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  • Getting field of type bytea in helper table when using GenerationType.IDENTITY

    - by dtrunk
    I'm creating my db scheme using Hibernate. There's a Table called "tbl_articles" and another one called "tbl_categories". To have a n-n relationship a helper table ("tbl_articles_categories") is needed. Here are all necessary Entities: @Entity @Table( name = "tbl_articles" ) public class Article implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( strategy = GenerationType.IDENTITY ) private Integer id; // other fields... public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } // other fields... } @Entity @Table( name = "tbl_categories" ) public class Category implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( strategy = GenerationType.IDENTITY ) private Integer id; // other fields public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } // other fields... } @Entity @Table( name = "tbl_articles_categories" ) @AssociationOverrides({ @AssociationOverride( name = "pk.article", joinColumns = @JoinColumn( name = "article_id" ) ), @AssociationOverride( name = "pk.category", joinColumns = @JoinColumn( name = "category_id" ) ) }) public class ArticleCategory { private ArticleCategoryPK pk = new ArticleCategoryPK(); public void setPk( ArticleCategoryPK pk ) { this.pk = pk; } @EmbeddedId public ArticleCategoryPK getPk() { return pk; } @Transient public Article getArticle() { return pk.getArticle(); } public void setArticle( Article article ) { pk.setArticle( article ); } @Transient public Category getCategory() { return pk.getCategory(); } public void setCategory( Category category ) { pk.setCategory( category ); } } @Embeddable public class ArticleCategoryPK implements Serializable { private static final long serialVersionUID = 1L; @ManyToOne @ForeignKey( name = "tbl_articles_categories_fkey_article_id" ) private Article article; @ManyToOne @ForeignKey( name = "tbl_articles_categories_fkey_category_id" ) private Category category; public ArticleCategoryPK( Article article, Category category ) { setArticle( article ); setCategory( category ); } public ArticleCategoryPK() { } public Article getArticle() { return article; } public void setArticle( Article article ) { this.article = article; } public Category getCategory() { return category; } public void setCategory( Category category ) { this.category = category; } } Now, I'm getting a serial type what I wanted in my articles table as well as in my categories table. But looking into my helper table, there aren't the expected fields article_id and category_id each of type integer - instead there are article and category of type bytea. What's wrong here? EDIT: Sorry, forgot to mention that I'm using PostgreSQL.

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  • How can I get rid of the resize-handle in a QDialog?

    - by Georg
    I've got the following class: class SelectDateDialog(QDialog): startDate = date.today() endDate = date.today() def __init__(self, text, isInterval = False): QDialog.__init__(self) uic.loadUi("resources/SelectDate.ui", self) Now, the dialog is resizable on Mac OS X 10.5, but it shouldn't be. It has the resize-handle in the lower right corner. I've already tried the setSizeGripEnabled function, it didn't change anything. How can I make it not resizable?

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  • Unexpected tag T_ECHO in inline if

    - by Lombo
    I have something like this in one of my views <li <?php $isCurrent ? echo 'class="current"' : ''?> > <a href="SOME_LINK" class="SOME_CLASS">SOME_TEXT</a> </li> This causes a syntax error, unexpected T_ECHO. Changing echo for print solves the issue, but I would like to understand why I cannot use echo.

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  • PHP: Extending static member arrays

    - by tstenner
    I'm having the following scenario: class A { public static $arr=array(1,2); } class B extends A { public static $arr=array(3,4); } Is there any way to combine these 2 arrays so B::$arr is 1,2,3,4? I don't need to alter these arrays, but I can't declare them als const, as PHP doesn't allow const arrays.http://stackoverflow.com/questions/ask The PHP manual states, that I can only assign strings and constants, so parent::$arr + array(1,2) won't work, but I think it should be possible to do this.

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  • Error CS0103: The name 'Class1' does not exist in the current context

    - by Mad coder.
    In my website I created a class e.g. Class1.cs in App_Code folder when I am trying to load default page which is using this Class file I am getting the following error CS0103: The name 'Class1' does not exist in the current context for the code String something = Class1.item1(text1.Text, text2.Text); and Class1.cs consists of protected static string item1(string a, string b) { //some action here return null; } Everything works fine in my VS2010 but when I host the website in my server I am getting this issue.

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  • javascript undefined compare

    - by nahum
    Ok here is my question in javascript you can declare a variable and be undefined you can apply variable == undefined, I know that but how you can compare a value that you dont know yet if it's in the cpu memory. I have a class which is create it when the user click on a button. before this the class is undefined there no exist in any where so how can I compare it? without using try{}catch(e){} is there a way????

