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  • Rails Model has_many with multiple foreign_keys

    - by Kenzie
    Relatively new to rails and trying to model a very simple family "tree" with a single Person model that has a name, gender, father_id and mother_id (2 parents). Below is basically what I want to do, but obviously I can't repeat the :children in a has_many (the first gets overwritten). class Person < ActiveRecord::Base belongs_to :father, :class_name => 'Person' belongs_to :mother, :class_name => 'Person' has_many :children, :class_name => 'Person', :foreign_key => 'mother_id' has_many :children, :class_name => 'Person', :foreign_key => 'father_id' end Is there a simple way to use has_many with 2 foreign keys, or maybe change the foreign key based on the object's gender? Or is there another/better way altogether? Thanks!

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  • Examples of both beautiful and ugly java code?

    - by tputkonen
    I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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  • What's the best practice for handling system-specific information under version control?

    - by Joe
    I'm new to version control, so I apologize if there is a well-known solution to this. For this problem in particular, I'm using git, but I'm curious about how to deal with this for all version control systems. I'm developing a web application on a development server. I have defined the absolute path name to the web application (not the document root) in two places. On the production server, this path is different. I'm confused about how to deal with this. I could either: Reconfigure the development server to share the same path as the production Edit the two occurrences each time production is updated. I don't like #1 because I'd rather keep the application flexible for any future changes. I don't like #2 because if I start developing on a second development server with a third path, I would have to change this for every commit and update. What is the best way to handle this? I thought of: Using custom keywords and variable expansion (such as setting the property $PATH$ in the version control properties and having it expanded in all the files). Git doesn't support this because it would be a huge performance hit. Using post-update and pre-commit hooks. Possibly the likely solution for git, but every time I looked at the status, it would report the two files as being changed. Not really clean. Pulling the path from a config file outside of version control. Then I would have to have the config file in the same location on all servers. Might as well just have the same path to begin with. Is there an easy way to deal with this? Am I over thinking it?

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  • adding org.springframework.test package to spring-2.5.6-SEC01.jar in netbeans

    - by John
    This is probably very simple, however I can't get this to work. I want to use AbstractDependencyInjectionSpringContextTest class which is in org.springframework.test package. This package is not included in Netbeans' spring library, so I want to add it. So what I have tried so far is: copy and paste "test" directory (downloaded from spring) into the Netbeans' spring-2.5.6-SEC01.jar file (copy it to org.springframework directory in that jar so I can use org.springframework.test to import it). If I go to project/libraries in Netbeans it is there, but when I try to import org.springframework.test.*; the autocomplition doesn't give me the option to choose test directory from org.soringframework package. create a new library which points to "test" directory and add it to the project- as there is no any jar file in "test" I'm not sure what path should I use to import it. I'm pretty sure this is something very simple but I'm still a novice and can't figure this out.

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  • How to close and open access to SQL Server 2008 in Windows application?

    - by hgulyan
    Hi, I have a MS Access 97 application (but the question is general) working directly with SQL Server 2008 (without application server or anything). Numbers of users can be up to 1000. Windows Authentication is used. The question is: How to handle modes, so some users will be allowed to work in read-only mode some users won't have access to db for some time My versions: Using a table with a mode id for every group of users, that will work the same way. On Form Load application will query that table for mode id. Using trigger on the tables, that must work according to that mode. The trigger will query mode value and doesn't work if access is closed or it's in read-only mode I know these are not the best solutions, that's why I'm asking for your advice. There's one more point. If the mode is changed to "access-is-closed" for a group of users, that group must not be able to query to DB starting that moment. With first solution I wrote it won't work, because user can be in application at that moment and no form load event will work. How can I do this? Is there any optimal solution? Thank you. Any help would be appreciated.

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  • c++: use a #define in printf?

    - by John
    I was wanting to use a constant of some kind for the application ID (so I can use it in printf). I had this: #define _APPID_ "Hello World!" And then the simple printf, calling it into %s (string). It put this out: simple.cpp:32: error: cannot convert ‘_IO_FILE*’ to ‘const char*’ for argument ‘1’ to ‘int printf(const char*, ...)’ What would I use to define the application ID to use in printf? I tried: static const char _APPID_[] = "Hello World"` but it didn't work, same error I think.

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  • I have a bunch of template parameters that I want to hide from my users. How can I do this?

