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  • How to create multiple tables with the same schema using SQLite jdbc

    - by Space_C0wb0y
    I want to split a large table horizontally, and I would like to make sure that all three of them have the same schema. Currently I am using this piece of code to create the tables: statement .executeUpdate("CREATE TABLE AnnotationsMolecularFunction (Id INTEGER PRIMARY KEY ASC AUTOINCREMENT, " + "ProteinId NOT NULL, " + "GOId NOT NULL, " + "UNIQUE (ProteinId, GOId)" + "FOREIGN KEY(ProteinId) REFERENCES Protein(Id))"); There is one such statement for each table. This is bad, because if I decide to change the schema later (which will most certainly happen), I will have to change it three times, which begs for errors, so I would like a way to make sure that the other tables have the same schema without explicitly writing it again. I can use: statement .executeUpdate("CREATE TABLE AnnotationsBiologicalProcess AS SELECT * FROM AnnotationsMolecularFunction"); to create the other tables with the same columns, but the constraints are not aplied. I could of course just generate the same query-string three times with different table-names in Java, but I would like to know if there is an SQL-way of achieving this.

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  • symfony: multiple apps, single login?

    - by gruner
    My symfony project is divided into several apps. Using the sfDoctrineGuard plugin I'd like to create another app just for login, and redirect to the appropriate app after login. My questions: • Is this advisable or does it go against how sfGuard is supposed to work? • Is there a way to redirect between applications without hardcoding the entire url? Is there a "symfony way" of doing it, or is this not how projects are supposed to function? (All I can find is this thread which is kind of vague on the specifics.)

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  • android multiple activity declaration in manifest

    - by Brahadeesh
    Hi all. I have a main activity. From it, I am calling 2 other sub activities called FacebookLogin and Twitterlogin. I am using the following code in AndroidManufest.xml: ..... <activity android:name=".*****" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> <intent-filter android:label="@string/app_name"> <action android:name="android.intent.action.SEND" /> <category android:name="android.intent.category.DEFAULT" /> <data android:mimeType="text/plain" /> </intent-filter> </activity> <activity android:name=".FacebookLogin" android:label="string/app_name"> <intent-filter android:label="@string/app_name"> <action android:name="android.intent.action.SEND" /> <category android:name="android.intent.category.DEFAULT" /> <data android:mimeType="image/*" /> </intent-filter> </activity> <activity android:name=".TwitterLogin" android:label="string/app_name"> <intent-filter> <action android:name="android.intent.action.VIEW"></action> <category android:name="android.intent.category.DEFAULT"></category> <category android:name="android.intent.category.BROWSABLE"></category> <data android:scheme="yourapp" android:host="twitt"></data> </intent-filter> </activity> ..... Am i doing it right? Should i nest the FacebookLogin and TwitterLogin activities in the main activity? The aforesaid 2 classes are in the package com.examples.. * is the same wherever used.

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  • Regarding Multiple Tab-Class

    - by Christine
    Hi! I've problem regarding GUI with one Menu and one Order Class. I've created a variable to store how many items have been selected in the Menu Class. private int totalSelected; The var totalSelected is live updated. It can be changed anytime depending on actionPerformed() function.(Exp: totalSelected will add up all the selected items) In the Order Class, how can I access to the live update variable totalSelected in order to retrieve the live update value? When I invoke getTotalSelected() function inside the Menu Class, I will only obtain a 0 value. Thanks for your help ^^!

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  • Symfony: embedRelation() controlling options for nesting multiple levels of relations