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  • dynamically bound elements don't subscribe to CSS rules

    - by user961627
    I'm using ajax to dynamically populate a menu. The problem is the dynamically created elements do not follow the CSS rules, although they're created with the right classname. This is surprising. Here's my HTML: <div id='menu1'> <ul class='menu'> <?php $sql = /// /* some sql string, which works */ $result = mysql_query($sql); while($row = mysql_fetch_array( $result )) { $prod_id = $row['product_id']; $prod_name = $row['product_name']; echo "<li data-title='$prod_id' class='menu1_item'>".$prod_name."</li> "; } ?> </ul> </div> <div id='menu2'> <ul class='menu'> </ul> </div> <div id='menu3'> <ul class='menu'> </ul> </div> Here's my jquery: $(".menu1_item").click( function() { $.ajax({ type: "POST", data: { m: '2', id: $(this).attr('data-title') }, url: "fetch_designs.php", success: function(msg){ if (msg != ''){ $("#menu2").html(msg).show(); $(".menu2_item").bind('click',function() { $.ajax({ type: "POST", data: { m: '3', id: $(this).attr('data-title') }, url: "fetch_designs.php", success: function(msg){ if (msg != ''){ $("#menu3").html(msg).show(); } } }); //end menu2 click }); //end if } //end success } }); //end menu1 click }); My CSS is as follows: ul.menu li { cursor:pointer; list-style: none; } #menu1, #menu2, #menu3 { margin:50px; position:relative; display:block; float:left; } .menu1-item .menu2-item .menu3-item { padding:4px; background-color:lightgray; color:black; cursor:pointer; }

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  • Require a default constructor in java?

    - by jdc0589
    Is there any way to require that a class have a default (no parameter) constructor, aside from using a reflection check like the following? (the following would work, but it's hacky and reflection is slow) boolean valid = false; for(Constructor<?> c : TParse.class.getConstructors()) { if(c.getParameterTypes().length == 0) { valid = true; break; } } if(!valid) throw new MissingDefaultConstructorException(...);

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  • Compiling servlets for tomcat

    - by L4N0
    Hello I am trying to modify one of the default files that comes with tomcat SessionExample.java, and trying to compile it but I get an error. javac -classpath "E:\Program Files\Apache Software Foundation\Apache Tomcat 6.0.18\lib\servlet-api.jar" SessionExample.java Gives me this error SessionExample.java:26: package util does not exist import util.HTMLFilter; ^ SessionExample.java:90: cannot find symbol symbol : variable HTMLFilter location: class SessionExample out.println(HTMLFilter.filter(name) + " = " ^ SessionExample.java:91: cannot find symbol symbol : variable HTMLFilter location: class SessionExample + HTMLFilter.filter(value) + ""); ^ 3 errors Thank you

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  • How to decode "application/x-qabstractitemmodeldatalist" in Qt for drag and drop?

    - by gct
    I've created a child class of QTreeWidget that I want to be able to drag items from another tree widget too (I want to handle the insertion myself though), as well as from a QListWidget. I've overridden the dropEvent method in my class, and it looks like the mimetype of the data I'm getting from my QTreeWidget is application/x-qabstractitemmodeldatalist, how can I decode this to get the items from the tree back out?

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  • How to use becomes in Rails.

    - by alokswain
    I have a Post Class and a Comment Class. I have a post object and want to convert it to a Comment object. I went through Rails api and found becomes(klass).For now there is not association between a Post and Comment. So i tried @post.becomes(Comment). but becomes method could not be found for @post object. Am i missing something ?

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  • when does static member gets memory.

    - by vaibhav
    I have a class which have a static member. As I understand all static members are common for all instance of the class. So it means static members would get memory only once. Where is this memory is allocated (Stack or Heap) and when this memory get allocated.

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  • How can I convert a C# application that uses StandardInput and StandardOutput in .NET Compact Framew

    - by Chad
    I have an application that uses the Process class, StandardInput, and StandardOutput to communicate with an external executable. I am using this to pass strings back and forth, and it works well in my Windows application. On the mobile device, I do not see StandardInput or StandardOutput in the Process class. Is there an easy way to replicate this functionality on the Mobile?

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  • Unit testing installation of services

    - by skiphoppy
    Our installer program is going to be installing a number of system services, under both Windows and UNIX, using JavaServiceWrapper. There will be a class responsible for creating JavaServiceWrapper config files, installing the services, etc. Can I have some suggestions on how to unit-test this class?

