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• Can you explain what's going on in this Ruby code?

  - by samoz

  I'm trying to learn Ruby as well as Ruby on Rails right now. I'm following along with Learning Rails, 1st edition, but I'm having a hard time understanding some of the code. I generally do work in C, C++, or Java, so Ruby is a pretty big change for me. I'm currently stumped with the following block of code for a database migrator: def self.up create_table :entries do |t| t.string :name t.timestamps end end Where is the t variable coming from? What does it actually represent? Is it sort of like the 'i' in a for(i=0;i<5;i++) statement? Also, where is the :entries being defined at? (entries is the name of my controller, but how does this function know about that?)

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• The Elegant way to handle Cyclic Event in Java ??

  - by dex

  Hi fellows, i think this not a specific problem to me; everybody might have encountered this issue before. To properly illustrate it, here's a simple UI: As you can see, those two spinners are controlling a single variable -- "A". The only difference is that they control it using different views. If i change the top spinner, "A" will be changed and the bottom spinner's value will also be updated accordingly. However, updating the bottom spinner's call (such as setValue) will also trigger another event instructing the top spinner to update based on the bottom spinner's value. Thus creates a bad cycle which can eventually cause a StackOverFlow exception. My previously solution is kinda cumbersome: i placed a guarding boolean to indicate whether the 2nd updating call should be performed. Now i'd like to ask "how can i handle such situation elegantly?" thx

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• How to replace the nth column/field in a comma-separated string using sed/awk?

  - by Peter Meier

  assume I have a string "1,2,3,4" Now I want to replace, e.g. the 3rd field of the string by some different value. "1,2,NEW,4" I managed to do this with the following command: echo "1,2,3,4" | awk -F, -v OFS=, '{$3="NEW"; print }' Now the index for the column to be replaced should be passed as a variable. So in this case index=3 How can I pass this to awk? Because this won't work: echo "1,2,3,4" | awk -F, -v OFS=, '{$index="NEW"; print }' echo "1,2,3,4" | awk -F, -v OFS=, '{$($index)="NEW"; print }' echo "1,2,3,4" | awk -F, -v OFS=, '{\$$index="NEW"; print }' Thanks for your help!

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• FOR XML PATH Query results to file with SSIS

  - by whimsql

  In SSMS I've gotten my for xml path query written and it's beautiful. I put it in an "Execute SQL Task" in the Control Flow, set the resultset to XML. Now how to I get the results into an actual xml file that I can turn around and FTP to a third party? This should have been so easy! I would put the XML into a variable but we are looking at a HUGE file, possibly 100mb+ Do I need to use a Script Task? (I'd like to avoid that if there is another option.)

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• Screening (multi)collinearity in a regression model

  - by aL3xa

  I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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• Flex 4.6 Mobile - Scrolling to the last added item in a dataGrid with variableRowHeight

  - by user1305331

  I'm trying to set the scroll vertical position of a spark dataGrid to show the items as I add them to the grid. I know you can set the scroll position like this: dataGrid.scroller.viewport.verticalScrollPosition = itemPosition*rowHeight; The problem is that the dataGrid have variableRowHeight, as each row word wraps their name labels, and I don't know how to get each row height. I though of getting the itemRenderer associated with every item as I add it to the grid, and keep the total row height value in a variable, but don't know how to achieve that. Is there any way to set the scroll position of a dataGrid with variableRowHeight to show the last added item?

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• Show UIView for app presentation only once in iOS

  - by André Muniz

  I need to show an UIScrollView with some pages for present the app to user when launched for the first time. My slides are working correctly, lefting the logic to present it. Is a good practice to set the UIScrollViewController as root controller and set a NSUserDefault variable to control the presentation and redirect to main controller or set the main ViewController as root normally and call the presentation view if needed is a better approach? If there is a better way to do this can someone help? Thanks.

