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• Which Java Service or Daemon framework would you recommend?

  - by blwy10

  I have encountered many different ways to turn a Java program into a Windows Service or a *nix daemon, such as Java Service Wrapper, Apache Commons Daemon, and so on. Barring licensing concerns (such as JSW's GPL or pay dual-license), and more advanced features, which one would you recommend? All I intend to do is convert a simple Java program into a service; I don't need anything fancy, just something that runs as a service or a daemon, so I can start it or stop it in the service manager, or it runs for the lifetime of my *nix uptime. EDIT: I've decided to make this community wiki. I didn't start this question with an intention to find an answer for a problem I really had. I was just doing some reading and researching and chanced upon this question, so I was looking for recommendations and the like. Sorry for not doing this sooner or doing this at first. I didn't know what community wiki was for when I first started, and I completely forgot about this question until now. Many thanks for the answers!

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• Should xml represent a set or a list?

  - by sixtyfootersdude

  I always think of xml like a set data structure. Ie: <class> <person>john</person> <person>sarah</person> </class> Is equivalent to: <class> <person>sarah</person> <person>john</person> </class> Question One: Are these two things logicly equivalant? Are you allowed to make things like this in xml? <methodCall> <param>happy</param> <param>sad</param> </methodCall> Or do you need to do it like this: <methodCall> <param arg="1">happy</param> <param arg="2">sad</param> </methodCall> Question Two: Are these two things logically equivalent? Question Three: Is xml usually treated like a set or a list?

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• C++ Macro Arithmetric

  - by anon

  I have to do with Macros (it's macros calling macros; so templates are out of the question). Here's what I want: foo(3, a, b1, c1) --> foo1(a, b1, c1); foo(5, a, b1, c1, b2, c2) -> foo2(a, b1, c1, b2, c2); foo(7, a, b1, c1, b2, c2, b3, c3) -> foo3(a, b1, c1, b2, c2, b3, c3); So basically, what I want is to be able to execute the "function" n - (n-1)/2 at macro expansion time. Is this possible? Thanks! [PS, if you dislike my questions; I support your right to downvote; my worst question so far is only -17, so maybe we can break that record; however, please let me know why my question is technically invalid.] Thanks EDIT: Foo takes a variable # of arguments, of the form: foo(N, a1, b1, a2, b2, ... a_N, b_N) -> foo##N(a1, b1, a2, b2, ... a_N, b_N);

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• In Ruby, why is a method invocation not able to be treated as a unit when "do" and "end" is used?

  - by Jian Lin

  The following question is related to the question "Ruby Print Inject Do Syntax". My question is, can we insist on using do and end and make it work with puts or p? This works: a = [1,2,3,4] b = a.inject do |sum, x| sum + x end puts b # prints out 10 so, is it correct to say, inject is an instance method of the Array object, and this instance method takes a block of code, and then returns a number. If so, then it should be no different from calling a function or method and getting back a return value: b = foo(3) puts b or b = circle.getRadius() puts b In the above two cases, we can directly say puts foo(3) puts circle.getRadius() so, there is no way to make it work directly by using the following 2 ways: a = [1,2,3,4] puts a.inject do |sum, x| sum + x end but it gives ch01q2.rb:7:in `inject': no block given (LocalJumpError) from ch01q2.rb:4:in `each' from ch01q2.rb:4:in `inject' from ch01q2.rb:4 grouping the method call using ( ) doesn't work either: a = [1,2,3,4] puts (a.inject do |sum, x| sum + x end) and this gives: ch01q3.rb:4: syntax error, unexpected kDO_BLOCK, expecting ')' puts (a.inject do |sum, x| ^ ch01q3.rb:4: syntax error, unexpected '|', expecting '=' puts (a.inject do |sum, x| ^ ch01q3.rb:6: syntax error, unexpected kEND, expecting $end end) ^ finally, the following version works: a = [1,2,3,4] puts a.inject { |sum, x| sum + x } but why doesn't the grouping of the method invocation using ( ) work in the earlier example? What if a programmer insist that he uses do and end, can it be made to work?

