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  • should variable be released or not? iphone-sdk

    - by psebos
    Hi, In the following piece of code (from a book) data is an NSDictionary *data; defined in the header (no property). In the viewDidLoad of the controller the following occurs: - (void)viewDidLoad { [super viewDidLoad]; NSArray *keys = [NSArray arrayWithObjects:@"home", @"work", nil]; NSArray *homeDVDs = [NSArray arrayWithObjects:@"Thomas the Builder", nil]; NSArray *workDVDs = [NSArray arrayWithObjects:@"Intro to Blender", nil]; NSArray *values = [NSArray arrayWithObjects:homeDVDs, workDVDs, nil]; data = [[NSDictionary alloc] initWithObjects:values forKeys:keys]; } Since I am really new to objective-c can someone explain to me why I do not have to retain the variables keys,homeDVDs,workDVDs and values prior exiting the function? I would expect prior the data allocation something like: [keys retain]; [homeDVDs retain]; [workDVDs retain]; [values retain]; or not? Does InitWithObjects copies (recursively) all objects into a new table? Assuming we did not have the last line (data allocation) should we release all the NSArrays prior exiting the function (or we could safely assumed that all NSArrays will be autoreleased since there is no alloc for each one?) Thanks!!!!

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  • Flipping View transition becomes clunky when using UIPickerViews with a large number of elements

    - by user302246
    I have a very simple app created with the Utility Application project template on XCode. My MainView has two UIPickerView components and two buttons. The FlipSideView has another UIPickerView. The pickers on the main view each have 4 segments and each segment has 8 rows. The picker on the flip side has just 1 segment with 8 rows. All rows on all pickers are just text. With just this setup, pressing the button to flip the view back and forth displays a noticeable delay before the animation actually starts, and then the animation actually seems to go faster than what it should, like it's trying to make up for the lost time. I removed the pickers in interface builder and loaded the app on the phone and the animation now seems natural. I also tried just one picker (the flipside one) and things still seem normal. So my current theory is that the number of objects involved in the main view is the cause. The thing is that I don't think it's that many (4 x 8 x 2 = 64), but I could be completely wrong. This is pretty much my first app so maybe I'm just doing something grossly wrong, or maybe the phone is has a lot more limited processing than I thought. I am thinking of creating the picker views with pickerView:viewForRow:forComponent:reusingView: to see if this hopefully performs better, but I'm not sure if this is just a waste of time. Any suggestions? Thanks Ruy P.S.: Testing on a 3G phone on 3.1.2

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  • How to build a JSON response by combining @foo.to_json(options) and @bars.to_json(options) in Rails

    - by smotchkkiss
    First, the desired result I have User and Item models. I'd like to build a JSON response that looks like this: { "user": {"username":"Bob!","foo":"whatever","bar":"hello!"}, "items": [ {"id":1, "name":"one", "zim":"planet", "gir":"earth"}, {"id":2, "name":"two", "zim":"planet", "gir":"mars"} ] } However, my User and Item model have more attributes than just those. I found a way to get this to work, but beware, it's not pretty... Please help... My hacks home_controller.rb class HomeController < ApplicationController def observe respond_to do |format| format.js { render :json => Observation.new(current_user, @items).to_json } end end end observation.rb # NOTE: this is not a subclass of ActiveRecord::Base # this class just serves as a container to aggregate all "observable" objects class Observation attr_accessor :user, :items def initialize(user, items) self.user = user self.items = items end # The JSON needs to be decoded before it's sent to the `to_json` method in the home_controller otherwise the JSON will be escaped... # What a mess! def to_json { :user => ActiveSupport::JSON.decode(user.to_json(:only => :username, :methods => [:foo, :bar])), :items => ActiveSupport::JSON.decode(auctions.to_json(:only => [:id, :name], :methods => [:zim, :gir])) } end end

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  • reddit style voting with django