    - by wulftone
    Hey all, I'm trying to set some conditional statements for nested embedRelation() instances, and can't find a way to get any kind of option through to the second embedRelation. I've got a "Measure-Page-Question" table relationship, and I'd like to be able to choose whether or not to display the Question table. For example, say I have two "success" pages, page1Success.php and page2Success.php. On page1, I'd like to display "Measure-Page-Question", and on page2, I'd like to display "Measure-Page", but I need a way to pass an "option" to the PageForm.class.php file to make that kind of decision. My actions.class.php file has something like this: // actions.class.php $this-form = new measureForm($measure, array('option'=$option)); to pass an option to the "Page", but passing that option through "Page" into "Question" doesn't work. My measureForm.class.php file has an embedRelation in it that is dependent on the "option": // measureForm.class.php if ($this-getOption('option') == "page_1") { $this-embedRelation('Page'); } and this is what i'd like to do in my pageForm.class.php file: // pageForm.class.php if ($this-getOption('option') == "page_1") { // Or != "page_2", or whatever $this-embedRelation('Question'); } I can't seem to find a way to do this. Any ideas? Is there a preferred Symfony way of doing this type of operation, perhaps without embedRelation? Thanks, -Trevor As requested, here's my schema.yml: # schema.yml Measure: connection: doctrine tableName: measure columns: _kp_mid: type: integer(4) fixed: false unsigned: false primary: true autoincrement: true description: type: string() fixed: false unsigned: false primary: false notnull: false autoincrement: false frequency: type: integer(4) fixed: false unsigned: false primary: false notnull: false autoincrement: false relations: Page: local: _kp_mid foreign: _kf_mid type: many Page: connection: doctrine tableName: page columns: _kp_pid: type: integer(4) fixed: false unsigned: false primary: true autoincrement: true _kf_mid: type: integer(4) fixed: false unsigned: false primary: false notnull: false autoincrement: false next: type: string() fixed: false unsigned: false primary: false notnull: false autoincrement: false number: type: string() fixed: false unsigned: false primary: false notnull: false autoincrement: false previous: type: string() fixed: false unsigned: false primary: false notnull: false autoincrement: false relations: Measure: local: _kf_mid foreign: _kp_mid type: one Question: local: _kp_pid foreign: _kf_pid type: many Question: connection: doctrine tableName: question columns: _kp_qid: type: integer(4) fixed: false unsigned: false primary: true autoincrement: true _kf_pid: type: integer(4) fixed: false unsigned: false primary: false notnull: false autoincrement: false text: type: string() fixed: false unsigned: false primary: false notnull: false autoincrement: false type: type: integer(4) fixed: false unsigned: false primary: false notnull: false autoincrement: false relations: Page: local: _kf_pid foreign: _kp_pid type: one

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  • Fetch data from multiple MySQL tables

    - by Jon McIntosh
    My two tables look like this: TABLE1 TABLE2 +--------------------+ +--------------------+ |field1|field2|field3| and |field2|field4|field5| +--------------------+ +--------------------+ I am already running a SELECT query for TABLE1, and assorting all of the data into variables: $query = "SELECT * FROM TABLE1 WHERE field2 = 2"; $result = mysql_query($query); $num_rows = mysql_num_rows($result); if((!is_bool($result) || $result) && $num_rows) { while($row = mysql_fetch_array($result)) { $field1 = $row['field1']; $field2 = $row['field2']; $field3 = $row['field3']; } } What I want to do is get the data from 'field4' on TABLE2 and add it to my variables. I would want to get field4 WHERE field2 = 2

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  • Javascript callback for multiple ajax calls

    - by Jisaak
    My lack of javascript knowledge is getting me in trouble again. I think this should be a fairly easy problem to fix but I cant figure it out. Situation: I want to make three ajax calls in a click event. Each ajax call does a distinct operation and returns back data that is needed for a final callback. The calls themselves are not dependent on one another, they can all go at the same time, however I would like to have a final callback when all three are complete. $('#button').click(function() { fun1(); fun2(); fun3(); //now do something else when the requests have done their 'sucess' callbacks. }); var fun1= (function() { $.ajax({/*code*/}); }); var fun2 = (function() { $.ajax({/*code*/}); }); var fun3 = (function() { $.ajax({/*code*/}); });

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  • jitter if multiple outliers in ggplot2 boxplot

    - by Andreas
    I am trying to find a suitable display to illustrate various properties within and across school classes. For each class there is only 15-30 data points (pupils). Right now i am leaning towards a whisker-less boxplot, showing only 1.,2. and 3. quartile + datapoints more then e.g. 1 population SD +/- the sample median. This I can do. However - I need to show this graph to some teachers, in order to gauge what they like most. I'd like to compare my graph with a normal boxplot. But the normal boxplot looks the same if there is only one outlier, or e.g. 5 outliers at the same value. In this case this would be a deal-breaker. e.g. test <-structure(list(value = c(3, 5, 3, 3, 6, 4, 5, 4, 6, 4, 6, 4, 4, 6, 5, 3, 3, 4, 4, 4, 3, 4, 4, 4, 3, 4, 5, 6, 6, 4, 3, 5, 4, 6, 5, 6, 4, 5, 5, 3, 4, 4, 6, 4, 4, 5, 5, 3, 4, 5, 8, 8, 8, 8, 9, 6, 6, 7, 6, 9), places = structure(c(1L, 2L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 2L, 1L), .Label = c("a", "b"), class = "factor")), .Names = c("value", "places"), row.names = c(NA, -60L), class = "data.frame") ggplot(test, aes(x=places,y=value))+geom_boxplot() Here there are two outliers at ("a",9) - but only one "dot" shown. So my question: How to jitter the outliers. And - what kind of display would you suggest for this kind of data?