    - by Alex
    I have a superclass which is defined in terms of a few internal types it uses. Subclassing is performed as so: template <class InternalType1, class InternalType2> class Super { ... } class Sub : Super <interalTypeClass1, interalTypeClass2> { ... } But when I want to write a function that takes a pointer to the superclass, this happens : template <class InternalType1, class InternalType2> void function(Super<InternalType1, InternalType2>* in) { ... } The user really shouldn't know anything about the inside classes, and should really just concern himself with the use of the function. Some of these template lists become very very large, and expecting the user to pass them every time is wasteful, in my opinion. Any suggestions? EDIT: The function needs to know the internal types in use, so unless there is a way to access template types at compile time, I think there is no solution? Potential solution: Have each class do the following: #define SubTemplateArgs <SubTypeName, SubInternalType1, SubInternalType2> ?

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  • Activiti Engine: Task Event - User is null

    - by sockeqwe
    I have a problem, which should be simple to solve, but i can't find the method to call to solve this problem: My problem is, that every Task Event (org.activiti.engine.task.Event) returnes null by calling Event.getUserId(); If I take a look into the database I see that the database table ACT_HI_COMMENT has null as value for the column USER_ID_ for every row. I generate these TaskEvents programmatically by calling (for example) processEngine.getTaskService().addComment(task.getId(), null, commentMessage); processEngine.getTaskService().addUserIdentityLink(task.getId(), user.getId(), IDENTITY_LINK_OBSERVER); I guess there is a simple method that I must call to solve this problem, something like processEngine.setCurrentUser(authenticatedUser.getId()); Any suggestions?

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  • Does "Value Restriction" practically mean that there is no higher order functional programming?

    - by Sadache
    Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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  • lists searches in SYB or uniplate haskell

    - by Chris
    I have been using uniplate and SYB and I am trying to transform a list For instance type Tree = [DataA] data DataA = DataA1 [DataB] | DataA2 String | DataA3 String [DataA] deriving Show data DataB = DataB1 [DataA] | DataB2 String | DataB3 String [DataB] deriving Show For instance, I would like to traverse my tree and append a value to all [DataB] So my first thought was to do this: changeDataB:: Tree -> Tree changeDataB = everywhere(mkT changeDataB') chanegDataB'::[DataB] -> [DataB] changeDataB' <add changes here> or if I was using uniplate changeDataB:: Tree -> Tree changeDataB = transformBi changeDataB' chanegDataB'::[DataB] -> [DataB] changeDataB' <add changes here> The problem is that I only want to search on the full list. Doing either of these searches will cause a search on the full list and all of the sub-lists (including the empty list) The other problem is that a value in [DataB] may generate a [DataB], so I don't know if this is the same kind of solution as not searching chars in a string. I could pattern match on DataA1 and DataB3, but in my real application there are a bunch of [DataB]. Pattern matching on the parents would be extensive. The other thought that I had was to create a data DataBs = [DataB] and use that to transform on. That seems kind of lame, there must be a better solution.

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  • Not a statement?

    - by abelenky
    I have a simple little code fragment that is frustrating me: HashSet<long> groupUIDs = new HashSet<long>(); groupUIDs.Add(uid)? unique++ : dupes++; At compile time, it generates the error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement HashSet.Add is documented to return a bool, so the ternary (?) operator should work, and this looks like a completely legitimate way to track the number of unique and duplicate items I add to a hash-set. When I reformat it as a if-then-else, it works fine. Can anyone explain the error, and if there is a way to do this as a simple ternary operator?

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  • What object called a method in Obj-C

    - by Loz
    Hi, I am looking to write a plugin controller in Cocoa that loads bundles, and exposes a specific set of methods for the plugins to call. My question is this: is it possible to know (any) info about the object that called a method in the controller. When an instantiated plugin calls a method in my plugin controller, I would like to know which of the plugin instances called the method, without having to rely on the plugin sending a pointer to itself as a parameter (I could always validate the pointer they send, but I want to keep the API methods as simple as possible). There may be no perfect solution (and there are simple workarounds), but it's always good to learn some new tricks if possible (or the reasons why it's impossible). Thanks in advance.

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  • How to format JSON Date?

    - by Mark Struzinski
    I'm taking my first crack at AJAX with jQuery. I'm getting my data onto my page, but I'm having some trouble with the JSON that is returned for Date data types. Basically, I'm getting a string back that looks like this: /Date(1224043200000)/ From a total newbie at JSON - How do I format this to a short date format? Should this be handled somewhere in the jQuery code? I've tried the jQuery.UI.datepicker plugin using $.datepicker.formatDate() wiuth no success. FYI: Here's the solution I came up with using a combination of the answers here: function getMismatch(id) { $.getJSON("Main.aspx?Callback=GetMismatch", { MismatchId: id }, function(result) { $("#AuthMerchId").text(result.AuthorizationMerchantId); $("#SttlMerchId").text(result.SettlementMerchantId); $("#CreateDate").text(formatJSONDate(Date(result.AppendDts))); $("#ExpireDate").text(formatJSONDate(Date(result.ExpiresDts))); $("#LastUpdate").text(formatJSONDate(Date(result.LastUpdateDts))); $("#LastUpdatedBy").text(result.LastUpdateNt); $("#ProcessIn").text(result.ProcessIn); } ); return false; } function formatJSONDate(jsonDate){ var newDate = dateFormat(jsonDate, "mm/dd/yyyy"); return newDate; } This solution got my object from the callback method and displayed the dates on the page properly using the date format library.