    - by dotty
    Hay i need to hand implemeneting a voting system into a model. I've had a huge helping hand from Mike DeSimone making this work in the first place, but i need to expand upon his work. Here is my current code View def show_game(request): game = Game.objects.get(pk=1) discussions = game.gamediscussion_set.filter(reply_to=None) d = { 'game':game, 'discussions':discussions } return render_to_response('show_game', d) Template <ul> {% for discussion in discussions %} {{ discussion.html }} {% endfor %} </ul> Model class GameDiscussion(models.Model): game = models.ForeignKey(Game) message = models.TextField() reply_to = models.ForeignKey('self', related_name='replies', null=True, blank=True) created_on = models.DateTimeField(blank=True, auto_now_add=True) userUpVotes = models.ManyToManyField(User, blank=True, related_name='threadUpVotes') userDownVotes = models.ManyToManyField(User, blank=True, related_name='threadDownVotes') def html(self): DiscussionTemplate = loader.get_template("inclusions/discussionTemplate") return DiscussionTemplate.render(Context({ 'discussion': self, 'replies': [reply.html() for reply in self.replies.all()] })) DiscussionTemplate <li> {{ discussion.message }} {% if replies %} <ul> {% for reply in replies %} {{ reply }} {% endfor %} </ul> {% endif %} </li> As you can see we have 2 fields userUpVotes and userDownVotes on the model, these will calculate how to order the discussions and replies. How would i implement these 2 fields to order the replies and discussions based on votes? Any help would be great!

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  • Query Level 2 Caching throwing ClassCastException

    - by Sameer Malhotra
    Hi, I am using JPA and Hibernate for the database. I have configured (EHCacache) second level cache and query level cache, but just to make sure that caching is working I was trying to get the statistics which is throwing class cast exception.Any help will be highly appreciated. My main goal is to see all the objects which have been cached to make sure that the caching is working properly. Here is the code: public List<CodeValue> findByCodetype(String propertyName) { try { final String queryString = "select model from CodeValue model where model.codetype" + "= :propertyValue" + " order by model.code"; Query query = em.createQuery(queryString); query.setHint("org.hibernate.cacheable", true); query.setHint("org.hibernate.cacheRegion", "query.findByCodetype"); query.setParameter("propertyValue", propertyName); List resultList = query.getResultList(); org.hibernate.Session session = (Session) em.getDelegate(); SessionFactory sessionFactory = session.getSessionFactory(); Map cacheEntries = sessionFactory.getStatistics() .getSecondLevelCacheStatistics("query.findByCodetype") .getEntries(); logger.info("The statistics are: " + cacheEntries); return resultList; } catch (RuntimeException re) { logger.error("findByCodetype failed in trauma patient", re); throw re; } } The error is existing right when I am trying to print the statistics. Below is exception: [6/7/10 19:23:17:059 GMT] 00000034 SystemOut O java.lang.ClassCastException: org.hibernate.cache.QueryKey incompatible with org.hibernate.cache.CacheKey at org.hibernate.stat.SecondLevelCacheStatistics.getEntries(SecondLevelCacheStatistics.java:51) at com.idph.trauma.registry.service.TraumaPatientDAO.findByCodetype(TraumaPatientDAO.java:439) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:615) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy209.findByCodetype(Unknown Source) Do you know what's going on?

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  • How to use javascript class from within document ready

    - by Richard
    Hi, I have this countdown script wrapped as an object located in a separate file Then when I want to setup a counter, the timeout function in the countdown class can not find the object again that I have setup within the document ready. I sort of get that everything that is setup in the document ready is convined to that scope, however it is possible to call functions within other document ready´s. Does anyone has a solution on how I could setup multiple counters slash objects. Or do those basic javascript classes have to become plugins This is some sample code on how the class begins function countdown(obj) { this.obj = obj; this.Div = "clock"; this.BackColor = "white"; this.ForeColor = "black"; this.TargetDate = "12/31/2020 5:00 AM"; this.DisplayFormat = "%%D%% Days, %%H%% Hours, %%M%% Minutes, %%S%% Seconds."; this.CountActive = true; this.DisplayStr; this.Calcage = cd_Calcage; this.CountBack = cd_CountBack; this.Setup = cd_Setup; } thanks, Richard

