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  • Django - 2 fields unique together

    - by webvulture
    Suppose, I want to record say poll choices by users everyday. In this case, i have a table named vote which has columns poll , choice and user-id . So how can i out the constraint (maybe in the django models or wherever possible) that poll and user-id both should not be the same for any entry but like the same user can vote for various different polls once and obviously various users can vote for the same poll. I hope I am clear.

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  • Preventing entire JOINed MYSQL query from failing when one field is missing within a WHERE clause

    - by filip o
    I am doing a couple of joins with a variable in the WHERE clause. I'm not sure if I am doing everything as efficiently as I could, or even using the best practices but my issue is that half my tables have data for when tableC.type=500, and the other half don't resulting in the entire query failing. SELECT tableA.value1 , tableB.value2, tableC.value3 FROM tableA JOIN tableB ON tableB.id=tableA.id JOIN tableC ON tableC.id=tableB.id WHERE tableA.category=$var && tableC.type=500; What I would like to happen is to still get tableA.value1 and tableB.value2 even if there is no field in tableC with a type=500. any thoughts? i'm totally stumped as how to approach this...

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  • How to get JOptionPane with three text fields

    - by Dr.Mostafa
    I want to know how i can do a messageBox from three input dialog .. Like this: JOptionPane.showInputMessageDialog("Enter your FirstName"); JOptionPane.showInputMessageDialog("Enter your MiddleName"); JOptionPane.showInputMessageDialog("Enter your LastName"); But I want one message has a three input boxes.

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  • Adding fields until screen is full

    - by Eric
    For the sake of this question, let us suppose that I want a row of buttons. I want to put as many buttons in that row as I can fit on the screen, but no more. In other words, as long as a prospective button will not be cut off or have its text shortened, add it. It seems that I should be able to do something like: HorizontalFieldManager hfm = new HorizontalFieldManager(); int remainingWidth = Display.getWidth(); int i =0; while(true) { ButtonField bf = new ButtonField("B " + i); remainingWidth -= bf.getWidth(); if(remainingWidth<0) break; hfm.add(bf); i++; } add(hfm); But this doesn't work. bf.getWidth() is always 0. I suspect that this is because the button has not yet been laid out when I query for the width. So, perhaps I could just make sure the buttons are always the same size. But this won't work for a few reasons: Different BB platforms have different looks for buttons and text that will fit on a button on a Curve won't fit on a button on a Storm. 3rd party themes may change the look of buttons, so I can't even count on buttons being a certain size on a certain platform. Is there no way for me to actually check the remaining space before adding a button? It feels like a fairly useful feature; am I just missing something?

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  • How to load/save C++ class instance (using STL containers) to disk

    - by supert
    I have a C++ class representing a hierarchically organised data tree which is very large (~Gb, basically as large as I can get away with in memory). It uses an STL list to store information at each node plus iterators to other nodes. Each node has only one parent, but 0-10 children. Abstracted, it looks something like: struct node { public: node_list_iterator parent; // iterator to a single parent node double node_data_array[X]; map<int,node_list_iterator> children; // iterators to child nodes }; class strategy { private: list<node> tree; // hierarchically linked list of nodes struct some_other_data; public: void build(); // build the tree void save(); // save the tree from disk void load(); // load the tree from disk void use(); // use the tree }; I would like to implement the load() and save() to disk, and it should be fairly fast, however the obvious problems are: I don't know the size in advance; The data contains iterators, which are volatile; My ignorance of C++ is prodigious. Could anyone suggest a pure C++ solution please?

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  • How to map a search object to a class with more fields with JPA annotations

    - by Moli
    Hi all, I'm a newbie with JPA. I need to map a search object to a table. The search object has only and id, name. The big object has more fileds id, name, adress and more. I use this as big object view plaincopy to clipboardprint? I use this as big object @Entity @Table(name="users") public class User { @Id @GeneratedValue(strategy = GenerationType.AUTO) private long id; private String name; private String adress; private String keywords; } //this is my search object @XXX public class UserSearch { @Id @GeneratedValue(strategy = GenerationType.AUTO) private long id; private String name; } What annotations I need to use to map the search object to the table users? I'm using spring+struts2+hibernate+JPA. Help is appreciated! Thanks!

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  • "Overriding" instance variables in subtype: Possible risks?