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  • Track each URL and Parameters sent from Form

    - by Arjun
    Simple question really for anyone who's been through this: I have a form that I'm placing on a site. This form submits some parameters to a site which then sends some parameters using "GET" to another site, which then opens the third site. Now the first 2 sites pass so quickly that I can not see what parameters were passed using the URL. I can do a manual check using source code but its too long and complex. I just need a simple tool or hint or firefox addon on how to track every single URL (wven if it has a META redirect) so I can read parameters being sent via the form. Thanks

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  • efficient thread-safe singleton in C++

    - by user168715
    The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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  • Undefined Variable? But I defined it...

    - by Rob
    Well before anyone claims that theres a duplicate question... (I've noticed that people who can't answer the question tend to run and look for a duplicate, and then report it.) Here is the duplicate you are looking for: http://stackoverflow.com/questions/2481382/php-claims-my-defined-variable-is-undefined However, this isn't quite a duplicate. It gives me a solution, but I'm not really looking for this particular solution. Here is my problem: Notice: Undefined variable: custom Now here is my code: $headers = apache_request_headers(); // Request the visitor's headers. $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; //This is what the header should be. foreach ($headers as $header => $value) { $custom .= "$header: $value"; } Clearly, $custom is defined. According to the other question, it's a global and should be marked as one. But how is it a global? And how can I make it a (non-global)? The script works fine, it still displays what its supposed to and acts correctly, but when I turn on error messages, it simply outputs that notice as well. I suppose its not currently necessary to fix it, but I'd like to anyway, as well as know why its doing this.

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  • Attributes passed to .build() dont show up in the query

    - by Sebastian
    Hi there guys! Hope your all enjoying your hollydays. Ive run into a pretty funny problem when trying to insert rows into a really really simple database table. The basic idea is pretty simple. The user selects one/multiple users in a multiselect which are supposed to be added to a group. This piece of code will insert a row into the user_group_relationships table, but the users id always @group = Group.find(params[:group_id]) params[:newMember][:users].each do |uid| # For debugging purposes. puts 'Uid:'+uid @rel = @group.user_group_relationships.build( :user_id => uid.to_i ) @rel.save end The user id always gets inserted as null even though it is clearly there. You can see the uid in this example is 5, so it should work. Uid:5 ... SQL (0.3ms) INSERT INTO "user_group_relationships" ("created_at", "group_id", "updated_at", "user_id") VALUES ('2010-12-27 14:03:24.331303', 2, '2010-12-27 14:03:24.331303', NULL) Any ideas why this fails?

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  • In the generic programming/TMP world what exactly is a model / a policy and a "concept" ?

    - by Hassan Syed
    I'd like to know the precise yet succinct definitions of these three concepts in one place. The quality of the answer should depend on the following two points. Show a simple code snippet to show how and what the concept/technique is used for. Be simple enough to understand so that a programmer without any exposure to this area can grasp it. Note: There are probably many correct answers since each concept has many different facets. If there are a lot of good answers I will eventually turn the question into CW and aggregate the answers. -- Post Accept Edit -- Boost has a nice article on generic programming concepts

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  • How to enforce that HTTP client uses conditional requests for updates?

    - by Day
    In a (proper RMM level 3) RESTful HTTP API, I want to enforce the fact that clients should make conditional requests when updating resources, in order to avoid the lost update problem. What would be an appropriate response to return to clients that incorrectly attempt unconditional PUT requests? I note that the (abandoned?) mod_atom returns a 405 Method Not Allowed with an Allow header set to GET, HEAD (view source) when an unconditional update is attempted. This seems slightly misleading - to me this implies that PUT is never a valid method to attempt on the resource. Perhaps the response just needs to have an entity body explaining that If-Match or If-Unmodified-Since must be used to make the PUT request conditional in which case it would be allowed? Or perhaps a 400 Bad Request with a suitable explanation in the entity body would be a better solution? But again, this doesn't feel quite right because it's using a 400 response for a violation of application specific semantics when RFC 2616 says (my emphasis): The request could not be understood by the server due to malformed syntax. But than again, I think that using 400 Bad Request for application specific semantics is becoming a widely accepted pragmatic solution (citation needed!), and I'm just being overly pedantic.

