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  • Return HTML from a user selection

    - by Cruinh
    I have the following, very simple html page... <html> <head> <script type="text/javascript"> function alertSelection() { var selection = window.getSelection(); var txt = selection.toString(); alert(txt); } </script> </head> <body> This is <span style="background-color:black;color:white">the</span> text. <div style="background-color:green;width:30px;height:30px;margin:30px" onmouseover="alertSelection()"> </body> </html> When I select the entire first line and mouseover the square, I get an alert with "This is the text.". How would I fix this so the the span tag or any other selected HTML isn't stripped out of the alert message?

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  • Can it be done?

    - by bzarah
    We are in design phase of a project whose goal is replatforming an ASP classic application to ASP.Net 4.0. The system needs to be entirely web based. There are several new requirements for the new system that make this a challenging project: The system needs to be database independent. It must, at version 1.0, support MS SQL Server, Oracle, MySQL, Postgres and DB2. The system must be able to allow easy reporting from the database by third party reporting packages. The system must allow an administrative end user to create their own tables in the database through the web based interface. The system must allow an administrative end user to design/configure a user interface (web based) where they can select tables and fields in the system (either our system's core tables or their own custom tables created in #3) The system must allow an administrative end user to create and maintain relationships between these custom created tables, and also between these tables and our system's core tables. The system must allow an administrative end user to create business rules that will enforce validation, show/hide UI elements, block certain actions based on the identity of specific users, specific user groups or privileges. Essentially it's a system that has some core ticket tracking functionality, but allows the end user to extend the interface, business rules and the database. Is this possible to build in a .Net, Web based environment? If so, what do you think the level of effort would be to get this done? We are currently a 6 person shop, with 2.5 full time developers.

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  • Checking Selected Radio Button after POST

    - by coffeeaddict
    I've been using ASP.NET controls which perform a lot of the manual for you. But I'm going back to the basics, what everyone else does. I'm using standard input tags. So for example if I have a radio button group and I select a button. When the form submits and does a POST back to whatever action="MyPage.aspx" then to grab and check the radio button's value that was selected is it always done like this below? <label><input type="radio" name="rbGroup" value='<%# ((Action)Container.DataItem).ID %>'/><%# ((Action)Container.DataItem).Name %></label> So here I'm appending the ID to the value. And then when it hits the page that my action specifies, I'm checking to see which was selected by trimming off and getting that ID from the value: string selection = Request.Form["rbGroup"]; string dbRecordIdSelected = int.Parse(selection.Substring(1)); so now I can check the id they selected...that is the ID of the db record that gave that selected radio it's name. Is that how you basically always check what radio was selected by checking the name/value pair that comes across for that selected radioButton group name? And then you can append stuff like IDs or whatever you want to grab and parse out to then do additional logic on the server-side once that header reaches the server and your specified page in the action attribute? The above code is not production code, just something to explain what I'm talking about.

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  • Hive performance increase

    - by Sagar Nikam
    I am dealing with a database (2.5 GB) having some tables only 40 row to some having 9 million rows data. when I am doing any query for large table it takes more time. I want results in less time small query on table which have 90 rows only-- hive> select count(*) from cidade; Time taken: 50.172 seconds hdfs-site.xml <configuration> <property> <name>dfs.replication</name> <value>3</value> <description>Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. </description> </property> <property> <name>dfs.block.size</name> <value>131072</value> <description>Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. </description> </property> </configuration> does these setting affects performance of hive? dfs.replication=3 dfs.block.size=131072 can i set it from hive prompt as hive>set dfs.replication=5 Is this value remains for a perticular session only ? or Is it better to change it in .xml file ?

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  • Git + SoA, one repo or many?

    - by parsenome
    Normally, when I start up a new application, I'd create a new git repository for it. That's well accepted and plays nice with Github when I want to share my code. At work, I'm working in a service oriented architecture. One very common pattern is to add some code to two different applications at the same time - perhaps adding a model with a RESTful interface to one and a web frontend for managing it on another. Using separate git repositories has some warts in this case. Here are what I see as the downsides of doing separate repositories: I have to commit twice I can't correllate related commits very well No single place to go back and trace history - I'd love to be able to bring up all my commits for the day in a single place Forgetting to pull one repo or another is a gotcha On the other hand, I've used perforce a lot and its one giant repository model has lots of warts too. Perforce has features designed to let help you with those, git doesn't. Has anyone else run into this situation? How did you handle it? What worked well, and what didn't?

