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  • weird behavior with acts_as_taggable_on

    - by macek
    For some reason, tags aren't showing up on a taggable object when an tagger is specified. testing the post class Post < ActiveRecord::Base acts_as_taggable_on :tags belongs_to :user end >> p = Post.first => #<Post id: 1, ...> >> p.is_taggable? => true >> p.tag_list = "foo, bar" => "foo, bar" >> p.save => true >> p.tags => [#<Tag id: 1, name: "foo">, #<Tag id: 2, name: "bar">] testing the user class User < ActiveRecord::Base acts_as_tagger has_many :posts end >> u = User.first => #<User id: 1, ...> >> u.is_tagger? => true >> u.tag(p, :with => "hello, world", :on => :tags) => true >> u.owned_tags => [#<Tag id: 3, name: "hello">, #<Tag id: 4, name: "world">] refresh the post >> p = Post.first => #<Post id: 1 ...> >> p.tags => [#<Tag id: 2, name: "bar">, #<Tag id: 1, name: "foo">] Where's the hello and world tags? Miraculously, if I modify the database directly to set tagger_id and tagger_type to NULL, the two missing tags will show up. I suspect there's something wrong with my User model? What gives?

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  • How can UISearchDisplayController autorelease cause crash in a different view controller?

    - by Tofrizer
    Hi, I have two view controllers A and B. From A, I navigate to view controller B as follows: // in View Controller A // navigateToB method -(void) navigateToB { BViewController *bViewController = [[BViewController alloc] initWithNibName: @"BView" bundle:nil]; bViewController.bProperty1 = SOME_STRING_CONSTANT; bViewController.title = @"A TITLE OF A VC's CHOOSING"; [self.navigationController pushViewController: bViewController animated:YES]; [bViewController release]; //<----- releasing 0x406c1e0 } In BViewController, the property bPropery1 is defined with copy as below (note, B also contains UITableView and other properties): @property (nonatomic, copy) NSString *bProperty1; Everything appeared to work fine when navigating back and forth between A and B. That is until I added a UISearchDisplayController to the table view contained in BViewController. Now when I navigate out of B, back to A, the app crashes. Stack trace shows what looks the search display controller being autoreleased at time of crash: #0 0x009663a7 in ___forwarding___ #1 0x009426c2 in __forwarding_prep_0___ #2 0x018c8539 in -[UISearchDisplayController _destroyManagedTableView] #3 0x018c8ea4 in -[UISearchDisplayController dealloc] #4 0x00285ce5 in NSPopAutoreleasePool NSZombies shows: -[BViewController respondsToSelector:]: message sent to deallocated instance 0x406c1e0 And malloc history on this points to the bViewController already released in A's navigateToB method above: Call [2] [arg=132]: thread_a065e720 |start ... <snip> ..._sendActionsForEvents:withEvent:] | -[UIControl sendAction:to:forEvent:] | - [UIApplication sendAction:to:from:forEvent:] | -[**AViewController navigateToB**] | +[NSObject alloc] | +[NSObject allocWithZone:] | _internal_class_createInstance | _internal_class_createInstanceFromZone | calloc | malloc_zone_calloc Can someone please give me any ideas on what is happening here? In navigateToB method, once the bViewController is released (after pushViewController), that's should be it for bViewController. Nothing else even knows about it as it is local to the navigateToB method block and it has been released. When navigating from B back to A, nothing is invoked in viewDidLoad, viewWillAppear etc that will re-enter navigateToB. It looks like somehow search display controller has a reference to something in my AViewController and so as it is autoreleased it is taking this "something" down with it but I cannot understand how this is possible, especially as I'm using copy to pass data between A and B. I'm going potty over this. I'm sure this is my mistake somewhere and so I turn to you, Stack Overflow legends for any words of wisdom or advice on how to resolve this. Many Thanks.