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• const read only local copies

  - by robUK

  Hello gcc 4.4.4 c89 I am just wondering is it worth passing a const into a function. i.e. void do_something(const char *dest, const int size) The size is a read-only so I don't want to change it. However, some developers never have this as const has it is a local copy that is being used. The pointer is const as you can change the value in the calling routine. I always have a const on read-only local copies, as it confirms to anyone reading my code that it is a read-only variable. And also, when coding I don't make the mistake of changing it without realizing. Many thanks for any suggestions,

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• Using javascript on an HTML table?

  - by Michael McKay

  Hi, few questions, just wondering if anyone can help? I have a table with 1 long row (1000 pixels) and one single column, how do i go about creating a method whereby when the mouse cursor is on the leftmost side of the cell, a variable, lets say X is set to 0, the further right the mouse cursor moves in the cell, the value of X increases. I know that sounds like a strange question but im working on a project where this type of functionality is desired. Is there a javascript method to create this feature? Thanks for any help.

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• How are exceptions allocated on the stack caught beyond their scope?

  - by John Doe

  In the following code, the stack-based variable 'ex' is thrown and caught in a function beyond the scope in which ex was declared. This seems a bit strange to me, since (AFAIK) stack-based variables cannot be used outside the scope in which they were declared (the stack is unwound). void f() { SomeKindOfException ex(...); throw ex; } void g() { try { f(); } catch (SomeKindOfException& ex) { //Handling code... } } I've added a print statement to SomeKindOfException's destructor and it shows that ex is destructed once it goes out of scope in f() but then it's caught in g() and destructed again once it goes out of scope there as well. Any help?

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• jquery - Create a List of all LIs Name's

  - by nobosh

  Given the following block of HTML: <ul id="taglist"> <li><a name="45" href="">Product 1</a></li> <li><a name="1146" href="">Product 2</a></li> <li><a name="13437" href="">Product 3</a></li> <li><a name="51" href="">Product 4</a></li> </ul> Is it possible for JQUERY to return a STRING, one variable with the name values: alert(tagliststring); Would alert: 45,1146,13437,51 Thanks

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• Copy and Store LPTSTR in class causes crash

  - by Jake M

  I am attempting to copy a LPTSTR and store that string as a member variable in an object. But my attempts to copy the LPTSTR seem to fail and when I go to access/print the value of the copied LPTSTR I get a program crash. Is it possible to copy a LPTSTR and store it in my class below or is it better to just use a TCHAR*? class Checkbox { private: LPTSTR text; HWND hwnd; public: Checkbox(HWND nHwnd, LPTSTR nText) { lstrcpy(checkText, text); } void print() { // Causes a crash MessageBox(hwnd, text, text, MB_OK); } };

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• Using Jquery $getJSON How do I dynamically create data for the [data] parameter after Url param?

  - by Breadtruck

  I have no problems getting the Json to work and parse the json return. I was just wondering how I could build a dynamic "whatever data is" and stick it into [data] to pass my parameters from there and not manually append them to the url. From jquery website example: $.getJSON("test.js", { name: "John", time: "2pm" }, function(json){ alert("JSON Data: " + json.users[3].name); }); I thought I could build a string ( which doesn't make sense anyway ) and drop it inside the { }, but I obviously don't understand that part. name: isn't a string and you can't put a variable in that part, so how would I dynamically put items into whatever [data] is.

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• How Pick a Column Value from a ListView Row - C#.NET

  - by peace

  How can i fetch the value 500 to a variable from the selected row? One solution would be to get the row position number and then the CustomerID position number. Can you please give a simple solution. SelectedItems means selected row and SubItems means the column values, so SelectedItem 0 and SubItem 0 would represent the value 500. Right? This is how i populate the listview: for (int i = 0; i < tempTable.Rows.Count; i++) { DataRow row = tempTable.Rows[i]; ListViewItem lvi = new ListViewItem(row["customerID"].ToString()); lvi.SubItems.Add(row["companyName"].ToString()); lvi.SubItems.Add(row["firstName"].ToString()); lvi.SubItems.Add(row["lastName"].ToString()); lstvRecordsCus.Items.Add(lvi); }