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  • Need Help: adding MouseListeners to JComponents (Drawing a JComponent and then attaching a MouseListener)

    - by user1074574
    Drawing a JComponent and then attaching a MouseListener seems very simple to me, but not in this case: I'm having a problem with a MouseListener attached to a child JComponent; here's some brief code to help describe it: Note: The BGT class has implemented ActionListers/MouseListeners that do not have any code in them, and 'figures' is an array of SwingThings. public class GC extends BGT{ public GC(){ super(); buildJMenu(); drawPanel.addMouseListener(this); //drawPanel being the panel that draws the JComponents (it is a public variable in the BGT class) drawPanel.addMouseMotionListener(this); this.addMouseListener(this); } public static void main(String[] args){ GC a = new GC(); }... public void mouseClicked(MouseEvent e) { System.out.println(e.getSource()); //This only seems to print out the DrawPanel's information }... public void mouseReleased(MouseEvent e) { repaint(); ... tempMyJTextField = new MyJTextField(startX, startY, width, height); tempMyJTextField.addMouseListener(this); tempMyJTextField.addMouseMotionListener(this); figures.add(tempMyJTextField); for(int i = 0; i < figures.size(); i++) figures.get(i).addTo(drawPanel); } This is the addTo method in the MyJTextField class: public class MyJTextField extends JTextField implements SwingThing{ ... public void addTo(JPanel p) { p.add(myTextField); } ... } In the MouseClicked event it never registers that the JComponent was clicked. (The drawing/painting works fine) Thanks.

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  • Create an Oracle function that returns a table

    - by Craig
    I'm trying to create a function in package that returns a table. I hope to call the function once in the package, but be able to re-use its data mulitple times. While I know I create temp tables in Oracle, I was hoping to keep things DRY. So far, this is what I have: Header: CREATE OR REPLACE PACKAGE TEST AS TYPE MEASURE_RECORD IS RECORD ( L4_ID VARCHAR2(50), L6_ID VARCHAR2(50), L8_ID VARCHAR2(50), YEAR NUMBER, PERIOD NUMBER, VALUE NUMBER ); TYPE MEASURE_TABLE IS TABLE OF MEASURE_RECORD; FUNCTION GET_UPS( TIMESPAN_IN IN VARCHAR2 DEFAULT 'MONTLHY', STARTING_DATE_IN DATE, ENDING_DATE_IN DATE ) RETURN MEASURE_TABLE; END TEST; Body: CREATE OR REPLACE PACKAGE BODY TEST AS FUNCTION GET_UPS ( TIMESPAN_IN IN VARCHAR2 DEFAULT 'MONTLHY', STARTING_DATE_IN DATE, ENDING_DATE_IN DATE ) RETURN MEASURE_TABLE IS T MEASURE_TABLE; BEGIN SELECT ... INTO T FROM ... ; RETURN T; END GET_UPS; END TEST; The header compiles, the body does not. One error message is 'not enough values', which probably means that I should be selecting into the MEASURE_RECORD, rather than the MEASURE_TABLE. What am I missing?

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  • How can I achieve this kind of relationship (inheritance, composition, something else)?

    - by Tim
    I would like to set up a foundation of classes for an application, two of which are person and student. A person may or may not be a student and a student is always a person. The fact that a student “is a” person led me to try inheritance, but I can't see how to make it work in the case where I have a DAO that returns an instance of person and I then want to determine if that person is a student and call student related methods for it. class Person { private $_firstName; public function isStudent() { // figure out if this person is a student return true; // (or false) } } class Student extends Person { private $_gpa; public function getGpa() { // do something to retrieve this student's gpa return 4.0; // (or whatever it is) } } class SomeDaoThatReturnsPersonInstances { public function find() { return new Person(); } } $myPerson = SomeDaoThatReturnsPersonInstances::find(); if($myPerson->isStudent()) { echo 'My person\'s GPA is: ', $myPerson->getGpa(); } This obviously doesn't work, but what is the best way to achieve this effect? Composition doesn't sond right in my mind because a person does not “have a” student. I'm not looking for a solution necessarily but maybe just a term or phrase to search for. Since I'm not really sure what to call what I'm trying to do, I haven't had much luck. Thank you!