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  • PulpCore OGG music playback - can't loop as soon as I animate the musicVolume property

    - by Peter Perhác
    I have been experimenting with PulpCore for about a week or so and I am enjoying it very much but today I ran into a problem that I can't quite figure out. Sound bgMusic = Sound.load("music/music.ogg"); Playback musicPlayback; ... musicVolume = new Fixed(0.75); musicPlayback = bgMusic.loop(musicVolume); //TODO figure out why it's NOT looping when volume is animated // musicVolume.animate(0, musicVolume.get(), FADE_IN_TIME); This code, for as long as the last line is commented out, plays the music.ogg again and again in an endless loop (which I can stop by calling stop on the Playback object returned from loop(). However, I would like the music to fade in smoothly, so following the advice of the PulpCore API docs, I added the last line which will create the fade-in but the music will only play once and then stop. I wonder why is that? Here is a bit of the documentation: Playback pulpcore.sound.Sound.loop(Fixed level) Loops this sound clip with the specified volume level (0.0 to 1.0). The level may have a property animation attached. Parameters: level Returns: a Playback object for this unique sound playback (one Sound can have many simultaneous Playback objects) or null if the sound could not be played. So what could be the problem? I repeat, with the last line, the sound fades in but doesn't loop, without it it loops but starts with the specified 0.75 volume level.

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  • javascript pausing consistently. How do I find what is causing it to pause?

    - by pedalpete
    I've got a fairly ajax heavy site and I'm trying to tune the performance. I have a function that runs between 20 & 200 times, depending on the user. I'm outputting the time the function takes to execute via console.time in firefox. The function takes about 4-6ms to complete. The strange thing is that on my larger test with 200 or runs through that function, it runs through the first 31, then seems to pause for almost a second before completing the last 170 or so. However, that 'pause' doesn't show up in the console.time logs, and I'm not running any other functions, and the object that gets passed to the function looks the same as all other objects that get passed in. The function is called like this for (var s in thisGroup.events){ showEvent(thisGroup.events[s]) } so, I don't see how or why it would suddenly pause near the beginning. but only pause once and then continue through. The pause ALWAYS happens on the 31st time through the function. I've taken a close look at the 'thisGroup.events[s]' that it is being run through, and it looks like this for #31 "eventId":"5106", "sid":"68", "gid":"29", "uid":"70","type":"event", "startDate":"2010-03-22","startTime":"6:00 PM","endDate":"2010-03-22","endTime":"11:00 PM","durationLength":"5", "durationTime":"5:00", "note":"", "desc":"event" The event immediately after the pause, #32 looks like this "eventId":"5111", "sid":"68", "gid":"29", "uid":"71","type":"event", "startDate":"2010-03-22","startTime":"6:00 PM","endDate":"2010-03-22","endTime":"11:00 PM","durationLength":"5", "durationTime":"5:00", "note":"", "desc":"event" another event that runs through no problem looks like this "eventId":"5113", "sid":"68", "gid":"29", "uid":"72","type":"event", "startDate":"2010-03-22","startTime":"4:30 PM","endDate":"2010-03-22","endTime":"11:00 PM","durationLength":"6.5", "durationTime":"6:30", "note":"", "desc":"event" From the console outputs, it doesn't appear as there is anything hanging or taking up time in the function itself, as the console.time for each event including #31,32 is 4ms. Another strange thing here is that the total time running the for loop across the entire object is coming out as 1014ms which is right for 200 events at 4-6ms each. Any suggestions on how to find this 'pause'? I find it very interesting that it is consistently happening between #31 & #32 only!

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  • How to store a list in a column of a database table.