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  • How do I do distributed UML development (à la FOSS)?

    - by James A. Rosen
    I have a UML project (built in IBM's Rational System Architect/Modeler, so stored in their XML format) that has grown quite large. Additionally, it now contains several pieces that other groups would like to re-use. I come from a software development (especially FOSS) background, and am trying to understand how to use that as an analogy here. The problem I am grappling with is similar to the Fragile Base Class problem. Let me start with how it works in an object-oriented (say, Java or Ruby) FOSS ecosystem: Group 1 publishes some "core" package, say "net/smtp version 1.0" Group 2 includes Group 1's net/smtp 1.0 package in the vendor library of their software project At some point, Group 1 creates a new 2.0 branch of net/smtp that breaks backwards compatibility (say, it removes an old class or method, or moves a class from one package to another). They tell users of the 1.0 version that it will be deprecated in one year. Group 2, when they have the time, updates to net/smtp 2.0. When they drop in the new package, their compiler (or test suite, for Ruby) tells them about the incompatibility. They do have to make some manual changes, but all of the changes are in the code, in plain text, a medium with which they are quite familiar. Plus, they can often use their IDE's (or text editor's) "global-search-and-replace" function once they figure out what the fixes are. When we try to apply this model to UML in RSA, we run into some problems. RSA supports some fairly powerful refactorings, but they seem to only work if you have write access to all of the pieces. If I rename a class in one package, RSA can rename the references, but only at the same time. It's very difficult to look at the underlying source (the XML) and figure out what's broken. To fix such a problem in the RSA editor itself means tons of clicking on things -- there is no good equivalent of "global-search-and-replace," at least not after an incomplete refactor. They real sticking point seems to be that RSA assumes that you want to do all your editing using their GUI, but that makes certain operations prohibitively difficult. Does anyone have examples of open-source UML projects that have overcome this problem? What strategies do they use for communicating changes?

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  • WP7 databinding displays int but not string?

    - by user1794106
    Whenever I test my app.. it binds the data from Note class and displays it if it isn't a string. But for the string variables it wont bind. What am I doing wrong? Inside my main: <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"> <ListBox x:Name="Listbox" SelectionChanged="listbox_SelectionChanged" ItemsSource="{Binding}"> <ListBox.ItemTemplate> <DataTemplate> <Border Width="800" MinHeight="60"> <StackPanel> <TextBlock x:Name="Title" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Name}"/> <TextBlock x:Name="Date" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Modified}"/> </StackPanel> </Border> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Grid> </Grid> in code behind: protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e) { MessageBox.Show("enters onNav Main"); DataContext = null; DataContext = Settings.NotesList; Settings.CurrentNoteIndex = -1; Listbox.SelectedIndex = -1; if (Settings.NotesList != null) { if (Settings.NotesList.Count == 0) { Notes.Text = "No Notes"; } else { Notes.Text = ""; } } } and public static class Settings { public static ObservableCollection<Note> NotesList; static IsolatedStorageSettings settings; private static int currentNoteIndex; static Settings() { NotesList = new ObservableCollection<Note>(); settings = IsolatedStorageSettings.ApplicationSettings; MessageBox.Show("enters constructor settings"); } notes class: public class Note { public DateTimeOffset Modified { get; set; } public string Title { get; set; } public string Content { get; set; } public int TextSize { get; set; } public Note() { MessageBox.Show("enters Note Constructor"); Modified = DateTimeOffset.Now; Title = "test"; Content = "test"; TextSize = 32; } }

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  • Trappings MySQL Warnings on Calls Wrapped in Classes -- Python