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  • Is Maven really flexible?

    - by Dima
    I understand how Maven works with .java files in src/java/main. But may it be used for a more general case? Let us put it more abstract: Suppose I already have some a.exe that read some (not necessarily only .java) sources from directories A1, A2, A3 and puts some files (maybe some are generated .java) to directories B1, B2. I also have some b.exe that currently reads files from B1, B2, B3 and generates something else. Some more similar steps. (A real life problem stands behind). I would like to right POM.xml file so that maven will do this work. Is that possible? I assume that a.exe and b.exe should be warped as maven plugings. Next, in Maven docs I see : <build> <sourceDirectory>${basedir}/src/main/java</sourceDirectory> <scriptSourceDirectory>${basedir}/src/main/scripts</scriptSourceDirectory> <testSourceDirectory>${basedir}/src/test/java</testSourceDirectory> <outputDirectory>${basedir}/target/classes</outputDirectory> <testOutputDirectory>${basedir}/target/test-classes</testOutputDirectory> ... </build> What bothers me is that "sourceDirectory" looks by itself as a hard coded name. Will Maven accept A1 and A2 tags instead?

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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  • MVC and binding to List of Checkboxes

    - by Josh
    Here is my problem. I have a list of models that are displayed to the user. On the left is a checkbox for each model to indicate that the user wants to choose this model (in this case, we're building products a user can add to their shopping cart). The model has no concept of being chosen...it strictly has information about the product in question. I've talked with a few other developers after having gone through and the best I could come up with is getting the formcollection and string parsing the key values to determine whether the checkbox is checked or not. This doesn't seem ideal. I was thinking there would be something more strongly bound, but I can't figure out a way to do it. I tried creating another model that had a boolean property to represent being checked and a property of the model and passing a list of that model type to the view and creating a ActionResult on the controller that accepts a list of the new model / checked property, but it comes back null. Am I just thinking too much like web forms and should just continue on with parsing checkbox values? Here's what I've done for wrapping the models inside a collection: public class SelectableCollection[T] : IList[T] {} public class SelectableTrack{ public bool IsChecked{get;set;} public bool CurrentTrack{get;set;} } For the view, I inherit from ViewPage[SelectableCollection[SelectableTrack]] For the controller, I have this as the ActionResult: [HttpPost] public ActionResult SelectTracks(SelectableCollection sc) { return new EmptyResult(); } But when I break inside the ActionResult, the collection is null. Any reason why it isn't coming through?

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  • C# properties: How are they instantiated?

    - by Pedery
    Hi! This might be a pretty straightforward question, but I'm trying to understand some of the internal workings of the compilation. Very simply put, imagine an arbitrary object being instantiated. This object is then allocated on the heap. The object has a property of type PointF (which is value type), with a get and a set method. Imagine the get and the set method containing a few calculations for doing their work. How and where (stack/heap) and when is this code instantiated? This is the background for this question: I'm writing get and set methods for an object and these methods need to be accessed very frequently. The get and set code in itself is rather massive so I feared that in a worst case scenario the methods would be instantiated as an object or a value type with all internal code for every access of the property. On the other hand the code is probably instantiated when the main object is created and the CPU is simply told to jmp to the property code start. Anyway, this is what I want to have clarified.

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  • problem during data fetch

    - by nectar
    here is my code $sql="SELECT * FROM $tbl_name WHERE ownerId='$UserId'"; $result=mysql_query($sql,$link)or die(mysql_error()); $row = mysql_fetch_array($result, MYSQL_ASSOC); <?php while($row = mysql_fetch_array($result, MYSQL_ASSOC)) { echo "<tr>"; echo "<td>".$row['pinId']."</td>"; echo "<td>".$row['usedby']."</td>"; echo "<td>".$row['status']."</td>"; echo "</tr>"; } ?> it is ignoring the first record means if 4 rows are in $row its ignoring the 1st one rest three are coming on page. ownerId is not primary key.