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  • Visual Stuido debug problem

    - by cagin
    Hi there, I have a web application. I am developing on Visual Studio 2008. I want to debug my codes and i m putting a break point on page load event of my master page. But V.S doesnt stop on break point line when the project runnging first. But when i change a dropdownlist's item, V.S stop on break point line. I need to see some values at first loading. I dont know what can i do. Thanks for your help

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  • Jquery Automatic Image Slider w/ CSS & jQuery

    - by Jacinto
    This is Automatic Image Slider w/ CSS & jQuery by Soh Tanaka I am trying to customize it to show .desc when the mouse hover overs the slider but it does not seem to work any help? //Set Default State of each portfolio piece $(".paging").show(); $(".paging a:first").addClass("active"); //Get size of images, how many there are, then determin the size of the image reel. var imageWidth = $(".window").width(); var imageSum = $(".image_reel ul.examples").size(); var imageReelWidth = imageWidth * imageSum; //Adjust the image reel to its new size $(".image_reel").css({'width' : imageReelWidth}); //Paging + Slider Function rotate = function(){ var triggerID = $active.attr("rel") - 1; //Get number of times to slide var image_reelPosition = triggerID * imageWidth; //Determines the distance the image reel needs to slide $(".paging a").removeClass('active'); //Remove all active class $active.addClass('active'); //Add active class (the $active is declared in the rotateSwitch function) //Slider Animation $(".image_reel").animate({ left: -image_reelPosition }, 500 ); }; //Rotation + Timing Event rotateSwitch = function(){ play = setInterval(function(){ //Set timer - this will repeat itself every 3 seconds $active = $('.paging a.active').next(); if ( $active.length === 0) { //If paging reaches the end... $active = $('.paging a:first'); //go back to first } rotate(); //Trigger the paging and slider function }, 7000); //Timer speed in milliseconds (3 seconds) }; rotateSwitch(); //Run function on launch //On Hover $(".image_reel").hover(function() { clearInterval(play); //Stop the rotation }, function() { rotateSwitch(); //Resume rotation }); //Hide the tooglebox when page load $(".desc").hide(); //slide up and down when hover over heading 2 $(".image_reel").hover(function(){ // slide toggle effect set to slow you can set it to fast too. $(this).next(".desc").slideToggle("slow"); return true; }); //On Click $(".paging a").click(function() { $active = $(this); //Activate the clicked paging //Reset Timer clearInterval(play); //Stop the rotation rotate(); //Trigger rotation immediately rotateSwitch(); // Resume rotation return false; //Prevent browser jump to link anchor });

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  • Hiding Table Rows

    - by David Stein
    I have a table that I'm using to show details from the line items of a quote. I want to hide a particular row depending on the value of the field in it. The expression I've tried is to set the row visibility to: =IIF(isnothing(First(Fields!NEW_PRICEBREAKS.Value, "QuoteDetail")),true,false) When I run the query from the dataset "Null" returns for NEW_PRICEBREAKS for most of the records. Also, when I expanded the row with another column with this expression: =IIF(isnothing(First(Fields!NEW_PRICEBREAKS.Value, "QuoteDetail")),"is nothing","not nothing") I see "not nothing" repeated over and over again. I've attempted to use TRIM inside of the isnothing to remove spaces and it still doesn't work. Also, the sql data type for NEW_PRICEBREAKS is nvarchar(MAX). Any ideas how I can suppress this row correctly?

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  • Dereferencing pointers without pointing them at a variable

    - by Miguel
    I'm having trouble understanding how some pointers work. I always thought that when you created a pointer variable (p), you couldn't deference and assign (*p = value) unless you either malloc'd space for it (p = malloc(x)), or set it to the address of another variable (p = &a) However in this code, the first assignment works consistently, while the last one causes a segfault: typedef struct { int value; } test_struct; int main(void) { //This works int* colin; *colin = 5; //This never works test_struct* carter; carter->value = 5; } Why does the first one work when colin isn't pointing at any spare memory? And why does the 2nd never work? I'm writing this in C, but people with C++ knowledge should be able to answer this as well.