    - by chernevik
    I can't get Python's try/else blocks to catch MySQL warnings when the execution statements are wrapped in classes. I have a class that has as a MySQL connection object as an attribute, a MySQL cursor object as another, and a method that run queries through that cursor object. The cursor is itself wrapped in a class. These seem to run queries properly, but the MySQL warnings they generate are not caught as exceptions in a try/else block. Why don't the try/else blocks catch the warnings? How would I revise the classes or method calls to catch the warnings? Also, I've looked through the prominent sources and can't find a discussion that helps me understand this. I'd appreciate any reference that explains this. Please see code below. Apologies for verbosity, I'm newbie. #!/usr/bin/python import MySQLdb import sys import copy sys.path.append('../../config') import credentials as c # local module with dbase connection credentials #============================================================================= # CLASSES #------------------------------------------------------------------------ class dbMySQL_Connection: def __init__(self, db_server, db_user, db_passwd): self.conn = MySQLdb.connect(db_server, db_user, db_passwd) def getCursor(self, dict_flag=True): self.dbMySQL_Cursor = dbMySQL_Cursor(self.conn, dict_flag) return self.dbMySQL_Cursor def runQuery(self, qryStr, dict_flag=True): qry_res = runQueryNoCursor(qryStr=qryStr, \ conn=self, \ dict_flag=dict_flag) return qry_res #------------------------------------------------------------------------ class dbMySQL_Cursor: def __init__(self, conn, dict_flag=True): if dict_flag: dbMySQL_Cursor = conn.cursor(MySQLdb.cursors.DictCursor) else: dbMySQL_Cursor = conn.cursor() self.dbMySQL_Cursor = dbMySQL_Cursor def closeCursor(self): self.dbMySQL_Cursor.close() #============================================================================= # QUERY FUNCTIONS #------------------------------------------------------------------------------ def runQueryNoCursor(qryStr, conn, dict_flag=True): dbMySQL_Cursor = conn.getCursor(dict_flag) qry_res =runQueryFnc(qryStr, dbMySQL_Cursor.dbMySQL_Cursor) dbMySQL_Cursor.closeCursor() return qry_res #------------------------------------------------------------------------------ def runQueryFnc(qryStr, dbMySQL_Cursor): qry_res = {} qry_res['rows'] = dbMySQL_Cursor.execute(qryStr) qry_res['result'] = copy.deepcopy(dbMySQL_Cursor.fetchall()) qry_res['messages'] = copy.deepcopy(dbMySQL_Cursor.messages) qry_res['query_str'] = qryStr return qry_res #============================================================================= # USAGES qry = 'DROP DATABASE IF EXISTS database_of_armaments' dbConn = dbMySQL_Connection(**c.creds) def dbConnRunQuery(): # Does not trap an exception; warning displayed to standard error. try: dbConn.runQuery(qry) except: print "dbConn.runQuery() caught an exception." def dbConnCursorExecute(): # Does not trap an exception; warning displayed to standard error. dbConn.getCursor() # try/except block does catches error without this try: dbConn.dbMySQL_Cursor.dbMySQL_Cursor.execute(qry) except Exception, e: print "dbConn.dbMySQL_Cursor.execute() caught an exception." print repr(e) def funcRunQueryNoCursor(): # Does not trap an exception; no warning displayed try: res = runQueryNoCursor(qry, dbConn) print 'Try worked. %s' % res except Exception, e: print "funcRunQueryNoCursor() caught an exception." print repr(e) #============================================================================= if __name__ == '__main__': print '\n' print 'EXAMPLE -- dbConnRunQuery()' dbConnRunQuery() print '\n' print 'EXAMPLE -- dbConnCursorExecute()' dbConnCursorExecute() print '\n' print 'EXAMPLE -- funcRunQueryNoCursor()' funcRunQueryNoCursor() print '\n'

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  • How do i cast an object to a string when object is not a string?

    - by acidzombie24
    I have class A, B, C. They all can implicitly convert to a string public static implicit operator A(string sz_) { ... return sz; } I have code that does this object AClassWhichImplicitlyConvertsToString { ... ((KnownType)(String)AClassWhichImplicitlyConvertsToString).KnownFunc() } The problem is, AClassWhichImplicitlyConvertsToString isnt a string even though it can be typecast into one implicitly. I get a bad cast exception. How do i say its ok as long as the class has an operator to convert into a string?

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  • Displaying pic for user through a question's answer

