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  • How important is managing memory in Objective-C?

    - by Alex Mcp
    Background: I'm (jumping on the bandwagon and) starting learning about iPhone/iPad development and Objective-C. I have a great background in web development and most of my programming is done in javascript (no libraries), Ruby, and PHP. Question: I'm learning about allocating and releasing memory in Objective-C, and I see it as quite a tricky task to layer on top of actually getting the farking thing to run. I'm trying to get a sense of applications that are out there and what will happen with a poorly memory-managed program. A) Are apps usually released with no memory leaks? Is this a feasible goal, or do people more realistically just excise the worst offenders and that's ok? B) If I make an NSString for a title of a view, let's say, and forget to deallocate it it, does this really only become a problem if I recreate that string repeatedly? I imagine what I'm doing is creating an overhead of the memory needed to store that string, so it's probably quite piddling (a few bytes?) However if I have a rapidly looping cycle in a game that 'leaks' an int every cycle or something, that would overflow the app quite quickly. Are these assumptions correct? Sorry if this isn't up the community-wiki alley, I'm just trying to get a handle on how to think about memory and how careful I'll need to be. Any anecdotes or App Store-submitted app experiences would be awesome to hear as well.

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  • How many files in a directory is too many?

    - by Kip
    Does it matter how many files I keep in a single directory? If so, how many files in a directory is too many, and what are the impacts of having too many files? (This is on a Linux server.) Background: I have a photo album website, and every image uploaded is renamed to an 8-hex-digit id (say, a58f375c.jpg). This is to avoid filename conflicts (if lots of "IMG0001.JPG" files are uploaded, for example). The original filename and any useful metadata is stored in a database. Right now, I have somewhere around 1500 files in the images directory. This makes listing the files in the directory (through FTP or SSH client) take a few seconds. But I can't see that it has any affect other than that. In particular, there doesn't seem to be any impact on how quickly an image file is served to the user. I've thought about reducing the number of images by making 16 subdirectories: 0-9 and a-f. Then I'd move the images into the subdirectories based on what the first hex digit of the filename was. But I'm not sure that there's any reason to do so except for the occasional listing of the directory through FTP/SSH.

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  • Exercise 26 of The Pragmatic Programmer

    - by _ande_turner_
    There is a code snippet presented in The Pragmatic Programmer on page 143 as: public class Colada { private Blender myBlender; private Vector myStuff; public Colada() { myBlender = new Blender(); myStuff = new Vector(); } private doSomething() { myBlender.addIngredients(myStuff.elements()); } } This obeys the Law of Demeter / Principle of Least Knowledge. Is it preferable to, and are there any caveats for, replacing it with the following, which utilises Dependency Injection? public class Colada throws IllegalArgumentException { private Blender myBlender; private Vector myStuff; public Colada(Blender blender, Vector stuff) { blender == null ? throw new IllegalArgumentException() : myBlender = blender; stuff == null ? throw new IllegalArgumentException() : myStuff = stuff; } public getInstance() { Blender blender = new Blender(); Vector stuff = new Vector(); return new Colada(blender, stuff); } private doSomething() { myBlender.addIngredients(myStuff.elements()); } }

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  • Is it a good practice to suppress warnings?

    - by Chris Cooper
    Sometimes while writing Java in Eclipse, I write code that generates warnings. A common one is this, which I get when extending the Exception class: public class NumberDivideException extends Exception { public NumberDivideException() { super("Illegal complex number operation!"); } public NumberDivideException(String s) { super(s); } } // end NumberDivideException The warning: The serializable class NumberDivideException does not declare a static final serialVersionUID field of type long. I know this warning is caused by my failure to... well, it says right above. I could solve it by including the serialVersionUID, but this is a one hour tiny assignment for school; I don't plan on serializing it anytime soon... The other option, of course, is to let Eclipse add @SuppressWarnings("serial"). But every time my mouse hovers over the Suppress option, I feel a little guilty. For programming in general, is it a good habit to suppress warnings? (Also, as a side question, is adding a "generated" serialVersionUID like serialVersionUID = -1049317663306637382L; the proper way to add a serialVersionUID, or do I have to determine the number some other way?)