    - by sebastiangeiger
    Say I had a class SuperClass and two subclasses SubClassA and SubClassB that inherit from SuperClass. abstract class SuperClass{ ... List someList; ... } class SubClassA extends SuperClass{ ... List<String> someList; ... } class SubClassB extends SuperClass{ ... List<Integer> someList; ... } That way it is convenient because I can get someList.size() in Superclass and have Typesafety in the Subclasses. The problem is that it does not "feel" right, can you think of potential hazards this apporach has that I am not aware of?

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  • Ruby on Rails: instance & class variables not maintaining value in controller

    - by DerNalia
    at the top of my controller, outside of any method, I have @@javascript_is_disabled = false and I have methods that that the view calls and invokes something like this @@javascript_is_disabled = params[:javascript_disabled] but when I need the @@javascript_is_disabled in completely different method.. it is always false. I know it changes in the method with params args... cause those methods behave differently, and appropriately And ideas?

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  • Are your redirects HTTP compliant (absolute URI)?

    - by webbiedave
    In the Hypertext Transfer Protocol 1.1 spec, it states for the Location header: The field value consists of a single absolute URI. Location = "Location" ":" absoluteURI An example is: Location: http://www.w3.org/pub/WWW/People.html I have coded many an app that doesn't include the scheme and domain (i.e., /thankyou/) and every browser I've ever tested with redirects correctly. I'm wondering if it's imperative to go back and change all my redirect code or just ignore this part of the spec. Have many of you produced code that doesn't comply and will you go back and change it? Or will you just trust that clients will continue to resolve them well into the future? (going forward I will certainly adhere to this)

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  • Retrieve POST data without knowing exact number of fields

    - by James
    Hi all! I'm creating an online poll from scratch which will be held in a database. I'm working on getting a system set up so someone can create a new poll. I will be having the user fill out a simple HTML form with the Questions and Answers (there may be several answers). The user will be able to add multiple questions and multiple answers for each question. As the total number of questions and answers will be decided by the user, I need to create some clever PHP to cater for this - however many there are. When dealing with a static number of questions, it's simple. But I'm having trouble thinking of a way to get all the POST data into individual PHP variables so I can process them. I was thinking of using a foreach loop, anyone got any ideas? Sorry for the long winded description! If anyone needs anything clarified, I'd be happy to do so. My problem is that I can't get my head around how to deal with the POST values when I don't know exactly which element of the array will contain what. If things were static with a set number of questions and answers, I'd know $_POST[0] was Question1, etc Thank you! =)

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  • Ruby & ActiveRecord: referring to integer fields by (uniquely mapped) strings

    - by JP
    While its not my application a simple way to explain my problem is to assume I'm running a URL shortener. Rather than attempt to try and figure out what the next string I should use as the unique section of the URL, I just index all my URLs by integer and map the numbers to strings behind the scenes, essentially just changing the base of the number to, let's say, 62: a-z + A-Z + 0-9. In ActiveRecord I can easily alter the reader for the url_id field so that it returns my base 62 string instead of the number being stored in the database: class Short < ActiveRecord::Base def url_id i = read_attribute(:convo) return '0' if i == 0 s = '' while i > 0 s << CHARS[i.modulo(62)] i /= 62 end s end end but is there a way to tell ActiveRecord to accept Short.find(:first,:conditions=>{:url_id=>'Ab7'}), ie. putting the 'decoding' logic into my Short ActiveRecord class? I guess I could define my own def self.find_by_unique_string(string), but that feels like cheating somehow! Thanks!

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  • Why is Apache + Rails is spitting out two status headers for code 500?

    - by Daniel Beardsley
    I have a rails app that is working fine except for one thing. When I request something that doesn't exist (i.e. /not_a_controller_or_file.txt) and rails throws a "No Route matches..." exception, the response is this (blank line intentional): HTTP/1.1 200 OK Date: Thu, 02 Oct 2008 10:28:02 GMT Content-Type: text/html Content-Length: 122 Vary: Accept-Encoding Keep-Alive: timeout=15, max=100 Connection: Keep-Alive Status: 500 Internal Server Error Content-Type: text/html <html><body><h1>500 Internal Server Error</h1></body></html> I have the ExceptionLogger plugin in /vendor, though that doesn't seem to be the problem. I haven't added any error handling beyond the custom 500.html in public (though the response doesn't contain that HTML) and I have no idea where this bit of html is coming from. So Something, somewhere is adding that HTTP/1.1 200 status code too early, or the Status: 500 too late. I suspect it's Apache because I get the appropriate HTTP/1.1 500 header (at the top) when I use Webrick. My production stack is as follows: Apache 2 Mongrel (5 instances) RubyOnRails 2.1.1 (happens in both 1.2 and 2.1.1) I forgot to mention, the error is caused by a "no route matches..." exception

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  • Correct approach to validate attributes of an instance of class

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Javascript - Simple form script to hide/show fields

    - by danit
    Im looking for a simple script in javascript that i can extend, at a basic level Im looking to show 1 field based on which option from a <select> the user chooses. <select id="options"> <option value="spoon">Spoon</option> <option value="form">Fork</option> </select> if select=spoon { <input>enter your favorite soup</input> } else { <input>Your gonna need a knife</input> } Simple JS is the key!

