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  • Is it a good idea to define a variable in a local block for a case of a switch statement?

    - by Paperflyer
    I have a rather long switch-case statement. Some of the cases are really short and trivial. A few are longer and need some variables that are never used anywhere else, like this: switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: { int specialVariable = 5; // Do something complex with specialVariable } break; } The alternative would be to declare that variable before going into the switch like this: int specialVariable = 5; switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: // Do something complex with specialVariable break; } This can get rather confusing since it is not clear to which case the variable belongs and it uses some unnecessary memory. However, I have never seen this usage anywhere else. Do you think it is a good idea to declare variables locally in a block for a single case?

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  • Where to put a piece of code in Ruby on Rails?

    - by yuval
    I have a post controller that has many comments. The post model has a field called has_comments which is a boolean (so I can quickly select from the database only posts that have comments). To create a new comment for a post, I use the create action of my comments controller. After I create the comment I need to update my post's has_comments field and set it to true. I can update this field from the create action of my comments controller, but that doesn't seem right - I feel that I should really be using the post's update action, but I'm not sure if it's right to call it (via send?) from the create action of the comments controller. Where should the code for updating the post be? Thank you!

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  • help me to choose between two designs

    - by alex
    // stupid title, but I could not think anything smarter I have a code (see below, sorry for long code but it's very-very simple): namespace Option1 { class AuxClass1 { string _field1; public string Field1 { get { return _field1; } set { _field1 = value; } } // another fields. maybe many fields maybe several properties public void Method1() { // some action } public void Method2() { // some action 2 } } class MainClass { AuxClass1 _auxClass; public AuxClass1 AuxClass { get { return _auxClass; } set { _auxClass = value; } } public MainClass() { _auxClass = new AuxClass1(); } } } namespace Option2 { class AuxClass1 { string _field1; public string Field1 { get { return _field1; } set { _field1 = value; } } // another fields. maybe many fields maybe several properties public void Method1() { // some action } public void Method2() { // some action 2 } } class MainClass { AuxClass1 _auxClass; public string Field1 { get { return _auxClass.Field1; } set { _auxClass.Field1 = value; } } public void Method1() { _auxClass.Method1(); } public void Method2() { _auxClass.Method2(); } public MainClass() { _auxClass = new AuxClass1(); } } } class Program { static void Main(string[] args) { // Option1 Option1.MainClass mainClass1 = new Option1.MainClass(); mainClass1.AuxClass.Field1 = "string1"; mainClass1.AuxClass.Method1(); mainClass1.AuxClass.Method2(); // Option2 Option2.MainClass mainClass2 = new Option2.MainClass(); mainClass2.Field1 = "string2"; mainClass2.Method1(); mainClass2.Method2(); Console.ReadKey(); } } What option (option1 or option2) do you prefer ? In which cases should I use option1 or option2 ? Is there any special name for option1 or option2 (composition, aggregation) ?

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  • Python-based password tracker (or dictionary)

    - by Arrieta
    Hello: Where we work we need to remember about 10 long passwords which need to change every so often. I would like to create a utility which can potentially save these passwords in an encrypted file so that we can keep track of them. I can think of some sort of dictionary passwd = {'host1':'pass1', 'host2':'pass2'}, etc, but I don't know what to do about encryption (absolutely zero experience in the topic). So, my question is really two questions: Is there a Linux-based utility which lets you do that? If you were to program it in Python, how would you go about it? A perk of approach two, would be for the software to update the ssh public keys after the password has been changed (you know the pain of updating ~15 tokens once you change your password). As it can be expected, I have zero control over the actual network configuration and the management of scp keys. I can only hope to provide a simple utility to me an my very few coworkers so that, if we need to, we can retrieve a password on demand. Cheers.

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  • where to store temporary data in MVC 2.0 project

    - by StuffHappens
    Hello! I'm starting to learn MVC 2.0 and I'm trying to create a site with a quiz: user is asked a question and given several options of answer. If he chooses the right answer he gets some points, if he doesn't, he looses them. I tried to do this the following way public class HomeController : Controller { private ITaskGenerator taskGenerator = new TaskGenerator(); private string correctAnswer; public ActionResult Index() { var task = taskGenerator .GenerateTask(); ViewData["Task"] = task.Task; ViewData["Options"] = task.Options; correctAnswer= task.CorrectAnswer; return View(); } public ActionResult Answer(string id) { if (id == correctAnswer) return View("Correct") return View("Incorrect"); } } But I have a problem: when user answers the cotroller class is recreated and I loose correct answer. So what is the best place to store correct answer? Should I create a static class for this purpose? Thanks for your help!

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  • Is it ok to throw NotImplemented exception in virtual methods?

    - by Axarydax
    I have a base class for some plugin-style stuff, and there are some methods that are absolutely required to be implemented. I currently declare those in the base class as virtual, for example public virtual void Save { throw new NotImplementedException(); } and in the descendand I have a public override void Save() { //do stuff } Is it a good practice to throw a NotImplementedException there? The descendand classes could for example be the modules for handling different file formats. Thanks

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  • boost.asio's socket's recieve/send functions are bad?