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• declaring a 2D array of pointer objects

  - by Tyler Stennette

  I'm having a tough time figuring out how to instantiate a 2D array of pointer objects. Here is how I'm doing it: Pieces* chessBoard[9][9]; When I want to set it to an actual object pointer, I'm doing the following: chessBoard[1][1] = new Rook(p1Rook); Rook is a class that inherits attributes from the Pieces class and p1Rook is a char variable set to 'R'. This class also implements virtual functions (not pure virtual) from Pieces such as move() or getPiece() that are unique to the particular chess piece. However, when I compile my program, I get the following error: ChessBoard.cpp:69: error: expected type-specifier before ‘Rook’ ChessBoard.cpp:69: error: cannot convert ‘int*’ to ‘Pieces*’ in assignment Can someone please explain what I should change to get rid of this rather annoying persistent error? I would appreciate it.

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• Best method to cleanly shut down an application launched via another.

  - by JYelton

  I couldn't find any close answers to this, so I'm consulting the experience of SO users: Scenario: I have two small C# winforms applications where one behaves as a server or host, the other as a client. They share data via SQL Server, in terms of configuration settings. I am currently launching the client application (which only needs to run periodically) from the server application via Process.Start() and terminating it via Process.CloseMainWindow() (after finding it in the process list). While it seems clean enough, I wondered if there's a better way. Question: Which way would be best to instruct the client application to shut down: Continue using Process.CloseMainWindow()? Implement WCF between the applications? (I would need help on how to do this.) Set a variable in SQL that the client application checks for? Some other way?

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• Opening Large (24 GB) File In C

  - by zacaj

  I'm trying to read in a 24 GB XML file in C, but it won't work. I'm printing out the current position using ftell() as I read it in, but once it gets to a big enough number, it goes back to a small number and starts over, never even getting 20% through the file. I assume this is a problem with the range of the variable that's used to store the position (long), which can go up to about 4,000,000,000 according to http://msdn.microsoft.com/en-us/library/s3f49ktz%28VS.80%29.aspx, while my file is 25,000,000,000 bytes in size. A long long should work, but how would I change what my compiler(Cygwin/mingw32) uses or get it to have fopen64?

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• Cursors vs Procedures in SQL

  - by CogitoErgoSum

  So, I just learned about CURSORS but still don't exactly grasp them. What is the difference between a cursor and procedure or even a function? So far from the various examples (DECLARE CURSOR ... SELECT ... FROM ...) It seems at most its a variable to hold a query. Is the data real time, or a snapshot of when the cursor was declared? i.e. I have a table with one row and one col with a value of 2. I do DECLARE CURSOR ... SELECT * FROM table1 I then insert a new row with a value of 3. When I run the cursor, would I Just get the one row from before the cursor was declared, or both rows? Thanks

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• setting actionscript 3 superclass variables

  - by jedierikb

  In AS3, if I have a class such: public class dude { //default value for a dude protected var _strength:Number = 1; public function dude( ):void { super( ); //todo... calculate abilities of a dude based on his strength. } } and a subclass public class superDude extends dude { public function superDude( ):void { _strength = 100; super( ); trace( "strength of superDude: " + _strength ); } } This will trace strength of superDude is 1. I expected the variable I set in the subclass (prior to calling the superclass constructor) to remain. Is there a way to assign class variables in subclass constructors which are not over-written by the superclass construtor? Or should I pass them up as constructor variables?

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• converting string to int in C++

  - by xbonez

  I am trying to convert a string I read in from a file to an int value so I can store it in an integer variable. This is what my code looks like: ifstream sin; sin.open("movie_output.txt"); string line; getline(sin,line); myMovie.setYear(atoi(line)); Over here, setYear is a mutator in the Movie class (myMovie is an object of Movie class) that looks like this: void Movie::setYear(unsigned int year) { year_ = year; } When I run the code, I get the following error: error C2664: 'atoi' : cannot convert parameter 1 from 'std::string' to 'const char *' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

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• PagedDataSource does not support serialization - how can I enforce this ?

