it comes to storing save data for games (and is it different across platforms - Xbox/PS/PC/Mac/Android/iOS?) For example for a game like Assassin's Creed or The Walking Dead: They are on multiple platforms and they usually have to save enough information about the player and their actions. Do they use something like XML files, databases, or just straight binary dumps? How much does it differ from platform to platform? I would appreciate it if someone with experience in the game industry would answer this.

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  • What would a database look like if it were normalized to be completely abstracted? lets call it Max(n) normal form

    - by Doug Chamberlain
    edit: By simplest form i was not implying that it would be easy to understand. For instance, developing in low level assembly language is the simplest way to can develop code, but it is far from the easiest. Essentially, what I am asking is in math you can simplify a fraction to a point where it can no longer be simplfied. Can the same be true for a database and what would a database look like in its simplest, form?

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  • How can I make an MMORPG appeal to casual players?

    - by Philipp
    I believe that there is a significant market of players who would enjoy the exploration and interaction aspects of MMORPGs, but simply don't have the time for the endless grinding marathons which are part of the average MMORPG. MMORPGs are all about interaction between players. But when different players have different amounts of time to invest into a game, those with less time to spend will soon lack behind their power-leveling friends and won't be able to interact with them anymore. One way to solve this would be to limit the progress a player can achieve per day, so that it simply doesn't make sense to play more than one or two hours a day. But even the busiest casual players sometimes like to spend a whole sunday afternoon playing a video game. Just stopping them after two hours would be really frustrating. It also creates a pressure to use the daily progress limit every day, because otherwise the player would feel like wasting something. This pressure would be detrimental for casual gamers. What else could be done to level the playing field between those players who play 40+ hours a week and those who can't play more than 10?

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  • When do you use a struct instead of a class?

    - by jkohlhepp
    What are your rules of thumb for when to use structs vs. classes? I'm thinking of the C# definition of those terms but if your language has similar concepts I'd like to hear your opinion as well. I tend to use classes for almost everything, and use structs only when something is very simplistic and should be a value type, such as a PhoneNumber or something like that. But this seems like a relatively minor use and I hope there are more interesting use cases.

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  • How to avoid big and clumsy UITableViewController on iOS?

    - by Johan Karlsson
    I have a problem when implementing the MVC-pattern on iOS. I have searched the Internet but seems not to find any nice solution to this problem. Many UITableViewController implementations seems to be rather big. Most examples I have seen lets the UITableViewController implement <UITableViewDelegate> and <UITableViewDataSource>. These implementations are a big reason why UITableViewControlleris getting big. One solution would be to create separate classes that implements <UITableViewDelegate> and <UITableViewDataSource>. Of course these classes would have to have a reference to the UITableViewController. Are there any drawbacks using this solution? In general I think you should delegate the functionality to other "Helper" classes or similar, using the delegate pattern. Are there any well established ways of solving this problem? I do not want the model to contain too much functionality, nor the view. I believe that the logic should really be in the controller class, since this is one of the cornerstones of the MVC-pattern. But the big question is: How should you divide the controller of a MVC-implementation into smaller manageable pieces? (Applies to MVC in iOS in this case) There might be a general pattern for solving this, although I am specifically looking for a solution for iOS. Please give an example of a good pattern for solving this issue. Please provide an argument why your solution is awesome.

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  • Is switch-case over enumeration bad practice?

    - by Puckl
    I have an enumeration with the commands Play, Stop and Pause for a media player. In two classes I do a switch-case over the received commands. The player runs in a different thread and I deliver the commands in a command queue to the thread. If I generate class diagrams the enumeration has dependencies all over the place. Is there a nicer way to deal with the commands? If I would change/extend the enumeration, I would have to change several classes. (Its not super important to keep the player extensible, but I try to write nice software.)

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  • Conditions for a traditional friends system vs. open following system

    - by Dan
    I'm just curious for everyone who is developing social sites out there. When you build a method for connecting users, do you prefer to use a following-style system (follow me, you can see all of my information and I can just choose to follow you back), or instead do you choose to have a friends-style system (I have to allow you see all of my information on your homepage, even if it is open to the public, vise versa). Why and under what circumstances do you use each? How do you manage privacy between your users? Have you use another way to connect your users? Examples of what methods you've choose and how you manage the user's privacy (private by default vs open to the web) are awesome; it could show correlation and provides an actual look.