    - by the_drow
    Data may be read from or written to a connected TCP socket using the receive(), async_receive(), send() or async_send() member functions. However, as these could result in short writes or reads, an application will typically use the following operations instead: read(), async_read(), write() and async_write(). I don't really understand that remark as read(), async_read(), write() and async_write() can also end up in short writes or reads, right? Why are those functions not the same? Should I use them at all? Can someone clarify that remark for me?

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  • Rapid Opening and Closing System.IO.StreamWriter in C#

    - by ccomet
    Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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  • Should I use block identifiers ("end;") in my code?

    - by JosephStyons
    Code Complete says it is good practice to always use block identifiers, both for clarity and as a defensive measure. Since reading that book, I've been doing that religiously. Sometimes it seems excessive though, as in the case below. Is Steve McConnell right to insist on always using block identifiers? Which of these would you use? //naughty and brief with myGrid do for currRow := FixedRows to RowCount - 1 do if RowChanged(currRow) then if not(RecordExists(currRow)) then InsertNewRecord(currRow) else UpdateExistingRecord(currRow); //well behaved and verbose with myGrid do begin for currRow := FixedRows to RowCount - 1 do begin if RowChanged(currRow) then begin if not(RecordExists(currRow)) then begin InsertNewRecord(currRow); end //if it didn't exist, so insert it else begin UpdateExistingRecord(currRow); end; //else it existed, so update it end; //if any change end; //for each row in the grid end; //with myGrid

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  • SELECT product from subclass: How many queries do I need?

    - by Stefano
    I am building a database similar to the one described here where I have products of different type, each type with its own attributes. I report a short version for convenience product_type ============ product_type_id INT product_type_name VARCHAR product ======= product_id INT product_name VARCHAR product_type_id INT -> Foreign key to product_type.product_type_id ... (common attributes to all product) magazine ======== magazine_id INT title VARCHAR product_id INT -> Foreign key to product.product_id ... (magazine-specific attributes) web_site ======== web_site_id INT name VARCHAR product_id INT -> Foreign key to product.product_id ... (web-site specific attributes) This way I do not need to make a huge table with a column for each attribute of different product types (most of which will then be NULL) How do I SELECT a product by product.product_id and see all its attributes? Do I have to make a query first to know what type of product I am dealing with and then, through some logic, make another query to JOIN the right tables? Or is there a way to join everything together? (if, when I retrieve the information about a product_id there are a lot of NULL, it would be fine at this point). Thank you

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  • Returning back to the results after editing

    - by Parhs
    Hello, I am developing an application which has several CRUD actions... I am using Java and i am forced to use Struts framework. My problem is: I have a search page which returns some results.The user can click at a result and then he goes to another edit-page... He may apply changes or not...What i need is a way to return at the result page again and at the same scroll position.Javascript must be enabled for this project however.. I am wondering which is the best practice to achieve this effect... A solution would be to save the last search URL but i know that this wouldnt work if the user has multiple results. I know how to do it but i am lloking for a good practice!

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  • What is the reason not to use select * ?

    - by Chris Lively
    I've seen a number of people claim that you should specifically name each column you want in your select query. Assuming I'm going to use all of the columns anyway, why would I not use SELECT *? Even considering the question from 9/24, I don't think this is an exact duplicate as I'm approaching the issue from a slightly different perspective. One of our principles is to not optimize before it's time. With that in mind, it seems like using SELECT * should be the preferred method until it is proven to be a resource issue or the schema is pretty much set in stone. Which, as we know, won't occur until development is completely done. That said, is there an overriding issue to not use SELECT *?

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  • How to differentiate between exceptions i can show the user, and ones i can't?

    - by Ian Boyd
    i have some business logic that traps some logically invalid situations, e.g. trying to reverse a transaction that was already reversed. In this case the correct action is to inform the user: Transaction already reversed or Cannot reverse a reversing transaction or You do not have permission to reverse transactions or This transaction is on a session that has already been closed or This transaction is too old to be reversed The question is, how do i communicate these exceptional cases back to the calling code, so they can show the user? Do i create a separate exception for each case: catch (ETransactionAlreadyReversedException) MessageBox.Show('Transaction already reversed') catch (EReversingAReversingTransactionException) MessageBox.Show('Cannot reverse a reversing transaction') catch (ENoPermissionToReverseTranasctionException) MessageBox.Show('You do not have permission to reverse transactions') catch (ECannotReverseTransactionOnAlredyClosedSessionException) MessageBox.Show('This transaction is on a session that has already been closed') catch (ECannotReverseTooOldTransactionException) MessageBox.Show('This transaction is too old to be reversed') Downside for this is that when there's a new logical case to show the user: Tranasctions created by NSL cannot be reversed i don't simply show the user a message, and instead it leaks out as an unhandled excpetion, when really it should be handled with another MessageBox. The alternative is to create a single exception class: `EReverseTransactionException` With the understanding that any exception of this type is a logical check, that should be handled with a message box: catch (EReverseTransactionException) But it's still understood that any other exceptions, ones that involve, for example, an memory ECC parity error, continue unhandled. In other words, i don't convert all errors that can be thrown by the ReverseTransaction() method into EReverseTransactionException, only ones that are logically invalid cause of the user.