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  • When to use UserControl vs. Control in Silverlight?

    - by Dov
    I'm just getting my feet wet in Silverlight, and don't really understand the differences and pros/cons of creating a UserControl vs. creating a Control for the same task (as in when you right click on a selection in Expression Blend, for instance). It seems like selecting "Make Into Control" just creates a new template for the base type you specify, whereas creating a UserControl creates a whole new base class. Is that correct? In this particular instance, I'm creating a custom text box control that only takes numbers, and divides itself into 3 sections, storing 3 values into separate properties as pictured below. In this particular case, which would be best? Update (Additional Question): Why can't I use Template Binding with a UserControl, but I can with a Control? That's one reason I thought that making a UserControl might not be the right decision.

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  • What is your best-practice advice on implementing SQL stored procedures (in a C# winforms applicatio

    - by JYelton
    I have read these very good questions on SO about SQL stored procedures: When should you use stored procedures? and Are Stored Procedures more efficient, in general, than inline statements on modern RDBMS’s? I am a beginner on integrating .NET/SQL though I have used basic SQL functionality for more than a decade in other environments. It's time to advance with regards to organization and deployment. I am using .NET C# 3.5, Visual Studio 2008 and SQL Server 2008; though this question can be regarded as language- and database- agnostic, meaning that it could easily apply to other environments that use stored procedures and a relational database. Given that I have an application with inline SQL queries, and I am interested in converting to stored procedures for organizational and performance purposes, what are your recommendations for doing so? Here are some additional questions in my mind related to this subject that may help shape the answers: Should I create the stored procedures in SQL using SQL Management Studio and simply re-create the database when it is installed for a client? Am I better off creating all of the stored procedures in my application, inside of a database initialization method? It seems logical to assume that creating stored procedures must follow the creation of tables in a new installation. My database initialization method creates new tables and inserts some default data. My plan is to create stored procedures following that step, but I am beginning to think there might be a better way to set up a database from scratch (such as in the installer of the program). Thoughts on this are appreciated. I have a variety of queries throughout the application. Some queries are incredibly simple (SELECT id FROM table) and others are extremely long and complex, performing several joins and accepting approximately 80 parameters. Should I replace all queries with stored procedures, or only those that might benefit from doing so? Finally, as this topic obviously requires some research and education, can you recommend an article, book, or tutorial that covers the nuances of using stored procedures instead of direct statements?

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  • Using nullable types in C#

    - by Martin Brown
    I'm just interested in people's opinions. When using nullable types in C# what is the best practice way to test for null: bool isNull = (i == null); or bool isNull = !i.HasValue; Also when assigning to a non-null type is this: long? i = 1; long j = (long)i; better than: long? i = 1; long j = i.Value;

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  • C# Static constructors design problem - need to specify parameter

    - by Neil Dobson
    I have a re-occurring design problem with certain classes which require one-off initialization with a parameter such as the name of an external resource such as a config file. For example, I have a corelib project which provides application-wide logging, configuration and general helper methods. This object could use a static constructor to initialize itself but it need access to a config file which it can't find itself. I can see a couple of solutions, but both of these don't seem quite right: 1) Use a constructor with a parameter. But then each object which requires corelib functionality should also know the name of the config file, so this has to be passed around the application. Also if I implemented corelib as a singleton I would also have to pass the config file as a parameter to the GetInstance method, which I believe is also not right. 2) Create a static property or method to pass through the config file or other external parameter. I have sort of used the latter method and created a Load method which initializes an inner class which it passes through the config file in the constructor. Then this inner class is exposed through a public property MyCoreLib. public static class CoreLib { private static MyCoreLib myCoreLib; public static void Load(string configFile) { myCoreLib = new MyCoreLib(configFile); } public static MyCoreLib MyCoreLib { get { return myCoreLib; } } public class MyCoreLib { private string configFile; public MyCoreLib(string configFile) { this.configFile = configFile; } public void DoSomething() { } } } I'm still not happy though. The inner class is not initialized until you call the load method, so that needs to be considered anywhere the MyCoreLib is accessed. Also there is nothing to stop someone calling the load method again. Any other patterns or ideas how to accomplish this?