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  • mysql: Average over multiple columns in one row, ignoring nulls

    - by Sai Emrys
    I have a large table (of sites) with several numeric columns - say a through f. (These are site rankings from different organizations, like alexa, google, quantcast, etc. Each has a different range and format; they're straight dumps from the outside DBs.) For many of the records, one or more of these columns is null, because the outside DB doesn't have data for it. They all cover different subsets of my DB. I want column t to be their weighted average (each of a..f have static weights which I assign), ignoring null values (which can occur in any of them), except being null if they're all null. I would prefer to do this with a simple SQL calculation, rather than doing it in app code or using some huge ugly nested if block to handle every permutation of nulls. (Given that I have an increasing number of columns to average over as I add in more outside DB sources, this would be exponentially more ugly and bug-prone.) I'd use AVG but that's only for group by, and this is w/in one record. The data is semantically nullable, and I don't want to average in some "average" value in place of the nulls; I want to only be counting the columns for which data is there. Is there a good way to do this? Ideally, what I want is something like UPDATE sites SET t = AVG(a*a_weight,b*b_weight,...) where any null values are just ignored and no grouping is happening.

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  • jQuery ajax form submit - multiple post/get requests caused when validation fails

    - by kenny99
    Hi, I have a problem where if a form submission (set up to submit via AJAX) fails validation, the next time the form is submitted, it doubles the number of post requests - which is definitely not what I want to happen. I'm using the jQuery ValidationEngine plugin to submit forms and bind validation messages to my fields. This is my code below. I think my problem may lie in the fact that I'm retrieving the form action attribute via $('.form_container form').attr('action') - I had to do it this way as using $(this).attr was picking up the very first loaded form's action attr - however, when i was loading new forms into the page it wouldn't pick up the new form's action correctly, until i removed the $(this) selector and referenced it using the class. Can anyone see what I might be doing wrong here? (Note I have 2 similar form handlers which are loaded on domready, that could also be an issue) $('input#eligibility').live("click", function(){ $(".form_container form").validationEngine({ ajaxSubmit: true, ajaxSubmitFile: $('.form_container form').attr('action'), success : function() { var url = $('input.next').attr('rel'); ajaxFormStage(url); }, failure : function() { //unique stuff for this form } }); }); //generic form handler - all form submissions not flagged with the #eligibility id $('input.next:not(#eligibility)').live("click", function(){ $(".form_container form").validationEngine({ ajaxSubmit: true, ajaxSubmitFile: $('.form_container form').attr('action'), success : function() { var url = $('input.next').attr('rel'); ajaxFormStage(url); }, failure : function() { } }); });

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  • Multiple range product in Python

    - by Tyr
    Is there a better way to do this: perms = product(range(1,7),range(1,7),range(1,7)) so that I can choose how many ranges I use? I want it to be equivalent to this, but scalable. def dice(num) if num == 1: perms = ((i,) for i in range(1,7)) elif num == 2: perms = product(range(1,7),range(1,7)) elif num == 3: perms = product(range(1,7),range(1,7),range(1,7)) #... and so on but I know there has to be a better way. I'm using it for counting dice outcomes. The actual code def dice(selection= lambda d: d[2]): perms = itertools.product(range(1,7),range(1,7),range(1,7)) return collections.Counter(((selection(sorted(i)) for i in perms))) where I can call it with a variety of selectors, like sum(d[0:2]) for the sum of the lowest 2 dice or d[1] to get the middle dice.

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  • ExtJS Data Grid Column renderer to have multiple values

    - by Podlsk
    Hi, I am wondering if it is possible in ExtJS to have several values of the data source available to the renderer of the column. For example with the "Actions" column, the id is passed to the renderer. However I require both the user_id and id passed to the render. How may I do this? table_cols = [{ header: "User ID", width: 30, sortable: true, dataIndex: 'user_id' }, { header: "Actions", width: 60, sortable: false, dataIndex: 'id', renderer: function(val) { //IF USER ID MEETS A CONSTRAINT PRINT THE ID } }]; Thanks.