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  • Interspire to Magento migration

    - by patrikas
    Hello, I recently started with Magento and decided to migrate Interspire shopping cart I already made time ago to it. At first look Magento seems a very huge beast - lots of options, maybe lack of simplicity resulting in some performance loss. I've got user guide from which I am not getting much of benefit since there're just descriptions of very ordinary tasks that I could easily discover myself by poking around frontend/backend. So my first tasks are category and product export. Interspire seems to be exporting ONLY products in three available formats: Default MYOB Peachtree accounting I did some searching on Magento's product importing and found a blog post which says that I should create a few sample products with all the necessary attributes myself and then start the import. But what should I do with categories ? Is it possible to import them or instruct Magento to automatically create categories when importing product file if unknown category is encountered ? Thanks

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  • XSL unique values per node

    - by Nathan
    ok i have this xml <roots> <root> <name>first</name> <item type='test'><something>A</something></item> <item type='test'><something>B</something></item> <item type='test'><something>C</something></item> <item type='test'><something>A</something></item> <item type='other'><something>A</something></item> <item type='test'><something>B</something></item> <item type='other'><something>D</something></item> </root> <root> <name>second</name> <item type='test'><something>E</something></item> <item type='test'><something>B</something></item> <item type='test'><something>F</something></item> <item type='test'><something>A</something></item> <item type='other'><something>A</something></item> <item type='test'><something>B</something></item> <item type='other'><something>D</something></item> </root> </roots> now i need to get the unique values of each root node so far i have <?xml version="1.0" encoding="ISO-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output indent="yes" method="text"/> <xsl:key name="item-by-value" match="something" use="."/> <xsl:key name="rootkey" match="root" use="name"/> <xsl:template match="/"> <xsl:for-each select="key('rootkey','second')"> <xsl:for-each select="item/something"> <xsl:if test="generate-id() = generate-id(key('item-by-value', normalize-space(.)))"> <xsl:value-of select="."/> </xsl:if> </xsl:for-each> </xsl:for-each> </xsl:template> </xsl:stylesheet> if i use "First" as the key to get only the first root i get a good result ABCD how ever if i use "second" i only get EF but i need the result to be ABDFE

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  • comparing csv files

    - by Surresh2121
    I want to write a shell script to compare two .csv files. First one contains filename,path the second .csv file contains filename,paht,target. Now, I want to compare the two .csv files and output the target name where the file from the first .csv exists in the second .csv file. Ex. a.csv build.xml,/home/build/NUOP/project1 eesX.java,/home/build/adm/acl b.csv build.xml,/home/build/NUOP/project1,M1 eesX.java,/home/build/adm/acl,M2 ddexse3.htm,/home/class/adm/33eFg I want the output to be something like this. M1 and M2 Please help Thanks,

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  • Entity Framework Performance Problem

    - by Steve Horn
    I'm hoping that someone can help me understand how to overcome a performance problem I'm running into with the latest version of the Entity Framework. In my test, I created my model from a database consisting of around 80 tables. The problem that I'm running into is that the cost of the very first query I run on a thread is very expensive. If I run without pre-compiling views the first query takes anywhere from 5800 to 6600 milliseconds. If I pre-compile the views (see this article) I can get the initial query cost down to about 2800 to 3200 milliseconds. 3 seconds for each request is still unacceptable for my needs. Subsequent queries are very fast. Can you please help me understand how to eliminate the poor performance of the initial query? I'm using the version of entity framework that ships with Visual Studio 2010 RC.

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  • Writing annotataion schemas for Callisto

    - by Ken Bloom
    Does anybody know where I can find documentation on how to write annotation schemas for Callisto? I'm looking to write something a little more complicated than I can generate from a DTD -- that only gives me the ability to tag different kinds of text mentions. I'm looking to create a schema that represents a single type of relationship between five or six different kinds of textual mentions (and some of these types of mentions have attributes that I need to assign values to), and possibly having a second type of relationship between the first two instances of the first type of relationship. (Alternatively, does anybody know of any software that would be better for this kind of schema? I've been looking at WordFreak, but it's a little clumsy, and it doesn't support attributes on its textual mentions.)

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  • How do I escape ampersands in batch files?

    - by Peter Mortensen
    How do I escape ampersands in a batch file (or from the Windows command line) in order to use the start command to open web pages with ampersands in the URL? Double quotes will not work with start; this starts a new command line window instead. Update 1: Wael Dalloul's solution works. In addition, if there are URL encoded characters (e.g. space is encoded as %20) in the URL and it is in a batch file then '%' must be encoded as '%%'. This is not the case in the example. Example, from the command line (CMD.EXE): start http://www.google.com/search?client=opera&rls=en&q=escape+ampersand&sourceid=opera&ie=utf-8&oe=utf-8 will result in http://www.google.com/search?client=opera being opened in the default browser and these errors in the command line window: 'rls' is not recognized as an internal or external command, operable program or batch file. 'q' is not recognized as an internal or external command, operable program or batch file. 'sourceid' is not recognized as an internal or external command, operable program or batch file. 'ie' is not recognized as an internal or external command, operable program or batch file. 'oe' is not recognized as an internal or external command, operable program or batch file. Platform: Windows XP 64 bit SP2.