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• Using classes for the first time,help in debugging

  - by kaushik

  here is post my code:this is no the entire code but enough to explain my doubt.please discard any code line which u find irrelavent enter code here saving_tree={} isLeaf=False class tree: global saving_tree rootNode=None lispTree=None def __init__(self,x): file=x string=file.readlines() #print string self.lispTree=S_expression(string) self.rootNode=BinaryDecisionNode(0,'Root',self.lispTree) class BinaryDecisionNode: global saving_tree def __init__(self,ind,name,lispTree,parent=None): self.parent=parent nodes=lispTree.getNodes(ind) print nodes self.isLeaf=(nodes[0]==1) nodes=nodes[1]#Nodes are stored self.name=name self.children=[] if self.isLeaf: #Leaf Node print nodes #Set the leaf data self.attribute=nodes print "LeafNode is ",nodes else: #Set the question self.attribute=lispTree.getString(nodes[0]) self.attribute=self.attribute.split() print "Question: ",self.attribute,self.name tree={} tree={str(self.name):self.attribute} saving_tree=tree #Add the children for i in range(1,len(nodes)):#Since node 0 is a question # print "Adding child ",nodes[i]," who has ",len(nodes)-1," siblings" self.children.append(BinaryDecisionNode(nodes[i],self.name+str(i),lispTree,self)) print saving_tree i wanted to save some data in saving_tree{},which i have declared previously and want to use that saving tree in the another function outside the class.when i asked to print saving_tree it printing but,only for that instance.i want the saving_tree{} to have the data to store data of all instance and access it outside. when i asked for print saving_tree outside the class it prints empty{}.. please tell me the required modification to get my required output and use saving_tree{} outside the class..

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• Core Data Errors vs Exceptions Part 3

  - by John Gallagher

  My question is similar to this one. Background I'm creating a large number of objects in a core data store using NSOperations to speed things up. I've followed all the Core Data multithreading rules - I've got a single persistent store coordinator and a managed object context per thread that on save is merging back to the main managed object context. The Problem When the number of threads running at once is more than 1, I get the exception logged on save of my core data store: NSExceptionHandler has recorded the following exception: NSInternalInconsistencyException -- optimistic locking failure What I've Tried My code that creates new entities is quite complex - it makes entities that have relationships with other entities that could be being created in a separate thread. If I replace my object creation routine with some very simple code just making non-related entries, everything works perfectly. Initially, as well as the exceptions, I was getting a save error saying core data couldn't save due to the merge failing. I read the docs and realised I needed a merge policy on the Managed Object Context I was saving to. I set this up and as this question states, the save error goes away, but the exception remains. My Question Do I need to worry about these exceptions? If I do need to get rid of the exceptions, any ideas on how I do it?

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• Timestamps and Intervals: NUMTOYMINTERVAL SYSTDATE CALCULATION SQL QUERY

  - by MeachamRob

  I am working on a homework problem, I'm close but need some help with a data conversion I think. Or sysdate - start_date calculation The question is: Using the EX schema, write a SELECT statement that retrieves the date_id and start_date from the Date_Sample table (format below), followed by a column named Years_and_Months_Since_Start that uses an interval function to retrieve the number of years and months that have elapsed between the start_date and the sysdate. (Your values will vary based on the date you do this lab.) Display only the records with start dates having the month and day equal to Feb 28 (of any year). DATE_ID START_DATE YEARS_AND_MONTHS_SINCE_START 2 Sunday , February 28, 1999 13-8 4 Monday , February 28, 2005 7-8 5 Tuesday , February 28, 2006 6-8 Our EX schema that refers to this question is simply a Date_Sample Table with two columns: DATE_ID NUMBER NOT Null START_DATE DATE I Have written this code: SELECT date_id, TO_CHAR(start_date, 'Day, MONTH DD, YYYY') AS start_date , NUMTOYMINTERVAL((SYSDATE - start_date), 'YEAR') AS years_and_months_since_start FROM date_sample WHERE TO_CHAR(start_date, 'MM/DD') = '02/28'; But my Years and months since start column is not working properly. It's getting very high numbers for years and months when the date calculated is from 1999-ish. ie, it should be 13-8 and I'm getting 5027-2 so I know it's not correct. I used NUMTOYMINTERVAL, which should be correct, but don't think the sysdate-start_date is working. Data Type for start_date is simply date. I tried ROUND but maybe need some help to get it right. Something is wrong with my calculation and trying to figure out how to get the correct interval there. Not sure if I have provided enough information to everyone but I will let you know if I figure it out before you do. It's a question from Murach's Oracle and SQL/PL book, chapter 17 if anyone else is trying to learn that chapter. Page 559.