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  • Does multiple cpp files correspond to multiple compilation units?

    - by Rahul
    Hello All, Suppose, we have a big Class. and we don't want to break it. In order to maintain code suppose we have created a multiple example1.cpp, example2.cpp, example3.cpp files for single example.h file for class cexample. Does this correspond to multiple compilations units? What is the best approach to handle such big classes? Any suggestions and comments are appreciated. Thank you, RAHUL

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  • To HTML 5 or not HTML 5 ?

    - by ZX12R
    I am a designer whose main marketing strategy is multi browser compatibility. I assure my clients that the site will work even in IE6 (!). Of late i have been pondering over the question of moving to HTML 5. The reason behind my apprehension is that IE6 is still a major player in terms of market share and i don't want to lose it. Is there any way of moving to HTML 5 and still promise multi browser compatibility? Thank you.

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  • Best practice for controlling a busy GUI

    - by MPelletier
    Suppose a GUI (C#, WinForms) that performs work and is busy for several seconds. It will still have buttons that need to remain accessible, labels that will change, progress bars, etc. I'm using this approach currently to change the GUI when busy: //Generic delegates private delegate void SetControlValue<T>(T newValue); //... public void SetStatusLabelMessage(string message) { if (StatusLabel.InvokeRequired) StatusLabel.BeginInvoke(new SetControlValue<string>(SetStatusLabelMessage, object[] { message }); else StatusLabel.Text = message; } I've been using this like it's going out of style, yet I'm not quite certain this is proper. Creating the delegate (and reusing it) makes the whole thing cleaner (for me, at least), but I must know that I'm not creating a monster...

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  • Recommended (remote) backup technique for SQL Compact?

    - by Cool Jon
    Hello. Is there a generally recommended approach to backing up an SQL CE/SQLite database over the Internet? The client source is .NET/Windows based, the backup destination runs Ubuntu. I am using a small SQL CE database and have been trying to figure out the most reasonable approach to doing this. The file size (in terms of transfer time/bandwidth) isn't a big deal. I had a look around, and so far the things I've given thought are: Online backup services (Dropbox, Mozy) Opening an FTP/SFTP connection Writing a custom protocol with public/private keys Unsure regarding #1 because I doubt they would like it if somebody transferred gigabytes of data using a POST; and they do not seem to offer native (or .NET) APIs. FTP/SFTP seems risky in terms of security and privileges (as the password/key would need to be stored on the client side). With the right user group/user privileges this may work. Custom protocol seems overkill, which is why I am hoping somebody has already defined a reasonable API for language/platform-independent backups over the Internet. Any hints S.O.?

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  • pointer as second argument instead of returning pointer?

    - by Tyler
    I noticed that it is a common idiom in C to accept an un-malloced pointer as a second argument instead of returning a pointer. Example: /*function prototype*/ void create_node(node_t* new_node, void* _val, int _type); /* implementation */ node_t* n; create_node(n, &someint, INT) Instead of /* function prototype */ node_t* create_node(void* _val, int _type) /* implementation */ node_t* n = create_node(&someint, INT) What are the advantages and/or disadvantages of both approaches? Thanks!

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  • HowTo Crypt/Encrypt some string (e.g. Password) on Qt simple

    - by mosg
    Hi. Here what I have got: Qt SDK version 4.6.2 Windows XP Question: how can I simply crypt and encrypt simple QString value? I need this to be able to save some crypted string into the INI file, and after reopening application encrypt string to normal password string value. PS: I'm looking simple and nice solution. Thanks for help!