    - by bgadoci
    Ok, I am trying to display the profile pic of a user. The application I have set up allows users to create questions and answers (I am calling answers 'sites' in the code) the view in which I am trying to do so is in the /views/questions/show.html.erb file. It might also be of note that I am using the Paperclip gem. Here is the set up: Associations Users class User < ActiveRecord::Base has_many :questions, :dependent => :destroy has_many :sites, :dependent => :destroy has_many :notes, :dependent => :destroy has_many :likes, :through => :sites , :dependent => :destroy has_many :pics, :dependent => :destroy has_many :likes, :dependent => :destroy end Questions class Question < ActiveRecord::Base has_many :sites, :dependent => :destroy has_many :notes, :dependent => :destroy has_many :likes, :dependent => :destroy belongs_to :user end Answers (sites) class Site < ActiveRecord::Base belongs_to :question belongs_to :user has_many :notes, :dependent => :destroy has_many :likes, :dependent => :destroy has_attached_file :photo, :styles => { :small => "250x250>" } end Pics class Pic < ActiveRecord::Base has_attached_file :profile_pic, :styles => { :small => "100x100" } belongs_to :user end The /views/questions/show.html.erb is rendering the partial /views/sites/_site.html.erb which is calling the Answer (site) with: <% div_for site do %> <%=h site.description %> <% end %> I have been trying to do things like: <%=image_tag site.user.pic.profile_pic.url(:small) %> <%=image_tag site.user.profile_pic.url(:small) %> etc. But that is obviously wrong. My error directs me to the Questions#show action so I am imagining that I need to define something in there but not sure what. Is is possible to call the pic given the current associations, placement of the call, and if so what Controller additions do I need to make, and what line of code will call the pic? UPDATE: Here is the QuestionsController#show code: def show @question = Question.find(params[:id]) @sites = @question.sites.all(:select => "sites.*, SUM(likes.like) as like_total", :joins => "LEFT JOIN likes AS likes ON likes.site_id = sites.id", :group => "sites.id", :order => "like_total DESC") respond_to do |format| format.html # show.html.erb format.xml { render :xml => @question } end end

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  • jQuery fadeIn is not working in Internet Explorer

    - by Nazaf
    I have the following HTML DIV which does not work using FadeIn in IE: $(".tip").fadeIn("slow"); /* Is not working in IE. */ $(".tip").show(); /* Works well in IE, that's weird. */ <div class="tip" style="width: 220px; display: none;"> <div class="tip-header"> <span><b>Title</b></span> <div class="right close"><a href="javascript:void(0);">close</a> <img alt="" src="/Images/close-normal.png"/></div> </div> <div class="tip-content">EBody comes here.</div> </div> .tip { display: block; z-index: 99999; position: fixed; background-color: #ffffff; -moz-box-shadow: 2px 2px 10px 2px rgba(0, 0, 0, 0.6); -webkit-box-shadow: 2px 2px 10px 2px rgba(0, 0, 0, 0.6); border:solid 1px #82C2FA; -moz-border-radius: 8px; -webkit-border-radius: 8px; } .tip-header { padding: 8px; min-height: 10px; -moz-border-radius-topleft: 8px; -moz-border-radius-topright: 8px; -webkit-border-radius-topright: 8px; -webkit-border-radius-topleft: 8px; background-color: #CFE6FD; border-bottom: 1px solid #82C2FA; } .tip-header span { font-size: 14px; color: #666666; } .tip-content { padding: 8px; text-align: left; font-size: 12px; } .close, .whats-this { cursor: pointer; } .close a { color: #085FBC; text-decoration: none; } .close img { vertical-align: bottom; }

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  • To Interface or Not?: Creating a polymorphic model relationship in Ruby on Rails dynamically..

    - by Globalkeith
    Please bear with me for a moment as I try to explain exactly what I would like to achieve. In my Ruby on Rails application I have a model called Page. It represents a web page. I would like to enable the user to arbitrarily attach components to the page. Some examples of "components" would be Picture, PictureCollection, Video, VideoCollection, Background, Audio, Form, Comments. Currently I have a direct relationship between Page and Picture like this: class Page < ActiveRecord::Base has_many :pictures, :as => :imageable, :dependent => :destroy end class Picture < ActiveRecord::Base belongs_to :imageable, :polymorphic => true end This relationship enables the user to associate an arbitrary number of Pictures to the page. Now if I want to provide multiple collections i would need an additional model: class PictureCollection < ActiveRecord::Base belongs_to :collectionable, :polymorphic => true has_many :pictures, :as => :imageable, :dependent => :destroy end And alter Page to reference the new model: class Page < ActiveRecord::Base has_many :picture_collections, :as => :collectionable, :dependent => :destroy end Now it would be possible for the user to add any number of image collections to the page. However this is still very static in term of the :picture_collections reference in the Page model. If I add another "component", for example :video_collections, I would need to declare another reference in page for that component type. So my question is this: Do I need to add a new reference for each component type, or is there some other way? In Actionscript/Java I would declare an interface Component and make all components implement that interface, then I could just have a single attribute :components which contains all of the dynamically associated model objects. This is Rails, and I'm sure there is a great way to achieve this, but its a tricky one to Google. Perhaps you good people have some wise suggestions. Thanks in advance for taking the time to read and answer this.

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  • Null-free "maps": Is a callback solution slower than tryGet()?