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  • jquery find and replace multiple items

    - by client
    I have a monthly table that needs to be translated for each languages Something like this (doesnt work obviously) $('.lang-en #monthly th').each(function() { var text = $(this).text(); $(this).text(text.replace('Tam', 'Jan')); $(this).text(text.replace('Hel', 'Feb')); $(this).text(text.replace('Maa', 'Mar')); $(this).text(text.replace('Huh', 'Apr')); $(this).text(text.replace('Tou', 'May')); $(this).text(text.replace('Kes', 'Jun')); $(this).text(text.replace('Hei', 'Jul')); $(this).text(text.replace('Elo', 'Aug')); $(this).text(text.replace('Syy', 'Sep')); $(this).text(text.replace('Lok', 'Oct')); $(this).text(text.replace('Mar', 'Nov')); $(this).text(text.replace('Jou', 'Dec')); $(this).text(text.replace('Yht', 'Total')); });

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  • Sqlite table constraint - unique on multiple columns

    - by Rich
    I can find syntax "charts" on this on the sqlite website, but no examples and my code is crashing. I have other tables with unique constraints on a single column, but I want to add a constraint to the table on two columns. This is what I have that is causing a SQLiteException with the message "syntax error". CREATE TABLE name (column defs) UNIQUE (col_name1, col_name2) ON CONFLICT REPLACE I'm doing this based on the following: table-constraint

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  • Django models: Use multiple values as a key?

    - by Rosarch
    Here is a simple model: class TakingCourse(models.Model): course = models.ForeignKey(Course) term = models.ForeignKey(Term) Instead of Django creating a default primary key, I would like to use both course and term as the primary key - taken together, they uniquely identify a tuple. Is this allowed by Django? On a related note: I am trying to represent users taking courses in certain terms. Is there a better way to do this? class Course(models.Model): name = models.CharField(max_length=200) requiredFor = models.ManyToManyField(RequirementSubSet, blank=True) offeringSchool = models.ForeignKey(School) def __unicode__(self): return "%s at %s" % (self.name, self.offeringSchool) class MyUser(models.Model): user = models.ForeignKey(User, unique=True) takingReqSets = models.ManyToManyField(RequirementSet, blank=True) takingTerms = models.ManyToManyField(Term, blank=True) takingCourses = models.ManyToManyField(TakingCourse, blank=True) school = models.ForeignKey(School) class TakingCourse(models.Model): course = models.ForeignKey(Course) term = models.ForeignKey(Term) class Term(models.Model): school = models.ForeignKey(School) isPrimaryTerm = models.BooleanField()

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  • Using Multiple File Handles for Single File

    - by Ryan Rosario
    I have an O(n^2) operation that requires me to read line i from a file, and then compare line i to every line in the file. This repeats for all i. I wrote the following code to do this with 2 file handles, but it does not yield the result I am looking for. I imagine this is a simple error on my part. IN1 = open("myfile.dat","r") IN2 = open("myfile.dat","r") for line1 in IN1: for line2 in IN2: print line1.strip(), line2.strip() IN1.close() IN2.close() The result: Hello Hello Hello World Hello This Hello is Hello an Hello Example Hello of Hello Using Hello Two Hello File Hello Pointers Hello to Hello Read Hello One Hello File The output should contain 15^2 lines.

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  • C# WinForms. Multiple Forms in separate threads

    - by Calum Murray
    I'm trying to run an ATM Simulation in C# with Windows Forms that can have more than one instance of an ATM machine transacting with a bank account simultaneously. The idea is to use semaphores/locking to block critical code that may lead to race conditions. My question is this: How can I run two Forms simultaneously on separate threads? In particular, how does all of this fit in with the Application.Run() that's already there? Here's my main class: public class Bank { private Account[] ac = new Account[3]; private ATM atm; public Bank() { ac[0] = new Account(300, 1111, 111111); ac[1] = new Account(750, 2222, 222222); ac[2] = new Account(3000, 3333, 333333); Application.Run(new ATM(ac)); } static void Main(string[] args) { new Bank(); } } ...that I want to run two of these forms on separate threads... public partial class ATM : Form { //local reference to the array of accounts private Account[] ac; //this is a reference to the account that is being used private Account activeAccount = null; private static int stepCount = 0; private string buffer = ""; // the ATM constructor takes an array of account objects as a reference public ATM(Account[] ac) { InitializeComponent(); //Sets up Form ATM GUI in ATM.Designer.cs this.ac = ac; } ... I've tried using Thread ATM2 = new Thread(new ThreadStart(/*What goes in here?*/)); But what method do I put in the ThreadStart constructor, since the ATM form is event-driven and there's no one method controlling it? Thanks, Calum

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  • How can I build multiple processes with TBB?