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  • Accommodating hierarchical data in SQL Server 2005 database design

    - by Remnant
    Context I am fairly new to database design (=know the basics) and am grappling with how best to design my database for a project I am currently working on. In short, my database will keep a log of which employees have attended certain health and safety courses throughout the year. There are multiple types of course e.g. moving objects, fire safety, hygiene etc. In terms of my database design I need to accommodate the following: Each location can have multiple divisions Each division can have multiple departments Each department can have multiple functions Each function can have multiple job roles Each job role can have different course requirements Also note that the structure at each location may not be the same e.g. the departments within divisions are not the same across locations and the functions within departments may also differ. Edit - updated to better articulate problem Let's assume I am just looking at Location, Division and Department and I have my database as follows: LocationTable DivisionTable DepartmentTable LocationID(PK) DivisionID(PK) DepartmentID(PK) LocationName DivisionName DepartmentName There is a many-to-many relationship between Locations and Divisions and also between Departments and Divisions. Suppose I set up a 'Junction Table' as follows: Location_Division LocationID(FK) DivisionID(FK) Using Location_Division I could easily pull back the Divisions for any Location. However, suppose I want to pull back all departments for a given Division in a given Location. If I set up another 'Junction Table' for Division and Department then I can't see how I would differentiate Division by Location? Division_Department DivisionID(FK) DepartmentID(FK) Location_Division Division_Department LocationID DivisionID DivisionID DepartmentID 1 1 1 1 1 2 1 2 2 1 2 1 2 2 2 2 Do I need to expand the number of columns in my 'Junction Table' e.g. Location_Division_Department LocationID(FK) DivisionID(FK) DepartmentID(FK) Location_Division_Department LocationID DivisionID DepartmentID 1 1 1 1 1 2 1 1 3 2 1 1 2 1 2 2 1 3

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  • Asp.Net Program Architecture

    - by Pino
    I've just taken on a new Asp.Net MVC application and after opening it up I find the following, [Project].Web [Project].Models [Project].BLL [Project].DAL Now, something thats become clear is that there is the data has to do a hell of a lot before it makes it to the View (DatabaseDALRepoBLLConvertToModelControllerView). The DAL is Subsonic, the repositorys in the DAL return the subsonic entities to the BLL which process them does crazy things and converts them into a Model (From the .Models) sometimes with classes that look like this public DataModel GetDataModel(EntityObject Src) { var ReturnData = new DataModel(): ReturnData.ID = Src.ID; ReturnDate.Name = Src.Name; //etc etc } Now, the question is, "Is this complete overkill"? Ok the project is of a decent size and can only get bigger but is it worth carrying on with all this? I dont want to use AutoMapper as it just seems like it makes the complication worse. Can anyone shed any light on this?

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  • Objective C selector memory managment (does this leak memory)?

    - by James Jones
    - (IBAction) someButtonCall { if(!someCondition) { someButtonCallBack = @selector(someButtonCall); [self presentModalViewController:someController animated:YES]; } else ... } //Called from someController - (void) someControllerFinished:(BOOL) ok { [self dismissModalViewControllerAnimated:YES]; if(ok) [self performSelector:someButtonCallBack]; else ... } I'm wondering if the user keeps getting into the !someCondition clause if the selector is leaked by assigning a new selector each time (the code above is hypothetical and not what i'm doing). Any help is appreciated. Thanks, James Jones

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  • Best practice for submits redirecting to another page in MVC2?

    - by blesh
    I have a situation with my MVC2 app where I have multiple pages that need to submit different information, but all need to end up at the same page. In my old Web Forms app, I'd have just accomplished this in my btnSave_Click delegate with a Redirect. There are three different types of products, each of which need to be saved to the cart in a completely different manner from their completely different product pages. I'm not going to get into why or how they're different, just suffice to say, they're totally different. After they're saved to the cart, I need to "redirect" to the Checkout view. But it should be noted, that you can also just browse straight to the Checkout view without having to submit any products to add to the cart. Here's a diagram of what I'm trying to accomplish, and how I think I need to handle it: Is this correct? It seems like a common scenario, but I haven't seen any examples of how I should handle this. Thank you all in advance.