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  • OpenCalais API using jQuery

    - by Varun
    Hi I've wanted to do some language processing for an application and have been trying to use the OpenCalais API. The call to the API works perfectly and returns data. The problem is that even though I can see the data in the firebug, I cannot access it because the callback never triggers. Details: the call requires callback=? as it is a JSONP request. so callback=foo SHOULD call the foo method once the data is returned, it doesn't. in fact, if callback is anything other than ? the call fails and doesn't return any data. (i've also checked JSLint to make sure the returned JSON is valid). tried using $.ajax instead of $.getJSON so that I can get an error callback, but neither the success or error callbacks fire. in firebug, usually when you make a JSON request, the request shows up in the console. In this case, the request doesn't show up in the console, but instead shows in the "Net" tab in firebug...dunno what that means, but somehow the browser doesn't think its an XHR request. any ideas? thanks.

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  • Invoking [SKProductsRequest start] hangs on iOS 4.0

    - by figelwump
    Encountering an issue with SKProductsRequest that is specific to iOS 4.0. The problematic code: - (void)requestProductData { NSSet *productIdentifiers = [NSSet setWithObjects:kLimitedDaysUpgradeProductId, kUnlimitedUpgradeProductId, nil]; self.productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:productIdentifiers]; self.productsRequest.delegate = self; [self.productsRequest start]; } - (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response { NSLog(@"didReceiveResponse"); } When [SKProductsRequest start] is invoked, the productsRequest:didReceiveResponse: delegate method is never invoked; further, the entire app hangs and is completely unresponsive to input. Obviously, this is a huge issue for our iOS 4.0 users as it not only breaks payments but makes the app completely unusable. Some other things to note: this only happens on iOS 4.0; iOS 4.2, 3.x are fine. Also: if the delegate is not set on the SKProductsRequest (i.e. comment out the line "self.productsRequest.delegate = self;"), the app doesn't hang (but of course in that case we have no way of getting the product info). Also, the problem still reproduces with everything stripped out of the productsRequest:didReceiveResponse: callback (that method never actually gets called). Finally, if the productIdentifiers NSSet object is initialized to an empty set, the hang doesn't occur. Has anybody else experienced this? Any ideas/thoughts on what could be going on here, and how we might be able to work around this?

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  • Coloring Default Buttons - color filter only on unfocused state

    - by rlo
    I want to buttons of different colors, but I want to do so while using the default button background resource in order to preserve the onfocus and onclick states. This is because I want to use the default highlight color of the OS for my app, which is NOT always orange (HTC Sense makes it green). I found that adding a color filter to the button's background drawable works great (in this case, blue): myButton.getBackground().setColorFilter(Color.parseColor(this.getString (R.color.button_blue)), Mode.MULTIPLY); BUT, when the button is focused or clicked, it turns a nasty orange_blue because it mixes the color filter with the orange of the background drawable. I want to ONLY set this color filter for the unfocused/unclicked nine- patch drawable within the default button's statelistdrawable. I'm not sure how else to do this. I see a similar solution here: http://stackoverflow.com/questions/2065430/fixed-android-detecting-fo... but I have some concerns with that solution, mainly what if the OS changes the graphic of the default button? Since the normal unfocused/ unpressed graphic is now hardcoded into the app, it would break the flow. Maybe can someone comment on whether it would be good or bad practice to hardcode the default graphic into the app? What are the chances of the OS completely changing the graphic? Any help please? Thanks very much!!

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  • How to use project which is already in VSS?

    - by shekhar
    Hi, I am trying to add my project under source control. I am using "Microsoft VSS 6.0" for it. My problem is, there is one project in VSS which I had copied on my system using 'Get Latest Version' to C:\latest_version directory. Then I copied that entire project in other directory (C:\working) and deleted the directory where I had taken latest version of it (C:\latest_version). Now everytime I make any changes in code and want to do check in, I need to check out that particular file in some folder, copy-replace that file with my new file and check-in. Can we do all this through visual studio? I saw some tutorials which describe how to add project to VSS but in my case project is already is in VSS and I just want to link it with my project. Is it possible? I dont know whether I am using VSS correctly or not. I would like to know how do people usually use it? How to do check-in , check-out? Thanks in advance !!