    - by John Berryman
    Howdy! So, per Mehrdad's answer to a related question, I get it that a "proper" database table column doesn't store a list. Rather, you should create another table that effectively holds the elements of said list and then link to it directly or through a junction table. However, the type of list I want to create will be composed of unique items (unlike the linked question's fruit example). Furthermore, the items in my list are explicitly sorted - which means that if I stored the elements in another table, I'd have to sort them every time I accessed them. Finally, the list is basically atomic in that any time I wish to access the list, I will want to access the entire list rather than just a piece of it - so it seems silly to have to issue a database query to gather together pieces of the list. AKX's solution (linked above) is to serialize the list and store it in a binary column. But this also seems inconvenient because it means that I have to worry about serialization and deserialization. Is there any better solution? If there is no better solution, then why? It seems that this problem should come up from time to time. ... just a little more info to let you know where I'm coming from. As soon as I had just begun understanding SQL and databases in general, I was turned on to LINQ to SQL, and so now I'm a little spoiled because I expect to deal with my programming object model without having to think about how the objects are queried or stored in the database. Thanks All! John

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  • Getting "[Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near 'Microsoft.'

    - by brohjoe
    Hi Experts, I'm getting an error, "[Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near 'Microsoft.' Here is the code: Dim conn As ADODB.Connection Dim rst As ADODB.Recordset Dim stSQL As String Public Sub loadData() 'This was set up using Microsoft ActiveX Data Components version 6.0. 'Create ADODB connection object, open connection and construct the connection string object which is the DSN name. Set conn = New ADODB.Connection conn.ConnectionString = "sql_server" conn.Open 'conn.Execute (strSQL) On Error GoTo ErrorHandler 'Open Excel and run query to export data to SQL Server. strSQL = "SELECT * INTO SalesOrders FROM OPENDATASOURCE(Microsoft.ACE.OLEDB.12.0;" & _ "Data Source=C:\Workbook.xlsx;" & _ "Extended Properties=Excel 12.0; [Sales Orders])" conn.Execute (strSQL) 'Error handling. ErrorExit: 'Reclaim memory from the cntection objects Set rst = Nothing Set conn = Nothing Exit Sub ErrorHandler: MsgBox Err.Description, vbCritical Resume ErrorExit 'clean up and reclaim memory resources. conn.Close If CBool(cnt.State And adStateOpen) Then Set rst = Nothing Set conn = Nothing End If End Sub

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  • Fast, very lightweight algorithm for camera motion detection?

    - by Ertebolle
    I'm working on an augmented reality app for iPhone that involves a very processor-intensive object recognition algorithm (pushing the CPU at 100% it can get through maybe 5 frames per second), and in an effort to both save battery power and make the whole thing less "jittery" I'm trying to come up with a way to only run that object recognizer when the user is actually moving the camera around. My first thought was to simply use the iPhone's accelerometers / gyroscope, but in testing I found that very often people would move the iPhone at a consistent enough attitude and velocity that there wouldn't be any way to tell that it was still in motion. So that left the option of analyzing the actual video feed and detecting movement in that. I got OpenCV working and tried running their pyramidal Lucas-Kanade optical flow algorithm, which works well but seems to be almost as processor-intensive as my object recognizer - I can get it to an acceptable framerate if I lower the depth levels / downsample the image / track fewer points, but then accuracy suffers and it starts to miss some large movements and trigger on small hand-shaking-y ones. So my question is, is there another optical flow algorithm that's faster than Lucas-Kanade if I just want to detect the overall magnitude of camera movement? I don't need to track individual objects, I don't even need to know which direction the camera is moving, all I really need is a way to feed something two frames of video and have it tell me how far apart they are.