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  • How to get a list of users for all instance's databases

    - by stee1rat
    I guess the procedure should be something like this: declare @db varchar(100) declare @user varchar(100) declare c cursor for select name from sys.sysdatabases open c fetch next from c into @db while @@fetch_status = 0 begin print @db exec ('use ' + @db) declare u cursor for select name from sys.sysusers where issqlrole <> 1 and hasdbaccess <> 0 and isntname <> 1 open u fetch next from u into @user while @@fetch_status = 0 begin print @user fetch next from u into @user end print '--------------------------------------------------' close u deallocate u fetch next from c into @db end close c deallocate c But the problem is that exec ('use ' + @db) doesn't work. And i always get user list of currently chosen database. How should i fix that? P.S.: I want this code to work on both 2000 and 2005 sql servers.

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  • Android Static Variable Scope and Lifetime

    - by Edison
    I have an application that has a Service uses a ArrayList to store in the background for a very long time, the variable is initialized when the service started. The service is in the background and there will be frequent access to the variable (that's why i don't want to use file management or settings since it will be very expensive for a file I/O for the sake of battery life). The variable will likely to be ~1MB-2MB over its life tie. Is it safe to say that it will never be nulled by GC or the system or is there any way to prevent it? Thanks.

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  • SQL Select between two fields depending on the value of one field

    - by Filip
    Hi. I am using a PostgreSQL database, and in a table representing some measurements I've two columns: measurement, and interpolated. In the first I've the observation (measurement), and b is the interpolated value depending on nearby values. Every record with an original value has also an interpolated value. However, there are a lot of records without "original" observations (NULL), hence the values are interpolated and stored in the second column. So basically there are just two cases in the database: Value Value NULL Value Of course, it is preferable to use the value from the first column if available, hence I need to build a query to select the data from the first column, and if not available (NULL), then the database returns the value from the second column for the record in question. I have no idea how to build the SQL query. Please help. Thanks.

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  • C# - Making fields/properties read only conditionally

    - by Alistair77
    I have three classes; Classes A and B both reference class C. How can I make it so members of class C can be modified when referenced from class A but not modified when referenced from class B? IE, the following should be possible; classA myClassA = new classA(); myClassA.myClassC.IssueNumber = 3; But this should not be possible; classB myClassB = new classB(); myClassB.myClassC.IssueNumber = 3; Making classB.classC read-only still allows properties of classC to be altered. I'm sure this is basic stuff but can't find a simple answer. Thanks, A

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  • C++ Unions bit fields task

    - by learningtolive
    Can somebody clear me out why would I use union and with what purpose the same address for the cin'ed variable and bit field (task from the Schildts C++ book)? In other words why would I use union for : char ch; struct byte bit; // Display the ASCII code in binary for characters. #include <iostream> #include <conio.h> using namespace std; // a bit field that will be decoded struct byte { unsigned a : 1; unsigned b : 1; unsigned c : 1; unsigned d : 1; unsigned e : 1; unsigned f : 1; unsigned g : 1; unsigned h : 1; }; union bits { char ch; struct byte bit; } ascii ; void disp_bits(bits b); int main() { do { cin >> ascii.ch; cout << ": "; disp_bits(ascii); } while(ascii.ch!='q'); // quit if q typed return 0; } // Display the bit pattern for each character. void disp_bits(bits b) { if(b.bit.h) cout << "1 "; else cout << "0 "; if(b.bit.g) cout << "1 "; else cout << "0 "; if(b.bit.f) cout << "1 "; else cout << "0 "; if(b.bit.e) cout << "1 "; else cout << "0 "; if(b.bit.d) cout << "1 "; else cout << "0 "; if(b.bit.c) cout << "1 "; else cout << "0 "; if(b.bit.b) cout << "1 "; else cout << "0 "; if(b.bit.a) cout << "1 "; else cout << "0 "; cout << "\n"; }

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