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• Make form redirect users after posting

  - by Liso22

  I need to change a form so that instead of reloading the page after submitting it, it redirects the user to another page, this is the form: <form class="questionform" name="questionform-0" id="questionform-0"> <textarea class="question-box" cols="12" rows="5" id="question-box-' . $questionformid . '" name="title" type="text" maxlength="200" size="28"></textarea> <input type="text" class="ubicacion" value="" name="question"> <input type="button" name="ask" value="Publicar" onclick="askquestion('questionform-0'); window.location.reload(true);"> I want to remove the window.location.reload and change it for a redirect that sends users to the page their comment will appear. Which is: www.chusmix.com/s?= (the content of the second field) The problem is that the content of the second field is part of the url I want to redirect, it's not simply always the same URL. So I have no idea how to do it. How do I do it? Anyway thanks for any info or whatever that points me on the right direction. Thanks

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• Best ways to format LINQ queries.

  - by Aren B

  Before you ignore / vote-to-close this question, I consider this a valid question to ask because code clarity is an important topic of discussion, it's essential to writing maintainable code and I would greatly appreciate answers from those who have come across this before. I've recently run into this problem, LINQ queries can get pretty nasty real quick because of the large amount of nesting. Below are some examples of the differences in formatting that I've come up with (for the same relatively non-complex query) No Formatting var allInventory = system.InventorySources.Select(src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }).GroupBy(i => i.Region, i => i.Inventory); Elevated Formatting var allInventory = system.InventorySources .Select(src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }) .GroupBy( i => i.Region, i => i.Inventory); Block Formatting var allInventory = system.InventorySources .Select( src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }) .GroupBy( i => i.Region, i => i.Inventory ); List Formatting var allInventory = system.InventorySources .Select(src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }) .GroupBy(i => i.Region, i => i.Inventory); I want to come up with a standard for linq formatting so that it maximizes readability & understanding and looks clean and professional. So far I can't decide so I turn the question to the professionals here.

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• how to disable an onclick event?

  - by user1819709

  <form id="QandA" action="<?php echo htmlentities($action); ?>" method="post"> <table id="question"> <tr> <td colspan="2"> <a onclick="return plusbutton();"> <img src="Images/plussign.jpg" width="30" height="30" alt="Look Up Previous Question" class="plusimage" id="mainPlusbutton" name="plusbuttonrow"/> </a> <span id="plussignmsg">(Click Plus Sign to look up Previous Questions)</span> </td> </tr> </table> </form> In the code above I am able to replace an image with another image when the if statement is met. But my problem is that when the image is replaced, it does not disable the on click event. My question is that when the image is replaced, how do I disable the onclick event onclick="return plusbutton();?

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• Find all radio groups which haven't been selected

  - by nickf

  I have a basic quiz/survey type application I'm working on, and I'd like to give the user a prompt before they submit if they haven't answered all the questions. All the questions are multiple choice using radio buttons: <div class="question"> Q1: What is the second letter of the alphabet? <div class="choices"> <input type="radio" name="question_1" value="1" /> A <input type="radio" name="question_1" value="2" /> B <input type="radio" name="question_1" value="3" /> C </div> </div> <div class="question"> Q2: Which out of these is a berry? <div class="choices"> <input type="radio" name="question_2" value="1" /> Apples <input type="radio" name="question_2" value="2" /> Bananas <input type="radio" name="question_2" value="3" /> Carrots </div> </div> <div class="question"> ...etc How do you find which groups haven't got an option ticked? Or at least, if there are any which haven't been answered? jQuery is ok, and even preferred.