    - by Jackie
    Now I plan to parallelize my sequential solver. I hope I could run several copies of my solver(maybe with different parameters) in parallel simultaneously on a multi-core computer. can I do this with TBB? The reason I ask this question is that the book says: do not introduce anything in your code that will not allow single-thread execution. Any experts can explain this issue? Thanks.

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  • How to cache queries in Rails across multiple requests

    - by m.u.sheikh
    I want to cache query results so that the same results are fetched "for more than one request" till i invalidate the cache. For instance, I want to render a sidebar which has all the pages of a book, much like the index of a book. As i want to show it on every page of the book, I have to load it on every request. I can cache the rendered sidebar index using action caching, but i also want to actually cache the the query results which are used to generate the html for the sidebar. Does Rails provide a way to do it? How can i do it?

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  • Parsing atom/rss feed containing multiple <link> tags with Haml on RoR

    - by fenderplayer
    So, firstly, heres an atom feed snippet which i am trying to parse: // http://somelink.com/atom <feed xmlns="http://www.w3.org/2005/Atom"> <entry> <title>Title Here</title> <link href="http://somelink.com/link1&amp;amp;ref=rss" rel="alternate" /> <link href="http://somelink.com/link2&amp;amp;ref=rss" rel="tag:somelink.com/apply_url"/> ... </entry> i pull the atom feed like so, // In controller index method @rss = SimpleRSS.parse open('http://somelink.com/atom') Then i output the response in the view, which i am writing using haml, as follows: - @rss.entries.each do |item| .title-div = item.title .title-link = item.link //outputs the first link I could run a second loop for the links but is there a way to get the second link without it? Like reading the "rel" attribute and outputting the correct link? How do i do this in haml/rails?

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  • Setting up multiple areas in sharp MVC2 - SharpArchitecture 1.6

    - by Hamid
    Im using sharp architecture 1.6 framework to create a MVC2 app. I have two areas, "Business", "Content". Im using BusinessAreaRegistration.cs and ContentAreaRegistration.cs to register the areas by using AreaRegistration.RegisterAllAreas(). The Content area gets routed just fine, but the business area does not work at all. gooing to /business/businessObjects/ show the error Server Error in '/' Application. The resource cannot be found. How can I register both areas properly?

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  • adding multiple <asp:Hyperlink>s into a repeater

    - by Colin Pickard
    I have a repeater control, and I want to put an unknown number of <asp:Hyperlink>s into the template, for example if you start with this: <asp:Repeater runat="server" ID="PetsRepeater"> <ItemTemplate> <%#DataBinder.Eval(Container.DataItem, "Owner")%> <%#this.ListPets(Container.DataItem)%> </ItemTemplate> </asp:Repeater> and in code behind: public partial class test1 : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack) { PetOwner p = new PetOwner() { Owner = "Jimmy", PetNames = new List<String>() { "Nemo", "Dory" } }; List<PetOwner> PetOwners = new List<PetOwner>() { p }; PetsRepeater.DataSource = PetOwners; PetsRepeater.DataBind(); } } protected String ListPets(Object PetOwner) { StringBuilder sb = new StringBuilder(); foreach (String Name in ((PetOwner)PetOwner).PetNames) { if (sb.Length > 0) sb.Append(", "); sb.Append(Name); } return sb.ToString(); } } class PetOwner { public String Owner; public List<String> PetNames; } Now suppose instead of having the string "Nemo, Dory" in my repeater, I want something like this: <asp:HyperLink runat=server Text="Nemo" NavigateUrl="Pet.aspx?Name=Nemo" />, <asp:HyperLink runat=server Text="Dory" NavigateUrl="Pet.aspx?Name=Dory" /> How can I do that? I tried putting a foreach inline in the aspx page, but I get the error Invalid expression term 'foreach'.