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  • Custom array sort in perl

    - by ABach
    I have a perl array of to-do tasks that looks like this: @todos = ( "1 (A) Complete online final @evm4700 t:2010-06-02", "3 Write thank-you t:2010-06-10", "4 (B) Clean t:2010-05-30", "5 Donate to LSF t:2010-06-02", "6 (A) t:2010-05-30 Pick up dry cleaning", "2 (C) Call Chris Johnson t:2010-06-01" ); That first number is the task's ID. If a task has ([A-Z]) next to, that defines the task's priority. What I want to do is sort the tasks array in a way that places the prioritized items first (and in order): @todos = ( "1 (A) Complete online final @evm4700 t:2010-06-02", "6 (A) t:2010-05-30 Pick up dry cleaning", "4 (B) Clean t:2010-05-30", "2 (C) Call Chris Johnson t:2010-06-01" "3 Write thank-you t:2010-06-10", "5 Donate to LSF t:2010-06-02", ); I cannot use a regular sort() because of those IDs next to the tasks, so I'm assuming that some sort of customized sorting subroutine is needed. However, my knowledge of how to do this efficiently in perl is minimal. Thanks, all.

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  • How do you keep the text selection on a DataGridView?

    - by fneep
    I'm running C# 2.0, and I've written an application with a DataGridView in virtualmode and a TreeView in the same form, but in different panels of a SplitContainer. My application has a "find all" function that finds all instances of a certain string, and adds them as the child nodes to a new node to the TreeView (it's a tree view because you can have multiple search results by having different root nodes). That idea is that when you click on one of those search results in the TreeView, that it would select the specific text of that result in the DataGridView (Virtually the same as Notepad++'s find all function) When I click on the TreeView, it does set the selected cell of the DataGridView and highlight the specific text, but it loses that specific text selection instantly (but keeps the cell selection) because by clicking on the TreeView the DataGridView loses focus. Here's the code for the AfterSelect of the TreeView: private void Tree_Results_AfterSelect(object sender, TreeViewEventArgs e) { if (e.Node.Level > 0) { SearchResult SelectedItem = (SearchResult)Tree_Results.SelectedNode.Tag; DataViewMain.CurrentCell = DataViewMain[SelectedItem.TypeIndex, SelectedItem.LineIndex]; DataViewMain.BeginEdit(false); DataGridViewTextBoxEditingControl SelectionData = (DataGridViewTextBoxEditingControl)DataViewMain.EditingControl; SelectionData.SelectionStart = SelectedItem.HighlightStart; SelectionData.SelectionLength = SelectedItem.HightlightLength; } } If the DataGridView were a text box I could possibly set HideSelection to false, but DataGridViews have no such property (and changing the Hide Selection for the EditingControl does nothing) Any ideas? I'm receptive to a different control instead of a TreeView that would allow my DataGridView to retain focus.

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  • Question about spring manning-in-action

    - by Gandalf StormCrow
    I saw people asking about best book for learning spring, and I came across manning.spring in action was recommended most of the time so I decided to give it a go. The thing is the author offers some pretty reasonable explanations, puzzle by puzzle it gets in your head, than you just need to code it and you're done, you get it(this is how I work don't know about the others). When it comes to the code its very disapointing, I went trought the Knight example like 2 or 3 times by now and I see its incorrect in the book, I mean its hard already for people eager to learn and why not a note somewhere in the book like pseudo-code or something. The knight example in the first chapter is missing two classes QuestFailedException and HolyGrail I mean other people must have noticed this, why is everyone recommending this book without saying at least it has some errors(like many others do), was anyone actually been able to compile and this first chapter example?