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• Is False == 0 and True == 1 in Python an implementation detail or guaranteed by the language?

  - by EOL

  Is it guaranteed that False == 0 and True == 1, in Python? For instance, is it in any way guaranteed that the following code will always produce the same results, whatever the version of Python (existing and in the foreseeable future)? 0 == False # True 1 == True # True ['zero', 'one'][False] # is 'zero' Any reference to the official documentation would be much appreciated! Other comments would be appreciated too… :) Edit: As noted in many answers, bool inherits from int. The question can therefore be recast as: "Is this an implementation detail that might change in the future, or does the documentation officially say that programmers can rely on booleans inheriting from integers?". This question is relevant for writing robust code that won't fail because of implementation details! Edit 2: The original question is still open, I believe (even though I accepted what I thought was the closest answer): even though Python 3 officially recognizes booleans as integers, I have not yet seen any official integer values for False and True… It therefore looks to me like it is best to stay clear from the assumption that False==0 and True==1.

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• is there a Java GUI for dummies ?

  - by MHero

  Hello, first I want to apologize about my english, it may be not clear enough. Well, I'm new to Java programming, and I search over this web about use of Swing, AWT, 2D, etc. but I didn't get the answer I was looking for. I want to know about a book or method to learn Java GUI programming (not even sure this is a propper term). Previous answers guide me to Filthy Rich Clients by Romain Guy and also to The Swing Tutorial in Sun Web Page. and No offense, but...the first one seems too complex and the second one a bit disorganize. so I ask about a more "for dummies" method. Thanks EDIT: Thanks everyboy, you're very kind and serious. I want to clear some things that I didn't state for being my first question. I dont' want to use autogenerated code(Don't want to say why only focus on my question for consistency) Also I've read Deitel & Deitel and it's a good beginners book but it seems to me that doesn't cover layout(and other details) Finally, I tried to read netbeans generated code but it's a mess find method by method and function by function the way that the IDE does it I hope this edition helps to solve my question

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• How to access parents' members from a inner class in WPF?

  - by black sensei

  Hello Experts! I'm trying to do scheduled operation let's say to check for user's credit left via web service call and update the user interface. i've tried with quartz.net to implement the scheduling bit.i created an inner class in the window class i need to update.That inner class has the method that calls the webservice and the result needs to be displayed back to the UI. here is an example of what i did. public partial class Window2 : Window { private int i; public Window2() { InitializeComponent(); } public class Myclass :IJob { public void Execute(JobExecutionContext context) { string result = doMyOperation(); //i'll like to call parent label member of name lblNotif //is something like parent.lblNotif.Content = result; //possible? } public string doMyOperation() { //calling the wermethod to retreive user's balance return result = service.GetUsersBalace(user); } } } Well the quartz bit is working and this post is not about quartz. here are my questions Question 1 : How is it possible to access Window2 controls, for instace lable lblNotif? Question 2 : If my thinking about this is wrong, what is done as best practice to solve my kind of problem, where an application need to do an operation let's say every 5mn and update the the UI. Question 3 : i at first tried to use the backgroundworker and i felt like i can't do the scheduling bit with it.Is that correct or i'm wrong. thanks for those who commented already and sorry for those who didn't get the meaning of my post.I hope this will be a bit clearer.Thanks for reading

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• Problem understanding Inheritance

  - by dhruvbird

  I've been racking my brains over inheritance for a while now, but am still not completely able to get around it. For example, the other day I was thinking about relating an Infallible Human and a Fallible Human. Let's first define the two: Infallible Human: A human that can never make a mistake. It's do_task() method will never throw an exception Fallible Human: A human that will occasionally make a mistakes. It's do_task() method may occasionally throw a ErrorProcessingRequest Exception The question was: IS an infallible human A fallible human OR IS a fallible human AN infallible human? The very nice answer I received was in the form of a question (I love these since it gives me rules to answer future questions I may have). "Can you pass an infallible human where a fallible human is expected OR can you pass a fallible human where an infallible human is expected?" It seems apparent that you can pass an infallible human where a fallible human is expected, but not the other way around. I guess that answered my question. However, it still feels funny saying "An infallible human is a fallible human". Does anyone else feel queasy when they say it? It almost feels as if speaking out inheritance trees is like reading out statements from propositional calculus in plain English (the if/then implication connectives don't mean the same as that in spoken English). Does anyone else feel the same?