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  • getting double value from group concact

    - by Sackling
    I am having a problem where I am getting duplicated values from what I think I should be getting. here is my sql: SELECT DISTINCT p.products_image, pd.products_name, p.products_id, p.products_model, p.manufacturers_id, m.manufacturers_name, p.products_price, p.products_sort_order, p.products_tax_class_id, pd.products_viewed, group_concat(p2i.icons_id separator ",") AS icon_ids, group_concat(pi.icon_class separator ",") AS icon_class, IF(s.status, s.specials_new_products_price, NULL) AS specials_new_products_price, IF(s.status, s.specials_new_products_price, p.products_price) AS final_price FROM products p LEFT JOIN specials s ON p.products_id = s.products_id LEFT JOIN manufacturers m ON p.manufacturers_id = m.manufacturers_id JOIN products_description pd ON p.products_id = pd.products_id JOIN products_to_categories p2c ON p.products_id = p2c.products_id INNER JOIN products_specifications ps7 ON p.products_id = ps7.products_id LEFT JOIN products_to_icon p2i ON p.products_id = p2i.products_id LEFT JOIN products_icons pi ON p2i.icons_id = pi.icons_id WHERE p.products_status = '1' AND pd.language_id = '1' AND ps7.specification IN ('Polycotton' , 'Reflective') AND ps7.specifications_id = '7' AND ps7.language_id = '1' AND p2c.categories_id = '21' GROUP BY p.products_id ORDER BY p.products_sort_order The column that is getting double values is icon_ids from the group concact. This seams to happen only if ploycotton, and reflective are both IN ps7.specification. If it is only one or the other then it works fine. The products_to_icon table contains 2 columns, products_id and icons_id. If a product has 2 icons, there are 2 rows so I'm pretty sure it is this fact that is causing the duplicate icons ids. When I run this, the icon_ids column for a product with 2 icons is "4,4,6,6" for example, when what I need is "4,6"

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  • Name lookup for names not dependent on template parameter in VC++2008 Express. Is it a bug?

    - by Maciej H
    While experimenting a bit with C++ templates I managed to produce this simple code, for which the output is different, than I expected according to my understanding of C++ rules. void bar(double d) { std::cout << "bar(double) function called" << std::endl; } template <typename T> void foo(T t) { bar(3); } void bar(int i) { std::cout << "bar(int) function called" << std::endl; } int main() { foo(3); return 0; } When I compile this code is VC++2008 Express function bar(int) gets called. That would be the behaviour I would expect if bar(3);in the template body was dependent on the template parameter. But it's not. The rule I found here says "The C++ standard prescribes that all names that are not dependent on template parameters are bound to their present definitions when parsing a template function or class". Am I wrong, that "present definition" of bar when parsing the template function foo is the definition of void bar(double d);? Why it's not the case if I am wrong. There are no forward declarations of bar in this compilation unit.

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  • has_many :through default values

    - by David Lyod
    I have a need to design a system to track users memberships to groups with varying roles (currently three). class Group < ActiveRecord::Base has_many :memberships has_many :users, :through => :memberships end class Role < ActiveRecord::Base has_many :memberships has_many :users, :through => :memberships end class Membership < ActiveRecord::Base belongs_to :user belongs_to :role belongs_to :group end class User < ActiveRecord::Base has_many :memberships has_many :groups, :through => :memberships end Ideally what I want is to simply set @group.users << @user and have the membership have the correct role. I can use :conditions to select data that has been manually inserted as such : :conditions => ["memberships.grouprole_id= ? ", Grouprole.find_by_name('user')] But when creating the membership to the group the grouprole_id is not being set. Is there a way to do this as at present I have a somewhat repetitive piece of code for each user role in my Group model.