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  • Filter elements in PropertyGrid

    - by serhio
    In System.Windows.Forms there are a PropertyGrid that displays properties of an attached object. Let's say MyTextBox : TextBox. Now, I would like to display on it some MyTextBox properties, say only Size, Location and my custom property Date. More that than, I would like to be able to change the real property names, say "Dimension", "Location" and "Starting Date". I saw two projects on this subject : first and second, but first does not work well(for browsable properties), and the second seems to add an event for each property changes, this is not acceptable.

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  • Why is the same input returning two different MD5 hashes?

    - by Rob
    Alright, I have two files. They are the EXACT SAME. The first file is: http://iadsonline.com/servconfig.php And the second file is: http://xzerox.info/servconfig.php However, when I use md5_file() to get their MD5, They return two different MD5's. The first returns cc7819055cde3194bb3b136bad5cf58d, which is incorrect, and the second returns 96a0cec80eb773687ca28840ecc67ca1, which is correct. The file is simply an &nbsp; To verify, I've used this code: $contents = file_get_contents($URL); echo htmlentities($contents); And they both return &nbsp; So why is it hashing them differently?

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  • Ruby on Rails Join Table Associations

    - by Eef
    Hey, I have a Ruby on Rails application setup like so: User Model has_and_belongs_to_many :roles Role Model has_many :transactions has_and_belongs_to_many :users Transaction Model belongs_to :role This means that a join table is used called roles_users and it also means that a user can only see the transactions that have been assigned to them through roles, usage example: user = User.find(1) transactions = user.roles.first.transactions This will return the transactions which are associated with the first role assigned to the user. If a user has 2 roles assigned to them, at the moment to get the transactions associated with the second role I would do: transactions = user.roles.last.transactions I am basically trying to figure out a way to setup an association so I can grab the user's transactions via something like this based on the roles defined in the association between the user and roles: user = User.find(1) transactions = user.transactions I am not sure if this is possible? I hope you understand what I am trying to do.

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  • Matching unmatched strings based on a unknown pattern

    - by Polity
    Alright guys, i really hurt my brain over this one and i'm curious if you guys can give me any pointers towards the right direction i should be taking. The situation is this: Lets say, i have a collection of strings (let it be clear that the pattern of this strings is unknown. For a fact, i can say that the string contain only signs from the ASCII table and therefore, i dont have to worry about weird Chinese signs). For this example, i take the following collection of strings (note that the strings dont have to make any human sence so dont try figguring them out :)): "[001].[FOO].[TEST] - 'foofoo.test'", "[002].[FOO].[TEST] - 'foofoo.test'", "[003].[FOO].[TEST] - 'foofoo.test'", "[001].[FOO].[TEST] - 'foofoo.test.sample'", "[002].[FOO].[TEST] - 'foofoo.test.sample'", "-001- BAR.[TEST] - 'bartest.xx1", "-002- BAR.[TEST] - 'bartest.xx1" Now, what i need to have is a way of finding logical groups (and subgroups) of these set of strings, so in the above example, just by rational thinking, you can combine the first 3, the 2 after that and the last 2. Also the resulting groups from the first 5 can be combined in one main group with 2 subgroups, this should give you something like this: { { "[001].[FOO].[TEST] - 'foofoo.test'", "[002].[FOO].[TEST] - 'foofoo.test'", "[003].[FOO].[TEST] - 'foofoo.test'", } { "[001].[FOO].[TEST] - 'foofoo.test.sample'", "[002].[FOO].[TEST] - 'foofoo.test.sample'", } { "-001- BAR.[TEST] - 'bartest.xx1", "-002- BAR.[TEST] - 'bartest.xx1" } } Sorry for the layout above but indenting with 4 spaces doesnt seem to work correctly (or im frakk'n it up). Anyways, I'm not sure how to approach this problem (how to get the result desired as indicated above). First of, i thought of creating a huge set of regexes which would parse most known patterns but the amount of different patterns is just to huge that this isn't realistic. Another think i thought of was parsing each indidual word within a string (so strip all non alphabetic or numeric characters and split by those), and if X% matches, i can assume the strings belong to the same group. (where X wil probably be around 80/90). However, i find the area of speculation kinda big. For example, when matching strings with each 20 words, the change of hitting above 80% is kinda big (that means that 4 words can differ), however when matching only 8 words, 2 words at most can differ. My question to you is, what would be a logical approach in the above situation? Thanks in advance!