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  • Translating Where() to sql

    - by MBoros
    Hi. I saw DamienG's article (http://damieng.com/blog/2009/06/24/client-side-properties-and-any-remote-linq-provider) in how to map client properties to sql. i ran throgh this article, and i saw great potential in it. Definitely mapping client properties to SQL is an awesome idea. But i wanted to use this for something a bit more complicated then just concatenating strings. Atm we are trying to introduce multilinguality to our Business objects, and i hoped we could leave all the existing linq2sql queries intact, and just change the code of the multilingual properties, so they would actually return the given property in the CurrentUICulture. The first idea was to change these fields to XMLs, and then try the Object.Property.Elements().Where(...), but it got stuck on the Elements(), as it couldnt translate it to sql. I read somewhere that XML fields are actually regarded as strings, and only on the app server they become XElements, so this way the filtering would be on the app server anyways, not the DB. Fair point, it wont work like this. Lets try something else... SO the second idea was to create a PolyGlots table (name taken from http://weblogic.sys-con.com/node/102698?page=0,1), a PolyGlotTranslations table and a Culture table, where the PolyGlots would be referenced from each internationalized property. This way i wanted to say for example: private static readonly CompiledExpression<Announcement, string> nameExpression = DefaultTranslationOf<Announcement> .Property(e => e.Name) .Is(e=> e.NamePolyGlot.PolyGlotTranslations .Where(t=> t.Culture.Code == Thread.CurrentThread.CurrentUICulture.Name) .Single().Value ); now unfortunately here i get an error that the Where() function cannot be translated to sql, what is a bit disappointing, as i was sure it will go through. I guess it is failing, cause the IEntitySet is basically an IEnumerable, not IQueryable, am i right? Is there another way to use the compiledExpressions class to achieve this goal? Any help appreciated.

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  • what kind of relationship is there between a common wall and the rooms that located next to it?

    - by siamak
    I want to know whats the Relationship between a common wall (that are located In an adjoining room ) and the rooms. As i know the relationship between a room and its walls is Composition not Aggregation (am i right ?) And according to the definition of Composition the contained object can't be shared between two containers, whereas in aggregation it is possible. now i am confused that whats the best modeling approach to represent the relationship between a common wall and the rooms located next to it ? It would be highly Appreciated if you could provide your advices with some code. |--------|--------| Approch1: (wall class ---- room class) /Composition Approach2: wall class ----- room class /Aggregation Approch3: we have a wall class and a Common wall class , Common wall class inherits from wall class adjoining room class ---- (1) Common wall class /Aggregation adjoining room class ---- (6) wall class / composition Approach4: I am a developer not a designer :) so this is my idea : class Room { private wall _firstwall ; private wall _secondtwall; private wall _thirdwall ; private wall _commonwall ; public Room( CommonWall commonwall) { _firstwall=new Wall(); _secondtwall=new Wall(); _thirdwall=new Wall(); _commonwall=commonwall; } } Class CommonWall:Wall { //... } // in somewher : static void main() { Wall _commonWall=new Wall(); Room room1=new Room(_commonWall); Room room2=new Room(_commonWall); Room [] adjacentRoom =new Room[2]{room1,room2}; } Edit 1: I think this is a clear question but just for more clarification : The point of the question is to find out whats the best pattern or approach to model a relationship for an object that is a component of two other objects in the same time. and about my example : waht i mean by a "room" ?,surely i mean an enclosed square room with 4 walls and one door.but in this case one of these walls is a common wall and is shared between two adjacent rooms.

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  • How should I avoid memoization causing bugs in Ruby?

    - by Andrew Grimm
    Is there a consensus on how to avoid memoization causing bugs due to mutable state? In this example, a cached result had its state mutated, and therefore gave the wrong result the second time it was called. class Greeter def initialize @greeting_cache = {} end def expensive_greeting_calculation(formality) case formality when :casual then "Hi" when :formal then "Hello" end end def greeting(formality) unless @greeting_cache.has_key?(formality) @greeting_cache[formality] = expensive_greeting_calculation(formality) end @greeting_cache[formality] end end def memoization_mutator greeter = Greeter.new first_person = "Bob" # Mildly contrived in this case, # but you could encounter this in more complex scenarios puts(greeter.greeting(:casual) << " " << first_person) # => Hi Bob second_person = "Sue" puts(greeter.greeting(:casual) << " " << second_person) # => Hi Bob Sue end memoization_mutator Approaches I can see to avoid this are: greeting could return a dup or clone of @greeting_cache[formality] greeting could freeze the result of @greeting_cache[formality]. That'd cause an exception to be raised when memoization_mutator appends strings to it. Check all code that uses the result of greeting to ensure none of it does any mutating of the string. Is there a consensus on the best approach? Is the only disadvantage of doing (1) or (2) decreased performance? (I also suspect freezing an object may not work fully if it has references to other objects) Side note: this problem doesn't affect the main application of memoization: as Fixnums are immutable, calculating Fibonacci sequences doesn't have problems with mutable state. :)