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  • Apprequest Dialog stopped working (FB-AS3 API)

    - by warran
    I'm writing ActionScript game and wanted to integrate it with FB, so I used http://code.google.com/p/facebook-actionscript-api/ with custom dialog function I've found in same issue thread. It goes like this: protected function dialog(method:String, callback:Function, stageReference:Stage, stageWebView:StageWebView, params:* = null):void { dialogCallback = callback; stageRef = stageReference; webView = stageWebView; webView.stage = stageReference; webView.assignFocus(); dialogWindow = new DialogWindow(handleDialog); dialogWindow.open(method, applicationId, webView, params); } I've written module to handle all the FB stuff and it worked perfectly. But few days ago I've noticed that dialog shows up, but when I select friends and try to send apprequest to them i get error: An error occurred with your app. Please try again later. API Error Code: 2 API Error Description: Service temporarily unavailable Error Message: User can't send this request: Unknown error I've checked it, and found out, that after selecting friends and clicking send dialog changes location to http://www.facebook.com/dialog/apprequest, the error occures, and than after clicking "ok" it changes location to redirect_uri. Do you have any ideas? Is this my fault or facebooks'?

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  • Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

    - by DanM
    I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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  • EF4 querying through the generations

    - by Hans Kesting
    I have a model withs Parents, Children and Grandchildren, in a many-to-many relationship. Using this article I created POCO classes that work fine, except for one thing I can't yet figure out. When I query the Parents or Children directly using LINQ, the SQL reflects the LINQ query (a .Count() executes a COUNT in the database and so on) - fine. The Parent class has a Children property, to access it's children. But (and now for the problem) this doesn't expose an IQueryable interface but an ICollection. So when I access the Children property on a particular parent all the Parent's Children are read. Even worse, when I access the Grandchildren (theParent.Children.SelectMany(child => child.GrandChildren).Count()) then for each and every child a separate request is issued to select it's grandchildren. Changing the type of the Children property from ICollection to IQueryable doesn't solve this. Apart from missing needed methods like Add() and Remove(), EF just doesn't recognize the property then. Are there correct ways (as in: low database interaction) of querying through children (and what are they)? Or is this just not possible?

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  • Using data.table to aggregate

    - by dayne
    After multiple suggestions from SO users, I am finally trying to convert my code over to using data.tables. library(data.table) DT <- data.table(plate = paste0("plate",rep(1:2,each=5)), id = rep(c("CTRL","CTRL","ID1","ID2","ID3"),2), val = 1:10) > DT plate id val 1: plate1 CTRL 1 2: plate1 CTRL 2 3: plate1 ID1 3 4: plate1 ID2 4 5: plate1 ID3 5 6: plate2 CTRL 6 7: plate2 CTRL 7 8: plate2 ID1 8 9: plate2 ID2 9 10: plate2 ID3 10 What I would like to do is take the average of DT[,val] by plate when the id is "CTRL". I would normally aggregate the data frame, then use match to map the values back to a new column, 'ctrl'. Using the data.table package I can get: DT[id=="CTRL",ctrl:=mean(val),by=plate] > DT plate id val ctrl 1: plate1 CTRL 1 1.5 2: plate1 CTRL 2 1.5 3: plate1 ID1 3 NA 4: plate1 ID2 4 NA 5: plate1 ID3 5 NA 6: plate2 CTRL 6 6.5 7: plate2 CTRL 7 6.5 8: plate2 ID1 8 NA 9: plate2 ID2 9 NA 10: plate2 ID3 10 NA What I need is really: DT <- data.table(plate = paste0("plate",rep(1:2,each=5)), id = rep(c("CTRL","CTRL","ID1","ID2","ID3"),2), val = 1:10, ctrl = rep(c(1.5,6.5),each=5)) > DT plate id val ctrl 1: plate1 CTRL 1 1.5 2: plate1 CTRL 2 1.5 3: plate1 ID1 3 1.5 4: plate1 ID2 4 1.5 5: plate1 ID3 5 1.5 6: plate2 CTRL 6 6.5 7: plate2 CTRL 7 6.5 8: plate2 ID1 8 6.5 9: plate2 ID2 9 6.5 10: plate2 ID3 10 6.5 Eventually I would like to use much more complicated selections of the values, but I do not know how to select specific values, run some function, then map those values back to the appropriate row using data frames.

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