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  • best practices - multiple functions vs single function with switch case

    - by Amit
    I have a situation where I need to perform several small (but similar) tasks. I can think of two ways to achieve this. First Approach: function doTask1(); function doTask2(); function doTask3(); function doTask4(); Second Approach: // TASK1, TASK2, ... TASK4 are all constants function doTask(TASK) { switch(TASK) { case TASK1: // do task1 break; case TASK2: // do task2 break; case TASK3: // do task3 break; case TASK4: // do task4 break; } } A few more tasks may be added in future (though the chances are rare. but this cannot be ruled out) Please suggest which of the two approaches (or if any other) is a best practice in such a situation.

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  • How can I disable multiple links with jQuery?

    - by Samantha J
    I have the following HTML: <a title="Login" data-href="/MyAccount/Access/Login" data-title="Admin" data-entity="n/a" id="loginLink" class="nav-button dialogLink"><b>Login</b></a> <a title="Register" data-href="/MyAccount/Access/Register" data-title="Admin" data-entity="n/a" id="registerLink" class="nav-button dialogLink"><b>Register</b></a> When a user clicks on the #loginLink or #registerLink I would like to disable the link and call a dialog script. I created the following function: $("#loginLink, #registerLink") .click(function () { $('#loginLink').prop('disabled', true); $('#registerLink').prop('disabled', true); dialog(this); }); It calls the dialog correctly but doesn't disable the links and if I click the buttons more than once it calls up more than one dialog box. Is there something I am doing wrong? I can't see why it would not work.

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  • Dynamic model choice field in django formset using multiple select elements

    - by Aryeh Leib Taurog
    I posted this question on the django-users list, but haven't had a reply there yet. I have models that look something like this: class ProductGroup(models.Model): name = models.CharField(max_length=10, primary_key=True) def __unicode__(self): return self.name class ProductRun(models.Model): date = models.DateField(primary_key=True) def __unicode__(self): return self.date.isoformat() class CatalogItem(models.Model): cid = models.CharField(max_length=25, primary_key=True) group = models.ForeignKey(ProductGroup) run = models.ForeignKey(ProductRun) pnumber = models.IntegerField() def __unicode__(self): return self.cid class Meta: unique_together = ('group', 'run', 'pnumber') class Transaction(models.Model): timestamp = models.DateTimeField() user = models.ForeignKey(User) item = models.ForeignKey(CatalogItem) quantity = models.IntegerField() price = models.FloatField() Let's say there are about 10 ProductGroups and 10-20 relevant ProductRuns at any given time. Each group has 20-200 distinct product numbers (pnumber), so there are at least a few thousand CatalogItems. I am working on formsets for the Transaction model. Instead of a single select menu with the several thousand CatalogItems for the ForeignKey field, I want to substitute three drop-down menus, for group, run, and pnumber, which uniquely identify the CatalogItem. I'd also like to limit the choices in the second two drop-downs to those runs and pnumbers which are available for the currently selected product group (I can update them via AJAX if the user changes the product group, but it's important that the initial page load as described without relying on AJAX). What's the best way to do this? As a point of departure, here's what I've tried/considered so far: My first approach was to exclude the item foreign key field from the form, add the substitute dropdowns by overriding the add_fields method of the formset, and then extract the data and populate the fields manually on the model instances before saving them. It's straightforward and pretty simple, but it's not very reusable and I don't think it is the right way to do this. My second approach was to create a new field which inherits both MultiValueField and ModelChoiceField, and a corresponding MultiWidget subclass. This seems like the right approach. As Malcolm Tredinnick put it in a django-users discussion, "the 'smarts' of a field lie in the Field class." The problem I'm having is when/where to fetch the lists of choices from the db. The code I have now does it in the Field's __init__, but that means I have to know which ProductGroup I'm dealing with before I can even define the Form class, since I have to instantiate the Field when I define the form. So I have a factory function which I call at the last minute from my view--after I know what CatalogItems I have and which product group they're in--to create form/formset classes and instantiate them. It works, but I wonder if there's a better way. After all, the field should be able to determine the correct choices much later on, once it knows its current value. Another problem is that my implementation limits the entire formset to transactions relating to (CatalogItems from) a single ProductGroup. A third possibility I'm entertaining is to put it all in the Widget class. Once I have the related model instance, or the cid, or whatever the widget is given, I can get the ProductGroup and construct the drop-downs. This would solve the issues with my second approach, but doesn't seem like the right approach.

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