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  • Javascript: Adding selected text to an array

    - by joeybaker
    My goal: each time a user selects text, and clicks a button, that text gets added to an array. The problem: each time the button is pressed, the all objects of the array get overridden with the currently selected text. I'd really appreciate help changing the behavior so that the selected text doesn't override all previous array items. <script type="text/javascript"> var selects = new Array(); selects.push("1"); function getSelText() { var i = 0; while (i<1) { var txt = [null]; var x = 0; if (window.getSelection) { txt[x] = window.getSelection(); } else if (document.getSelection) { txt[x] = document.getSelection(); } else if (document.selection) { txt[x] = document.selection.createRange().text; } else return; selects.push(txt); x++; i++; }; document.menu.selectedtext.value = selects; } </script> <form class="menu" name="menu"> <input type="button" value="highlight" class="highlightButton" onmousedown="getSelText()"/> <textarea name="selectedtext" rows="5" cols="20"></textarea> </form> <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>

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  • Best way to databind a Winforms control to a nullable type?

    - by Steve Hiner
    I'm currently using winforms databinding to wire up a data editing form. I'm using the netTiers framework through CodeSmith to generate my data objects. For database fields that allow nulls it creates nullable types. I've found that using winforms databinding the controls won't bind properly to nullable types. I've seen solutions online suggesting that people create new textbox classes that can handle the nullable types but that could be a pain having to swap out the textboxes on the forms I've already created. Initially I thought it would be great to use an extension method to do it. Basically creating an extension property for the textbox class and bind to that. From my limited extension method experience and doing a bit of checking online it looks like you can't do an extension property. As far as I can tell, binding has to be through a property since it needs to be able to get or set the value so an extension method wouldn't work. I'd love to find a clean way to retrofit these forms using something like extension methods but if I have to create new textbox and combo box controls that's what I'll do. My project is currently limited to .Net 2.0 due to the requirement to run on Windows 2000. Any suggestions?

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  • Polymorphic Queue

    - by metdos
    Hello Everyone, I'm trying to implement a Polymorphic Queue. Here is my trial: QQueue <Request *> requests; while(...) { QString line = QString::fromUtf8(client->readLine()).trimmed(); if(...)){ Request *request=new Request(); request->tcpMessage=line.toUtf8(); request->decodeFromTcpMessage(); //this initialize variables in request using tcpMessage if(request->requestType==REQUEST_LOGIN){ LoginRequest loginRequest; request=&loginRequest; request->tcpMessage=line.toUtf8(); request->decodeFromTcpMessage(); requests.enqueue(request); } //Here pointers in "requests" do not point to objects I created above, and I noticed that their destructors are also called. LoginRequest *loginRequest2=dynamic_cast<LoginRequest *>(requests.dequeue()); loginRequest2->decodeFromTcpMessage(); } } Unfortunately, I could not manage to make work Polymorphic Queue with this code because of the reason I mentioned in second comment.I guess, I need to use smart-pointers, but how? I'm open to any improvement of my code or a new implementation of polymorphic queue. Thanks.

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  • Why is creating a ring buffer shared by different processes so hard (in C++), what I am doing wrong?