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  • How do you handle multiple (overlapping) projects in trac?

    - by Oliver Giesen
    We are using trac and are really satisfied with it. However, out of the box, trac is best suited for single-project environments only. I'd be interested to hear about the various approaches people take to make it work with multiple projects nevertheless and their experiences with them. Are there any plugins to recommend? Any patches, tweaks or whatnots? Are you maybe even using an entirely different bug-tracking system that offers all of trac's functionality plus multi-project support? We recently started managing a second project ourselves which generally works okay but also has some drawbacks, especially where the two projects overlap because of common library code we wrote that is used in both projects. How do you handle this? (I'll attach our own current approach as an answer to this post.)

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  • Where to place the login/authentication related actions in MVC

    - by rogeriopvl
    I've searched around and found that when implementing an authentication module in MVC architecture some people opt to place the login related actions in the User controller while others place it in a controller dedicated to authentication only. In pseudo-java-like code: class UserController extends Controller { public login() { //... } } Accessed with http://mydomain.com/user/login. vs. class AuthController extends Controller { public login() { //... } } Accessed with http://mydomain.com/auth/login. I would like to know which approach is better, and why. That is, if there's really any difference at all. Thanks in advance.

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  • Hibernate many-to-one - bad usage?

    - by DaveA
    Just trying out Hibernate (with Annotations) and I'm having problems with my mappings. I have two entity classes, AudioCD and Artist. @Entity public class AudioCD implements CatalogItem { @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; private String title; @ManyToOne(cascade = { CascadeType.ALL }, optional = false) private Artist artist; .... } @Entity @Table(uniqueConstraints = { @UniqueConstraint(columnNames = { "name" }) }) public class Artist { @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; @Column(nullable = false) private String name; ..... } I get AudioCD objects from an external source. When I try to persist the AudioCD the Artist gets persisted as well, just like I want to happen. If I try persisting another different CD, but Artist already exists I get errors due to constraint violations. I want Hibernate to recognise that the Artist already exists and shouldn't be inserted again. Can this be done via annotations? Or do I have to manage the persistence of the AudioCD and Artist seperately?

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  • Should every class have its own namespace?

    - by thehouse
    Something that has been troubling me for a while: The current wisdom is that types should be kept in a namespace that only contains functions which are part of the type's non-member interface (see C++ Coding Standards Sutter and Alexandrescu or here) to prevent ADL pulling in unrelated definitions. Does this imply that all classes must have a namespace of their own? If we assume that a class may be augmented in the future by the addition of non-member functions, then it can never be safe to put two types in the same namespace as either one of them may introduce non-member functions that could interfere with the other. The reason I ask is that namespaces are becoming cumbersome for me. I'm writing a header-only library and I find myself using classes names such as project::component::class_name::class_name. Their implementations call helper functions but as these can't be in the same namespace they also have to be fully qualified!

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  • Why doesn't String's hashCode() cache 0?

    - by polygenelubricants
    I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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  • Is there any difference between var name = function() {} & function name() {} in Javascript?

    - by Fletcher Moore
    Suppose we are inside a function and not in the global namespace. function someGlobalFunction() { var utilFunction1 = function() { } function utilFunction2 () { } utilFunction1(); utilFunction2(); } Are these synonymous? And do these functions completely cease to exist when someGlobalFunction returns? Should I prefer one or the other for readability or some other reason?

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  • Guidelines for LBS Mobile application development

    - by Suriyan Suresh
    i need some help!, i am planning to develop such LBS Mobile Application which find nearest things based on gps data from mobile. 1.what are the best free and (preferably) open source technologies for development?. 2.What programming language to use for development of such application?. 3.what are the points to be considered? I need the general overview of the requirements for planning, I was interested in having a general understanding of the data, tools, and frameworks required to accomplish the job.

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  • how can I "force" a branch upon the trunk, in the case I can't "reintegrate"?

    - by davka
    We created a branch from the trunk on which a major refactoring was done. Meanwhile, the trunk advanced a few revisions with some fixes. We don't want these changes on the branch, so we don't want to "catch-up" merge the trunk to the branch, because we don't want to mix the old and new code. But without this I can't reintegrate the branch back to the trunk. Is there a way to impose the branch on the trunk "as-is"? (an idea I considered is to undo ("reverse-merge") the trunk back to the revision where the branch started, and then it is safe to merge it on branch - nothing should happen. Then I can reintegrate. What do you think?) thanks!

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