    - by David Moles
    In comments to "How to implement List, Set, and Map in null free design?", Steven Sudit and I got into a discussion about using a callback, with handlers for "found" and "not found" situations, vs. a tryGet() method, taking an out parameter and returning a boolean indicating whether the out parameter had been populated. Steven maintained that the callback approach was more complex and almost certain to be slower; I maintained that the complexity was no greater and the performance at worst the same. But code speaks louder than words, so I thought I'd implement both and see what I got. The original question was fairly theoretical with regard to language ("And for argument sake, let's say this language don't even have null") -- I've used Java here because that's what I've got handy. Java doesn't have out parameters, but it doesn't have first-class functions either, so style-wise, it should suck equally for both approaches. (Digression: As far as complexity goes: I like the callback design because it inherently forces the user of the API to handle both cases, whereas the tryGet() design requires callers to perform their own boilerplate conditional check, which they could forget or get wrong. But having now implemented both, I can see why the tryGet() design looks simpler, at least in the short term.) First, the callback example: class CallbackMap<K, V> { private final Map<K, V> backingMap; public CallbackMap(Map<K, V> backingMap) { this.backingMap = backingMap; } void lookup(K key, Callback<K, V> handler) { V val = backingMap.get(key); if (val == null) { handler.handleMissing(key); } else { handler.handleFound(key, val); } } } interface Callback<K, V> { void handleFound(K key, V value); void handleMissing(K key); } class CallbackExample { private final Map<String, String> map; private final List<String> found; private final List<String> missing; private Callback<String, String> handler; public CallbackExample(Map<String, String> map) { this.map = map; found = new ArrayList<String>(map.size()); missing = new ArrayList<String>(map.size()); handler = new Callback<String, String>() { public void handleFound(String key, String value) { found.add(key + ": " + value); } public void handleMissing(String key) { missing.add(key); } }; } void test() { CallbackMap<String, String> cbMap = new CallbackMap<String, String>(map); for (int i = 0, count = map.size(); i < count; i++) { String key = "key" + i; cbMap.lookup(key, handler); } System.out.println(found.size() + " found"); System.out.println(missing.size() + " missing"); } } Now, the tryGet() example -- as best I understand the pattern (and I might well be wrong): class TryGetMap<K, V> { private final Map<K, V> backingMap; public TryGetMap(Map<K, V> backingMap) { this.backingMap = backingMap; } boolean tryGet(K key, OutParameter<V> valueParam) { V val = backingMap.get(key); if (val == null) { return false; } valueParam.value = val; return true; } } class OutParameter<V> { V value; } class TryGetExample { private final Map<String, String> map; private final List<String> found; private final List<String> missing; public TryGetExample(Map<String, String> map) { this.map = map; found = new ArrayList<String>(map.size()); missing = new ArrayList<String>(map.size()); } void test() { TryGetMap<String, String> tgMap = new TryGetMap<String, String>(map); for (int i = 0, count = map.size(); i < count; i++) { String key = "key" + i; OutParameter<String> out = new OutParameter<String>(); if (tgMap.tryGet(key, out)) { found.add(key + ": " + out.value); } else { missing.add(key); } } System.out.println(found.size() + " found"); System.out.println(missing.size() + " missing"); } } And finally, the performance test code: public static void main(String[] args) { int size = 200000; Map<String, String> map = new HashMap<String, String>(); for (int i = 0; i < size; i++) { String val = (i % 5 == 0) ? null : "value" + i; map.put("key" + i, val); } long totalCallback = 0; long totalTryGet = 0; int iterations = 20; for (int i = 0; i < iterations; i++) { { TryGetExample tryGet = new TryGetExample(map); long tryGetStart = System.currentTimeMillis(); tryGet.test(); totalTryGet += (System.currentTimeMillis() - tryGetStart); } System.gc(); { CallbackExample callback = new CallbackExample(map); long callbackStart = System.currentTimeMillis(); callback.test(); totalCallback += (System.currentTimeMillis() - callbackStart); } System.gc(); } System.out.println("Avg. callback: " + (totalCallback / iterations)); System.out.println("Avg. tryGet(): " + (totalTryGet / iterations)); } On my first attempt, I got 50% worse performance for callback than for tryGet(), which really surprised me. But, on a hunch, I added some garbage collection, and the performance penalty vanished. This fits with my instinct, which is that we're basically talking about taking the same number of method calls, conditional checks, etc. and rearranging them. But then, I wrote the code, so I might well have written a suboptimal or subconsicously penalized tryGet() implementation. Thoughts?

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