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  • How does NameScope in WPF works ?

    - by Nicolas Dorier
    I'm having a strange behavior with NameScopes in WPF, I have created a CustomControl called FadingPopup which is a child class of Window with nothing special inside. <Window.Resources> <local:FadingPopup> <Button Name="prec" Content="ahah"></Button> <Button Content="{Binding ElementName=prec, Path=Content}"></Button> </local:FadingPopup> </Window.Resources> In this snippet, the binding doesn't work (always empty). If I move these buttons from the resources to the content of the window like this : <Window ...> <Button Name="prec" Content="ahah"></Button> <Button Content="{Binding ElementName=prec, Path=Content}"></Button> </Window> The binding works as expected. Now, I have tried a mix between these two snippets : <Window...> <Window.Resources> <local:FadingPopup> <Button Name="prec" Content="Haha"></Button> </local:FadingPopup> </Window.Resources> <Button Content="{Binding ElementName=prec, Path=Content}"></Button> </Window> It works as well. Apparently, if the button prec is in the resources it registers itself in the NameScope of the Window. BUT, it seems that the Binding tries to resolve ElementName with the NameScope of the FadingPopup (which is null), thus the binding doesn't work... My first snipped works well if I specify a NameScope in my class FadingPopup : static FadingPopup() { NameScope.NameScopeProperty.OverrideMetadata(typeof(FadingPopup), new PropertyMetadata(new NameScope())); } But I don't like this solution because I don't understand why, in the first snippet, prec is registered in the NameScope of Window, but ElementName is resolved with the NameScope of FadingGroup (which is null by default)... Does someone can explain to me what is going on ? Why my first snippet doesn't work, if I don't specify a default NameScope for FadingGroup ?

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  • Objective C Array and Object Release

    - by david
    Hi, I have a newbie question regarding when to release the elements of a NSArray. See following pseudo code: NSMutalbeArray *2DArray = [[NSMutableArray alloc] initWithCapacity:10]; for (int i=0;i<10;i++) { NSMutableArray *array = [[MSMutableArray alloc] initWithCapacity:5]; for (int j=0;j<5;j++) { MyObject *obj = [[MyObject alloc] init]; [array addObject:obj]; [obj release]; } [2DArray addObject:array]; [array release]; } // use 2DArray to do something [2DArray release] My question here is, when I release 2DArray, do I need to explicitly release each of its element (array) first? Also, before I release the "array" object, do I need to release each of its element (MyObject) first? I am new to Objective C. Please help. thanks.

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  • Select dynamic string has a different value when referenced in Where clause

    - by David
    I dynamically select a string built using another string. So, if string1='David Banner', then MyDynamicString should be 'DBanne' Select ... , Left( left((select top 1 strval from dbo.SPLIT(string1,' ')) //first word ,1) //first character + (select top 1 strval from dbo.SPLIT(string1,' ') //second word where strval not in (select top 1 strval from dbo.SPLIT(string1,' '))) ,6) //1st character of 1st word, followed by up to 5 characters of second word [MyDynamicString] ,... From table1 Join table2 on table1pkey=table2fkey Where MyDynamicString <> table2.someotherfield I know table2.someotherfield is not equal to the dynamic string. However, when I replace MyDynamicString in the Where clause with the full left(left(etc.. function, it works as expected. Can I not reference this string later in the query? Do I have to build it using the left(left(etc.. function each time in the where clause?

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  • writing 'remove' function in prolog

    - by Adrian
    I am desperately trying to create a remove function, that will simply remove all items that equal to X from a list. After many changes, this is my code so far: remove([], X, L1). /* when the source list is empty, stop*/ remove([X|T], X, L1) :- remove(T, X, L1). /* when first element in the list equals X, don't append it to L1 */ remove([H|T], X, L1) :- remove(T, X, [H|L1]). /*when first element in the list doesn't equal X, append it to L1 */ when running on remove([1,2,3,4,5], 3, R). it returns two trues and nothing else. Anyone has any idea what I'm doing wrong?