    - by recipriversexclusion
    I am being especially dense about this but it seems I'm missing an important, basic point or something, since what I want to do should be common: I need to create a fixed-size ring buffer object from a manager process (Process M). This object has write() and read() methods to write/read from the buffer. The read/write methods will be called by independent processes (Process R and W) I have implemented the buffer, SharedBuffer<T&>, it allocates buffer slots in SHM using boost::interprocess and works perfectly within a single process. I have read the answers to this question and that one on SO, as well as asked my own, but I'm still in the dark about how to have different processes access methods from a common object. The Boost doc has an example of creating a vector in SHM, which is very similar to what I want, but I want to instantiate my own class. My current options are: Use placement new, as suggested by Charles B. to my question; however, he cautions that it's not a good idea to put non-POD objects in SHM. But my class needs the read/write methods, how can I handle those? Add an allocator to my class definition, e.g. have SharedBuffer<T&, Alloc> and proceed similarly to the vector example given in boost. This sounds really complicated. Change SharedBuffer to a POD class, i.e. get rid of all the methods. But then how to synchronize reading and writing between processes? What am I missing? Fixed-length ring buffers are very common, so either this problem has a solution or else I'm doing something wrong.

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  • Multiple threads modifying a collection in Java??

    - by posdef
    Hi, The project I am working on requires a whole bunch of queries towards a database. In principle there are two types of queries I am using: read from excel file, check for a couple of parameters and do a query for hits in the database. These hits are then registered as a series of custom classes. Any hit may (and most likely will) occur more than once so this part of the code checks and updates the occurrence in a custom list implementation that extends ArrayList. for each hit found, do a detail query and parse the output, so that the classes created in (I) get detailed info. I figured I would use multiple threads to optimize time-wise. However I can't really come up with a good way to solve the problem that occurs with the collection these items are stored in. To elaborate a little bit; throughout the execution objects are supposed to be modified by both (I) and (II). I deliberately didn't c/p any code, as it would be big chunks of code to make any sense.. I hope it make some sense with the description above. Thanks,

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  • findViewById returns null in new Intent

    - by drozzy
    I am having a problem where in the started Intent, the findViewById returns null. Is there anything special I should know about starting a new intent? It goes something like this for me: //in the MainList class Intent stuffList = new Intent(this, StuffList.class); then in the new Stuff's constructor: public class StuffList extends ListActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.setContentView(R.layout.stuff_list); ... this.setListAdapter(new StuffAdapter(this, my_cursor)); and in the StuffAdapter I do my usual view and data retrieval. Note the line where findViewById returns null: class ViewWrapper{ View base; TextView label = null; ViewWrapper(View base){ this.base = base; } TextView getLabel(){ if(label == null){ label = (TextView)base.findViewById(R.id.my_label); // returns NULL } return label;} } class StuffAdapter extends CursorAdapter{ StuffAdapter(Context context, Cursor cursor){ super(context, cursor); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { LayoutInflater inflater = getLayoutInflater(); View row = inflater.inflate(R.layout.stuff_list, parent, false); ViewWrapper wrapper = new ViewWrapper(row); row.setTag(wrapper); return(row); } @Override public void bindView(View row, Context context, Cursor cursor) { ViewWrapper wrapper = (ViewWrapper)row.getTag(); TextView label = wrapper.getLabel(); // also NULL //this throws exception of course label.setText(cursor.getString("title")); } } The curious thing is that in the class that calls intent (MainList class), I do Exactly the same thing (i list a bunch of objects), and it Works! however when I try to do it in an Intent - it can't seem to find the view by id.

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  • Simple NSTableView bindings example

    - by sirjorj
    I am trying to populate a 2-column NSVTableView via bindings, but the data is not showing up in the table. In XCode: I have a NSMutableArray in my AppDelegate that will hold the data, as well as the corresponding @property and @synthesize. On an event, I call [removeAllObjects] on the NSMutableArray and repopulate it with some NSDictionary objects. Each dictionary contains 2 KVP's: a NAME and a VALUE. In IB: I added an NSArrayController and bound it's Content Array to my AppDelegate and set the ModelKeyPath to the name of the NSMutableArray in the AppDelegate. On the NSTableView, I bound the Content to the ArrayController. ControllerKey = "arrangedObjects", ModelKeyPath = empty. For each of the two columns, I bound the Value to the AppController and set the ModelKeyPaths to NAME and VALUE respectively. ControllerKey = "ArrangedObjects". I have tried several other things, such as using an NSArray in the app delegate and making a new one every time I need to update the values. There must be some tiny little thing I am forgetting. What is it? jorj

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  • MVVM pattern: ViewModel updates after Model server roundtrip

    - by Pavel Savara
    I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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  • What does flushing thread local memory to global memory mean?