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• Work with function references

  - by Ockonal

  Hello, I have another one question about functions reference. For example, I have such definition: typedef boost::function<bool (Entity &handle)> behaviorRef; std::map< std::string, ptr_vector<behaviorRef> > eventAssociation; The first question is: how to insert values into such map object? I tried: eventAssociation.insert(std::pair< std::string, ptr_vector<behaviorRef> >(eventType, ptr_vector<behaviorRef>(callback))); But the error: no matching function for call to ‘boost::ptr_vector<boost::function<bool(Entity&)> >::push_back(Entity::behaviorRef&)’ And I undersatnd it, but can't make workable code. The second question is how to call such functions? For example, I have one object of behaviorRef, how to call it with boost::bind with passing my own values?

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• Update table instantly or “Bulk” Update in database later? And is it advisable?

  - by Mestika

  Hi, I have a question regarding a semi-constant update in a database. In short it is regarding a checkout function on a web page, which each time the checkout function is evoked it do five steps. I want to try to optimize this function and have my eye on a step where I update a table each time the checkout is performed. I take the information retrieved from the shopping cart and then update the table in question. I do have some indexes on the table, the gain from those are greater than leaving them so this is a cost I’m willing to take. Now, my question is. Could it in some way regarding to performance be better to not update the table instantly but collect every checkout items and save them in some way (maybe in a file) and then at a specific time (or several times) at day take this file and then update the table with the new information. Then I started thinking about if there was a possibility to use some sort of Bulk Update to take a file, hashmap, array (or?) and then update it. And I’m using IBM DB2 version 9.7 Mestika

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• Passing huge amounts of data as an hexadecimal (0x123AB...) parameter of a clr stored procedure in s

  - by user193655

  I post this question has followup of This question, since the thread is not recieving more answers. I'm trying to understand if it is possible to pass as a parameter of a CLR stored procedure a large amount of data as "0x5352532F...". This is to avoid to send the data directly to the CLR stored procedure, instead of sending ti to a temporary DB field and from there passing it as varbinary(max) parmeter to the CLR stored procedure. I have a triple question: 1) is it possible, if yes how? Let's say i want to pass a pdf file to the CLR stored procedure (not the path, the full bits that make up the file). Something like: exec MyCLRStoredProcs.dbo.insertfile @file_remote_path ='c:\temp\test_file.txt' , @file_contents=0x4D5A90000300000004000.... --(this long list is the file content) where insertfile is a stored proc that writes to the server path (at file_remote_path) the binary data I pass as (file_contents). 2) is it there corruption risk of adopting this approach (or it is the same approach that sql server uses behind the scenes)? 3) how to convert the content of a file into the "0x23423..." hexadecimal representation

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• How to ask questions to an obstructionist?

  - by Rob Wells

  This is not related to my other recently posted question about "working with a star developer". In a similar vein, how do you work with someone who will only answer the specific question that you ask. I worked with someone who, when you asked a question on a specific aspect of the system, would give you the answer just related to the specific bit you'd asked about. For example, when processing radar messages I'd ask about an aspect of message number RJ546 and he would answer just about that specific part of RJ546. He wouldn't mention anything about the other freaky parts of the message, or mention any related aspects of the other messages. Then you'd go off and work on the processing and all of a sudden all this other freakiness would pop up. What's a good technique when working with this type of person? BTW I later found out that the person who I'd come in to replace had quit because he got sick and tired of having these surprises pop up due to the lack of information provided by this person. Edit: I forgot to add that the person was deliberately obstructionist and believed that job security came from hoarded knowledge not being disseminated.

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• How to learn a new programming language? And how to choose the appropriate language?