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  • Modelling boost::Lockable with semaphore rather than mutex (previously titled: Unlocking a mutex fr

    - by dan
    I'm using the C++ boost::thread library, which in my case means I'm using pthreads. Officially, a mutex must be unlocked from the same thread which locks it, and I want the effect of being able to lock in one thread and then unlock in another. There are many ways to accomplish this. One possibility would be to write a new mutex class which allows this behavior. For example: class inter_thread_mutex{ bool locked; boost::mutex mx; boost::condition_variable cv; public: void lock(){ boost::unique_lock<boost::mutex> lck(mx); while(locked) cv.wait(lck); locked=true; } void unlock(){ { boost::lock_guard<boost::mutex> lck(mx); if(!locked) error(); locked=false; } cv.notify_one(); } // bool try_lock(); void error(); etc. } I should point out that the above code doesn't guarantee FIFO access, since if one thread calls lock() while another calls unlock(), this first thread may acquire the lock ahead of other threads which are waiting. (Come to think of it, the boost::thread documentation doesn't appear to make any explicit scheduling guarantees for either mutexes or condition variables). But let's just ignore that (and any other bugs) for now. My question is, if I decide to go this route, would I be able to use such a mutex as a model for the boost Lockable concept. For example, would anything go wrong if I use a boost::unique_lock< inter_thread_mutex for RAII-style access, and then pass this lock to boost::condition_variable_any.wait(), etc. On one hand I don't see why not. On the other hand, "I don't see why not" is usually a very bad way of determining whether something will work. The reason I ask is that if it turns out that I have to write wrapper classes for RAII locks and condition variables and whatever else, then I'd rather just find some other way to achieve the same effect. EDIT: The kind of behavior I want is basically as follows. I have an object, and it needs to be locked whenever it is modified. I want to lock the object from one thread, and do some work on it. Then I want to keep the object locked while I tell another worker thread to complete the work. So the first thread can go on and do something else while the worker thread finishes up. When the worker thread gets done, it unlocks the mutex. And I want the transition to be seemless so nobody else can get the mutex lock in between when thread 1 starts the work and thread 2 completes it. Something like inter_thread_mutex seems like it would work, and it would also allow the program to interact with it as if it were an ordinary mutex. So it seems like a clean solution. If there's a better solution, I'd be happy to hear that also. EDIT AGAIN: The reason I need locks to begin with is that there are multiple master threads, and the locks are there to prevent them from accessing shared objects concurrently in invalid ways. So the code already uses loop-level lock-free sequencing of operations at the master thread level. Also, in the original implementation, there were no worker threads, and the mutexes were ordinary kosher mutexes. The inter_thread_thingy came up as an optimization, primarily to improve response time. In many cases, it was sufficient to guarantee that the "first part" of operation A, occurs before the "first part" of operation B. As a dumb example, say I punch object 1 and give it a black eye. Then I tell object 1 to change it's internal structure to reflect all the tissue damage. I don't want to wait around for the tissue damage before I move on to punch object 2. However, I do want the tissue damage to occur as part of the same operation; for example, in the interim, I don't want any other thread to reconfigure the object in such a way that would make tissue damage an invalid operation. (yes, this example is imperfect in many ways, and no I'm not working on a game) So we made the change to a model where ownership of an object can be passed to a worker thread to complete an operation, and it actually works quite nicely; each master thread is able to get a lot more operations done because it doesn't need to wait for them all to complete. And, since the event sequencing at the master thread level is still loop-based, it is easy to write high-level master-thread operations, as they can be based on the assumption that an operation is complete when the corresponding function call returns. Finally, I thought it would be nice to use inter_thread mutex/semaphore thingies using RAII with boost locks to encapsulate the necessary synchronization that is required to make the whole thing work.

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  • Looping through JSON arrays

    - by George
    I'm trying to pull the field names in the header of some JSON output. The following is a sample of the JSON header info: {"HEADER":{"company":{"label":"Company Name"},"streetaddress":{"label":"Street Address"},"ceo":{"label":"CEO Name","fields":{"firstname":{"label":"First Name"},"lastname":{"label":"Last Name"}}} I'm able to loop through the header and output the field and label (i.e. company and Company Name) using the following code: obj = JSON.parse(jsonResponse); for (var key in obj.HEADER) { response.write ( obj.HEADER[key].label ); response.write ( key ); } but can't figure out how to loop through and output the sub array of fields (i.e. firstname and First Name). Any ideas?

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