  - by Darkyo

  Sounds like I want to override a physics law, but at least it is the most reasonnable solution, cpu / HDD and Ram effective for my asp.net project. In fact, I got a pageddataSource and a customDataReader that supports paginated data. The truth is my data are in a viewstate variable, because it is re-used in an update panel. When I intend to use it into my pageddatasource, asp.net 3.5 kills me with a System.Web.UI.WebControls.PagedDataSource' in Assembly 'System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable. cool exception... So I'd rather not offend newton because I know he'll always win, but I would need some help to enforce this pagedDataSource law, that seems so unbelievable, except if someone has an explanation.

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• View a SYS.XMLTYPE returned from an Oracle function, using PL/SQL

  - by caerphilly

  I have an Oracle function that dynamically creates an XML document, and returns it in a SYS.XMLTYPE value. I want to run a query from SQL Developer that calls that function and prints the document (either via a select, or dbms_output - I don't care). But all the examples/documentation seem to refer to querying XML columns in tables, and I can't seem to get the syntax right for my particular usage. I'd like something like this: declare x SYS.XMLTYPE; begin x := my_package.my_function(); select x.getclobval() from x; -- doesn't work! end; How can I print out the value of the XML type variable 'x' in the above code?

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• Adding List Array item In A Data Table Using Loop Results Error .. .

  - by Syed Raza

  I am trying to put the list array(res) item in to the Data Table(_Hdt) using for Loop I have put the values in "res" list erray using loop...but this loop results in an error: "variable use asd a method ?" Here _Hdt and dt are data table and res is list array, for (int r = 0; r < _Hdt.Rows.Count; r++) { foreach (DataRow row in dt.Select("DATE='" + _Hdt.Rows[r]["DATE"].ToString().Trim() + "'")) { DateTime date = Convert.ToDateTime(_Hdt.Rows[r]["DATE"].ToString().Trim()); string dateformat = String.Format("{0:dddd MMM d}", date); _Hdt.Rows[r]["DATE"] = dateformat; _Hdt.Rows[r]["MTU"] = row["MTU"].ToString().Trim(); _Hdt.Rows[r]["POWER"] = (Convert.ToDecimal(row["POWER"].ToString().Trim()) / 1000).ToString(); _Hdt.Rows[r]["COST"] = row["COST"].ToString().Trim(); _Hdt.Rows[r]["VOLTAGE"] = row["VOLTAGE"].ToString().Trim(); _Hdt.Rows[r]["KW"] = res(r); } }

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• Creating a Cocoa Framework

  - by David Schiefer

  Hi, I've created a working Cocoa framework which I wish to redistribute. The problem is however, it won't run outside of Xcode. I've read something about @executable_path/../Frameworks, which I did not include, because I don't know where to put it :/ Therefore I run my app in Xcode using the DYLD_FRAMEWORK_PATH variable which works fine, but only in Xcode - if I try to run it on its own it crashes straight away and says IMAGE NOT FOUND. I'm sure @executable_path/../Frameworks is what's missing, but I don't know where to put it. Could anyone help me out please? :) Thanks

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• Problem with debug watch in Visual Studio with yield return enumerator methods

  - by Stuart

  I have a method which returns an IEnumerable<> which it builds up using the yield return syntax: public IEnumerable<ValidationError> Validate(User user) { if (String.IsNullOrEmpty(user.Name)) { yield return new ValidationError("Name", ValidationErrorType.Required); } [...] yield break; } If I put a breakpoint in the method, I can step over each line, but if I try to use the Watch or Immediate windows to view the value of a variable I get this error: Cannot access a non-static member of outer type '[class name].Validate' via nested type '[class name]' Does anyone know why this is and how I can get around it?

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