  - by Sebi

  Unfortunately my last question was closed, so I reformulated the question: I know this question was here a lot of times and can't be answered at all, but im not looking for a single name, but rather for an advice in my situation. I learned programming with Java and now I'm developing in Java for more or less 5 years (at the university) and I thinks my programming skills their are really ok/average. I have also small experience in C/C++ and C#. Now I have some spare time and I'd like to learn a new language or deepen the knowledge of Java/C/C++. But how to choose the right language to learn? I'd like to learn a language which will be usefull in the future concerning working in a software development business? I know there is no single answer, but I'm sure you could mention some languages that are more usefull than others. And what's the best way to learn such a language efficiently (bearing in mind that one has already learned some other languages)? Just doing tutorials? Or trying to implement a project? Trying to move a Java project to the new language?

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• Set all nonzero matrix elements to 1 (while keeping the others 0)

  - by Tomas Lycken

  I have a mesh grid defined as [X, Y, Z] = meshgrid(-100:100, -100:100, 25); % z will have more values later and two shapes (ovals, in this case): x_offset_1 = 40; x_offset_2 = -x_offset_1; o1 = ((X-x_offset_1).^2./(2*Z).^2+Y.^2./Z.^2 <= 1); o2 = ((X-x_offset_2).^2./(2*Z).^2+Y.^2./Z.^2 <= 1); Now, I want to find all points that are nonzero in either oval. I tried union = o1+o2; but since I simply add them, the overlapping region will have a value of 2 instead of the desired 1. How can I set all nonzero entries in the matrix to 1, regardless of their previous value? (I tried normalized_union = union./union;, but then I end up with NaN in all 0 elements because I'm dividing by zero...) Follow-up question: I got a perfect answer to my original question, but now I have a follow-up question on the same problem. I'm going to define a filled disc, c = (X.^2+Y.^2<R^2) that will also overlap with the two ovals. How do I find all the points that are inside the circle, but not inside any of the ovals?

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• Make UIViewController outside Navigation Controller

  - by user1447316

  i have a question for you. I'm working on this app that has a walkthrough/tutorial screens and also login ones. On each of this screens there is a button to skip this part and go directly to use the app, without completing the registration (you know, so that people can test it before signing-in). As you can see i'm using Storyboards. The NowPlaying04 ViewController is actually the app itself. Obviously, when the user will be a registered one, i should also be able to jump right back to that screen, skipping the walkthrough and signin process. The first question is: how is the best way to structure this? The second quesion is: how i can make a ViewController outside that Navigation controller. Cause as you can see now, the NowPlaying04 ViewController inherits the top navigation bar. Which is a thing that i don't want. I don't need that. I hope that you have understood my question. I'll appreciate any help. Programmatically or by dragging stuff around, i'm ok with all the solutions. The important thing is that it works correctly! :-)

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• Radiobutton validation.

  - by _sh

  The question is on the client side validation using java script. Significant parts of the program related to the question are given below.. ... <form name="results" action="" method="post"> ... <input type="radio" name="id" value="<%= id_edit %>" /> <!-- Don't bother about id_edit --> .... <input type="button" name="Edit" value="Edit" onclick="invoke(0)"><input type="button" name="Delete" value="Delete" onclick="return invoke(1)"> .... The script, function invoke(btn) { if(btn == 0) document.results.action="gev.do"; if(btn == 1) document.results.action="del.do"; document.results.submit(); } What basically i do is, depending on the selection of button, i pass a value to the servlet, either for updation or deletion. My question is, how can i validate the radiobutton, ie, i can any one help me out writing the js to validate if any one of the radio button is selected. All my efforts are in vein and i now use server side validation.