    - by Jack Griffith
    Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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  • [Cocoa] Binding CoreData Managed Object to NSTextFieldCell subclass

    - by ndg
    I have an NSTableView which has its first column set to contain a custom NSTextFieldCell. My custom NSTextFieldCell needs to allow the user to edit a "desc" property within my Managed Object but to also display an "info" string that it contains (which is not editable). To achieve this, I followed this tutorial. In a nutshell, the tutorial suggests editing your Managed Objects generated subclass to create and pass a dictionary of its contents to your NSTableColumn via bindings. This works well for read-only NSCell implementations, but I'm looking to subclass NSTextFieldCell to allow the user to edit the "desc" property of my Managed Object. To do this, I followed one of the articles comments, which suggests subclassing NSFormatter to explicitly state which Managed Object property you would like the NSTextFieldCell to edit. Here's the suggested implementation: @implementation TRTableDescFormatter - (BOOL)getObjectValue:(id *)anObject forString:(NSString *)string errorDescription:(NSString **)error { if (anObject != nil){ *anObject = [NSDictionary dictionaryWithObject:string forKey:@"desc"]; return YES; } return NO; } - (NSString *)stringForObjectValue:(id)anObject { if (![anObject isKindOfClass:[NSDictionary class]]) return nil; return [anObject valueForKey:@"desc"]; } - (NSAttributedString*)attributedStringForObjectValue:(id)anObject withDefaultAttributes:(NSDictionary *)attrs { if (![anObject isKindOfClass:[NSDictionary class]]) return nil; NSAttributedString *anAttributedString = [[NSAttributedString alloc] initWithString: [anObject valueForKey:@"desc"]]; return anAttributedString; } @end I assign the NSFormatter subclass to my cell in my NSTextFieldCell subclass, like so: - (void)awakeFromNib { TRTableDescFormatter *formatter = [[[TRTableDescFormatter alloc] init] autorelease]; [self setFormatter:formatter]; } This seems to work, but is extremely patch. On occasion, clicking to edit a row will cause its value to nullify. On other occasions, the value you enter on one row will populate other rows within the table. I've been doing a lot of reading on this subject and would really like to get to the bottom of this. What's more frustrating is that my NSTextFieldCell is rendering exactly how I would like it to. This editing issue is my last obstacle! If anyone can help, that would be greatly appreciated.

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  • ASP Menu driving me insane

    - by simplesimon
    Hi there, I am trying to create a menu using ASP (I have never used ASP before, im a PHP man) using values stored in a database. basically the html layout i want is as such: <ul> <li> <ul class="sub-menu"> <li class="sub-menu-li">Test</li> </ul> </li> </ul> I need to loop around the root menu items rs("AD_Level") which is equal to 0 for root objects, then inside that loop, lop around anything that has the same parent id eg if the current record is AD_Level =0 and AD_Parent=5 then loop around all items with AD_Parent 5 and AD_Level != 0 and insert the values into html and so on and so forth. Please help! I am struggling with a new language and cannot see a way to do this without losing sanity Edit (Extracted from Comment by OP) while not rsAdmin.eof sPar = rsAdmin("ad_parent" if rsAdmin("AD_Level")=0 then while not rsAdmin2.eof if rsAdmin2("AD_Level")<>0 and rsAdmin2("ad_parent")=sPar and rsAdmin2("AD_Sec_Level")=>2 then response.write rsAdmin("AD_Menu") end if rsAdmin2.movenext wend end if '' # if not rsAdmin.eof then sPar=rsAdmin("AD_parent") rsAdmin.movenext wend that is my code

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