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  • Stuck at enemy movement

    - by Syed
    I am making a TD game in unity, Initially I made all of my enemy movements frame rate dependent say: I had a grid point1 at -22.65 and other at -21.1, diagrammatically: (-22.65) _________(-21.1)_______(-21.1+1.55) ...... so the distance on x axis between two points is 1.55, divided it by 25 jumps with each enemy jump of 0.062 of each frame. On reaching on next point of grid the enemy find again its path. All went fine until I have requirement of FastForward and Pause feature. I used timeScale property of unity but it wont work as they are frame dependent. I also tried double speed of enemy on clicking fast forward button at any time, it has some issues that enemy jumps are now less and it fails to reach on next grid point. Could someone suggest me solution to my problem. Do I need to change the enemy movement code to make it frame independent ?? I need the enemy to reach on the grid specific point I also need later to slow down any one enemy's speed when tower fires on it. Thnx

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  • Push or Pull Input Data In the Game Logic?

    - by Qua
    In the process of preparing my game for networking I'm adding a layer of seperation between the physical input (mouse/keyboard) and the actual game "engine"/logic. All input that has any relation to the game logic is wrapped inside action objects such as BuildBuildingAction. I was thinking of having an action processing layer that would determine what to do with the input. This layer could then be set up to either just pass the actions locally to the game engine or send it via sockets to the network server depending on whether the game was single- or multiplayer. In network games it would make sense that the player's actions should be sent to the server, but should the game logic be pulling (polling?) the data through some sort of interface or should the action processing layer be adding the actions to an input queue in the game logic code?

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  • Making an interactive 2D map

    - by Chad
    So recently I have been working on a Legend of Zelda: A Link to the Past clone, and I am wondering how I could handle certain map interactions (like cutting grass, lifting rocks, etc). The way I am currently doing the tilemap is with 2 PNGs. The first is the "tilemap" where each pixel represents a 16x16 tile and the (red, green) values are the (x, y) coords for the tile in the second PNG (the "tileset"). I am then using the blue channel to store collision data. Each tile is split into 4 8x8 tiles and represented by a 2 bit value (0 = empty, 1 = Jumpdown point, 2 = unused right now, 3 = blocking). 4 of these 2 bit values make up the full blue channel (1 byte). So collisions work great, and I am moving on to putting interactive units on the level; but I am not sure what a good way is to do it. I have experimented with spawning an entity for each grass and rock, but there are just WAY to many; FPS just dies even if I confine it to the current "zone" the user is in (for those who remember LTTP it had zones you moved between). It does make a difference that this is a browser-based JavaScript game. tl;dr: What is a good way to have an interactive map without using full blown entities for each interactive item?

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  • Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

    - by Motti Strom
    Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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  • When following SRP, how should I deal with validating and saving entities?

    - by Kristof Claes
    I've been reading Clean Code and various online articles about SOLID lately, and the more I read about it, the more I feel like I don't know anything. Let's say I'm building a web application using ASP.NET MVC 3. Let's say I have a UsersController with a Create action like this: public class UsersController : Controller { public ActionResult Create(CreateUserViewModel viewModel) { } } In that action method I want to save a user to the database if the data that was entered is valid. Now, according to the Single Responsibility Principle an object should have a single responsibility, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility. Since validation and saving to the database are two separate responsibilities, I guess I should create to separate class to handle them like this: public class UsersController : Controller { private ICreateUserValidator validator; private IUserService service; public UsersController(ICreateUserValidator validator, IUserService service) { this.validator = validator; this.service= service; } public ActionResult Create(CreateUserViewModel viewModel) { ValidationResult result = validator.IsValid(viewModel); if (result.IsValid) { service.CreateUser(viewModel); return RedirectToAction("Index"); } else { foreach (var errorMessage in result.ErrorMessages) { ModelState.AddModelError(String.Empty, errorMessage); } return View(viewModel); } } } That makes some sense to me, but I'm not at all sure that this is the right way to handle things like this. It is for example entirely possible to pass an invalid instance of CreateUserViewModel to the IUserService class. I know I could use the built in DataAnnotations, but what when they aren't enough? Image that my ICreateUserValidator checks the database to see if there already is another user with the same name... Another option is to let the IUserService take care of the validation like this: public class UserService : IUserService { private ICreateUserValidator validator; public UserService(ICreateUserValidator validator) { this.validator = validator; } public ValidationResult CreateUser(CreateUserViewModel viewModel) { var result = validator.IsValid(viewModel); if (result.IsValid) { // Save the user } return result; } } But I feel I'm violating the Single Responsibility Principle here. How should I deal with something like this?

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