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• STL in C++ how does it work

  - by helloWorld

  I have very technical question, I was working with C, and now I'm studying C++, if I have for example this class class Team { private: list<Player> listOfPlayers; public: void addPlayer(string firstName, string lastName, int id) { Player newPlayer(string firstName, string lastName, int id); listOfPlayers.push_back(Player(string firstName, string lastName, int id)); } } this is a declaration of the Player: class Player{ private: string strLastName; string strFirstName; int nID; public: Player(string firstName, string lastName, int id); } and this is my constructor of Player: Player::Player(string firstName, string lastName, int id){ nId = id; string strFirstName = firstName; string strLastName = lastName; } so my question is when I call function addPlayer what exactly is going on with program, in my constructor of Account do I need to allocate new memory for new Account(cause in C I always use malloc) for strFirstName and strLastName, or constructor of string of Account and STL do it without me, thanks in advance (if you don't want to answer my question please at least give me some link with information) thanks in advance

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• Creating a multi-tenant application using PostgreSQL's schemas and Rails

  - by ramon.tayag

  Stuff I've already figured out I'm learning how to create a multi-tenant application in Rails that serves data from different schemas based on what domain or subdomain is used to view the application. I already have a few concerns answered: How can you get subdomain-fu to work with domains as well? Here's someone that asked the same question which leads you to this blog. What database, and how will it be structured? Here's an excellent talk by Guy Naor, and good question about PostgreSQL and schemas. I already know my schemas will all have the same structure. They will differ in the data they hold. So, how can you run migrations for all schemas? Here's an answer. Those three points cover a lot of the general stuff I need to know. However, in the next steps I seem to have many ways of implementing things. I'm hoping that there's a better, easier way. Finally, to my question When a new user signs up, I can easily create the schema. However, what would be the best and easiest way to load the structure that the rest of the schemas already have? Here are some questions/scenarios that might give you a better idea. Should I pass it on to a shell script that dumps the public schema into a temporary one, and imports it back to my main database (pretty much like what Guy Naor says in his video)? Here's a quick summary/script I got from the helpful #postgres on freenode. While this will probably work, I'm gonna have to do a lot of stuff outside of Rails, which makes me a bit uncomfortable.. which also brings me to the next question. Is there a way to do this straight from Ruby on Rails? Like create a PostgreSQL schema, then just load the Rails database schema (schema.rb - I know, it's confusing) into that PostgreSQL schema. Is there a gem/plugin that has these things already? Methods like "create_pg_schema_and_load_rails_schema(the_new_schema_name)". If there's none, I'll probably work at making one, but I'm doubtful about how well tested it'll be with all the moving parts (especially if I end up using a shell script to create and manage new PostgreSQL schemas). Thanks, and I hope that wasn't too long! UPDATE May 11, 2010 11:26 GMT+8 Since last night I've been able to get a method to work that creates a new schema and loads schema.rb into it. Not sure if what I'm doing is correct (seems to work fine, so far) but it's a step closer at least. If there's a better way please let me know. module SchemaUtils def self.add_schema_to_path(schema) conn = ActiveRecord::Base.connection conn.execute "SET search_path TO #{schema}, #{conn.schema_search_path}" end def self.reset_search_path conn = ActiveRecord::Base.connection conn.execute "SET search_path TO #{conn.schema_search_path}" end def self.create_and_migrate_schema(schema_name) conn = ActiveRecord::Base.connection schemas = conn.select_values("select * from pg_namespace where nspname != 'information_schema' AND nspname NOT LIKE 'pg%'") if schemas.include?(schema_name) tables = conn.tables Rails.logger.info "#{schema_name} exists already with these tables #{tables.inspect}" else Rails.logger.info "About to create #{schema_name}" conn.execute "create schema #{schema_name}" end # Save the old search path so we can set it back at the end of this method old_search_path = conn.schema_search_path # Tried to set the search path like in the methods above (from Guy Naor) # conn.execute "SET search_path TO #{schema_name}" # But the connection itself seems to remember the old search path. # If set this way, it works. conn.schema_search_path = schema_name # Directly from databases.rake. # In Rails 2.3.5 databases.rake can be found in railties/lib/tasks/databases.rake file = "#{Rails.root}/db/schema.rb" if File.exists?(file) Rails.logger.info "About to load the schema #{file}" load(file) else abort %{#{file} doesn't exist yet. It's possible that you just ran a migration!} end Rails.logger.info "About to set search path back to #{old_search_path}." conn.schema_search_path = old_search_path end end

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