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  • MySQL Returns wrong values on SELECT statement

    - by Andrew K
    All, I'm wondering if this is a MySQL bug, but since I've seen others playing with larger numbers than this, I'm thinking I'm doing something wrong here. Here is my table structure for the table I'm querying: mysql describe ipspace6\G ************* 1. row ************* Field: id Type: decimal(39,0) unsigned Null: NO Key: Default: NULL Extra: ************* 2. row ************* Field: addr Type: decimal(39,0) unsigned Null: NO Key: PRI Default: 0 Extra: ************* 3. row ************* Field: netmask Type: decimal(39,0) unsigned Null: NO Key: Default: 0 Extra: ************* 4. row ************* Field: subnet Type: int(4) Null: NO Key: Default: NULL Extra: Now, I run a simple SELECT statement against the "id" column: mysql SELECT id FROM ipspace6 WHERE id='50552019118453823914642686339427860480'; +----------------------------------------+ | id | +----------------------------------------+ | 50552019118453823730175245602332344320 | | 50552019118453823730175245602332344320 | | 50552019118453823914642686339427860480 | | 50552019118453823914642686339427860480 | +----------------------------------------+ ...What the heck is going on here? Two of these results are valid, and two definitely are not. It's not like I'm doing some super-complex nested query or anything, this is simple stuff, and it's driving me insane. Help, anyone?

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  • How To: Custom HTML / CSS Text Button for "Facebook like" & "Twitter Follow"

    - by 1Line
    So i have had a little hunt online about creating custom Facebook like buttons and custom twitter follow button but not really found a solution so thought i would ask here and see if anyone knows of a solution for this (currently i have coded some jQuery to get Facebook and Twitter counts using JSON which works but want some custom buttons as per below) I have the count working all ok, just need to tackle the like and follow buttons - it is done in jquery at the moment so would like to continue to use that if this has to be done via that. at the moment i use the API for each to get the count, if i can integrate into the current js i have to get the calls / functions i require would be good: // grab from facebook var facebook = $.getJSON('https://graph.facebook.com/'+f_page+'?callback=?', function(data) { fb_count = data['likes'].toString(); fb_count_gt = data['likes'].toString(); fb_count = add_commas(fb_count); $('#fb_count').html(fb_count); }); // grab from twitter var twitter = $.getJSON("https://twitter.com/users/"+t_page+".json?callback=?",function(data) { twit_count = data['followers_count'].toString(); twit_count_gt = data['followers_count'].toString(); twit_count = add_commas(twit_count); $('#twitter_count').html(twit_count); }); Thanks in advance!

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  • Where to start to create an HTML website with 2 tables read from csv files using anything but php

    - by CodingIsAwesome
    I want to design a website which displays on loading two tables each with it's respective data from a csv file. Then every minute the website automatically refreshes. This problem seems so simple! But yet the solution eludes me. All of the files will be contained in 1 directory, not on a server but on a local machine. Such as sitting on the desktop. I understand if I use javascript I have to use ADO, and I'm still trying to work out how to use ASP. I am new with both languages. So far the only restriction is that I can't use PHP. So the jist so far as I can think right now is: 1. read the file 2. place the file into an array by splitting at the commas 3. write the array into td's ????? 4. then print all this out into a div ???? I have googled my heart out and can't seem to find what I'm looking for. or even piece together what I'm looking for. Everything with javascript and ADO's leads me to dead ends, I can't find anything on ASP that is helpful. Could someone please write up some sample code for a resource? Or have a better solution?

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  • Rate my C# code (~300 SLOC) using GDI+/Backgroundworker

    - by sebastianlarsson
    Hi, I want to get some feedback on my code! Below is some background info. I am taking a pre-certification course in C# (Sweden, 15 ECTS). The focus of the course is theoretical and only limited practical work. I dont find the assignments very hard at all to tell you the truth, but since I only have very limited work experience as a developer (I have worked 15h/week at Ericsson since November) I think I would benefit from having the certificate (70-536 and more probably). I am currently reading Martin Fowler's "Refactoring: Improving the design of existing code" and I tried to apply his techniques to my latest lab in the course. I have been on the lookout for a website which have the idea of providing feedback on code, but so far I have yet to discover any. Please take a look on my code and tell me what you think. It is only roughly 300 lines of code divided into a couple of classes. GDI+, backgroundworker and user controls are what the lab is about. I reckon you may have to spend as little as a couple of minutes on looking on the solution. Link to solution: http://www.filefactory.com/file/b18h7d5/n/Lab4_Lab5_SebastianLarsson.zip Regards and thank you, Sebastian

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