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  • SQL Server 2005 database design - many-to-many relationships with hierarchy

    - by Remnant
    Note I have completely re-written my original post to better explain the issue I am trying to understand. I have tried to generalise the problem as much as possible. Also, my thanks to the original people who responded. Hopefully this post makes things a little clearer. Context In short, I am struggling to understand the best way to design a small scale database to handle (what I perceive to be) multiple many-to-many relationships. Imagine the following scenario for a company organisational structure: Textile Division Marketing Division | | ---------------------- ---------------------- | | | | HR Dept Finance Dept HR Dept Finance Dept | | | | ---------- ---------- ---------- --------- | | | | | | | | Payroll Hiring Audit Tax Payroll Hiring Audit Accounts | | | | | | | | Emps Emps Emps Emps Emps Emps Emps Emps NB: Emps denotes a list of employess that work in that area When I first started with this issue I made four separate tables: Divisions - Textile, Marketing (PK = DivisionID) Departments - HR, Finance (PK = DeptID) Functions - Payroll, Hiring, Audit, Tax, Accounts (PK = FunctionID) Employees - List of all Employees (PK = EmployeeID) The problem as I see it is that there are multiple many-to-many relationships i.e. many departments have many divisions and many functions have many departments. Question Giving the database structure above, suppose I wanted to do the following: Get all employees who work in the Payroll function of the Marketing Division To do this I need to be able to differentiate between the two Payroll departments but I am not sure how this can be done? I understand that I could build a 'Link / Junction' table between Departments and Functions so that I can retrieve which Functions are in which Departments. However, I would still need to differentiate the Division they belong to. Research Effort As you can see I am an abecedarian when it comes to database deisgn. I have spent the last two days resaerching this issue, traversing nested set models, adjacency models, reading that this issue is known not to be NP complete etc. I am sure there is a simple solution?

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  • Reference for proper handling of PID file on Unix

    - by bignose
    Where can I find a well-respected reference that details the proper handling of PID files on Unix? On Unix operating systems, it is common practice to “lock” a program (often a daemon) by use of a special lock file: the PID file. This is a file in a predictable location, often ‘/var/run/foo.pid’. The program is supposed to check when it starts up whether the PID file exists and, if the file does exist, exit with an error. So it's a kind of advisory, collaborative locking mechanism. The file contains a single line of text, being the numeric process ID (hence the name “PID file”) of the process that currently holds the lock; this allows an easy way to automate sending a signal to the process that holds the lock. What I can't find is a good reference on expected or “best practice” behaviour for handling PID files. There are various nuances: how to actually lock the file (don't bother? use the kernel? what about platform incompatibilities?), handling stale locks (silently delete them? when to check?), when exactly to acquire and release the lock, and so forth. Where can I find a respected, most-authoritative reference (ideally on the level of W. Richard Stevens) for this small topic?

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  • JavaScript: Keeping track of eventListeners on DOM elements

    - by bobthabuilda
    What is the best way to keep track of eventListener functions on DOM elements? Should I add a property to the element which references the function like this: var elem = document.getElementsByTagName( 'p' )[0]; function clickFn(){}; elem.listeners = { click: [clickFn, function(){}] }; elem.addEventListener( 'click', function(e){ clickFn(e); }, false ); Or should I store it in my own variable in my code like below: var elem = document.getElementsByTagName( 'p' )[0]; function clickFn(){}; // Using window for the sake of brevity, otherwise I wouldn't =D // DOM elements and their listeners are referenced here in a paired array window.listeners = [elem, { click: [clickFn, function(){}] }]; elem.addEventListener( 'click', function(e){ clickFn(e); }, false ); Obviously the second method would be less obtrusive, but it seems it could get intensive iterating through all those possibilities. Which is the best way and why? Is there a better way?

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  • What is the correct way to import and export out of Excel to SQL Server and back?

    - by Vecdid
    Looking for the correct way and control to import and export of out of Microsoft Excel programmatically. I am willing to get a 3rd party control that supports this functionality, or I can create it myself, but looking to get this prioject done fast. The Datasource will be offline. Although when it is online for the upload/download if there is a control that would merge them, that would work also. But best is to remain offline, don't need the support headache. Security is also an issue. SSIS is not available on the shared database server. The website that hosts the asp.net application is not on the same machine as the sql server. Thank you.

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