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• How is a constructor executed?

  - by simion

  I am doing some reviison from the lecture slides and it says a constructor is executed in the following way; If the constructor starts with this, recursively execute the indicated constructor, then go to step 4. Invoke the explicitly or implicitly indicated superclass constructor (unless this class is java.lang.Object) Initialise the fields of the object in the order in which they were declared in this class Execute the rest of the body of this constructor. What i dont undertsand is that, a constructor can never "start" with this, because even if it forms no class heirarchy/relationship then super() is inserted by default. How would this fit in with the description above? Thanks

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• jQuery/JSON/PHP failing

  - by user730936

  I am trying to call a php script that accepts JSON data, writes it into a file and returns simple text response using jQuery/AJAX call. jQuery code : $("input.callphp").click(function() { var url_file = myurl"; $.ajax({type : "POST", url : url_file, data : {'puzzle': 'Reset!'}, success : function(data){ alert("Success: " + data); }, error : function (data) { alert("Error: " + data); }, dataType : 'text' }); }); PHP Code : <?php $thefile = "new.json"; /* Our filename as defined earlier */ $towrite = $_POST["puzzle"]; /* What we'll write to the file */ $openedfile = fopen($thefile, "w"); fwrite($openedfile, $towrite); fclose($openedfile); echo "<br> <br>".$towrite; ?> However, the call is never a success and always gives an error with an alert "Error : [Object object]".

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• Returning objects with dynamic memory

  - by Caulibrot

  I'm having trouble figuring out a way to return an object (declared locally within the function) which has dynamic memory attached to it. The problem is the destructor, which runs and deletes the dynamic memory when the object goes out of scope, i.e. when I return it and want to use the data in the memory that has been deleted! I'm doing this for an overloaded addition operator. I'm trying to do something like: MyObj operator+( const MyObj& x, const MyObj& y ) { MyObj z; // code to add x and y and store in dynamic memory of z return z; } My destructor is simply: MyObj::~MyObj() { delete [] ptr; } Any suggestions would be much appreciated!

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• Filtering SQLAlchemy query on attribute_mapped_collection field of relationship

  - by bsa

  I have two classes, Tag and Hardware, defined with a simple parent-child relationship (see the full definition at the end). Now I want to filter a query on Tag using the version field in Hardware through an attribute_mapped_collection, eg: def get_tags(order_code=None, hardware_filters=None): session = Session() query = session.query(Tag) if order_code: query = query.filter(Tag.order_code == order_code) if hardware_filters: for k, v in hardware_filters.iteritems(): query = query.filter(getattr(Tag.hardware, k).version == v) return query.all() But I get: AttributeError: Neither 'InstrumentedAttribute' object nor 'Comparator' object associated with Tag.hardware has an attribute 'baseband The same thing happens if I strip it back by hard-coding the attribute, eg: query.filter(Tag.hardware.baseband.version == v) I can do it this way: query = query.filter(Tag.hardware.any(artefact=k, version=v)) But why can't I filter directly through the attribute? Class definitions class Tag(Base): __tablename__ = 'tag' tag_id = Column(Integer, primary_key=True) order_code = Column(String, nullable=False) version = Column(String, nullable=False) status = Column(String, nullable=False) comments = Column(String) hardware = relationship( "Hardware", backref="tag", collection_class=attribute_mapped_collection('artefact'), ) __table_args__ = ( UniqueConstraint('order_code', 'version'), ) class Hardware(Base): __tablename__ = 'hardware' hardware_id = Column(Integer, primary_key=True) tag_id = Column(String, ForeignKey('tag.tag_id')) product_id = Column(String, nullable=True) artefact = Column(String, nullable=False) version = Column(String, nullable=False)

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• c++ classes & lua

  - by anon

  I want to have C++ objects that I can read/write in both C++ & Lua. I have looked at: http://www.lua.org/pil/28.html However, I do not like that solution, since my objects have constructors & destructors (and they are important as I use RAII and these take care of reference counts). What I don't like in the PIL solution is that the object is allocated in Lua's heap. What i want instead, is to create hte C++ object on my own, and just have lua have a way to do get/set on them. Does anyone have a good tutorial/link on this? Tanks!

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• How do I tell if the ObjectDataSource OnSelected event was called for the selectmethod or selectcou

  - by itchi

  I have an object datasource that looks like this: <asp:ObjectDataSource ID="obdsList" runat="server" EnablePaging="True" SelectCountMethod="GetCountByID" SortParameterName="sortExpression" OldValuesParameterFormatString="original_{0}" SelectMethod="GetByID" TypeName="Services.Users" onselected="obdsList_Selected"> <SelectParameters> <asp:QueryStringParameter Name="ID" QueryStringField="ID" Type="Int32" /> </SelectParameters> </asp:ObjectDataSource> And a onselected event like this: protected void obdsList_Selected(object sender, ObjectDataSourceStatusEventArgs e) { } However, the event method is being called twice.. once with my returned list, and once with the returned Int32 count. If I want to cast e.ReturnValue to the return List how do I differentiate between the count and select methods? I can do a e.ReturnValue.GetType().ToString() but that seems like a hack.

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• How can I get a nstableview to send an action when the user double-clicks an editable cell

  - by overcyn

  I am trying to emulate the behavior found in finder and itunes. Single click on a selected object edits it. Double click opens the object. I have set the doubleAction of the tableView but like it says in the documentation. "If the double-clicked cell is editable, this message isn’t sent and the cell is edited instead." I dont want this. Is there a way i can get that message sent even if the cell is editable? I really have no idea how to begin implementing this. Any general pointers would be appreciated.

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• Equivalent of c# 'as' command in c++?

  - by Sam

  In c# you can use as to convert a type or get null: Object o = Whatever(); String s = o as String; Is there a similar easy way to achieve this in c++? I'm using Visual Studio 2010, if thats important. [update] Remember, there is a very important difference between casting and using as. Casting (at least in c#) will throw an exception if the type does not match: Object o = null; String s = (String)o; // will crash.

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• C#, Using Custom Generic Collection faster with objects than List

  - by Kaminari

  Hello, I'm using for now List< to iterate through some object collection and find matching element, The problem is that object has only 2 significant values Name and Link (strings) but has some other values wich I dont want to compare. I'm thinkig about using something like HashSet (wich is exactly what I'm searching for - fast) from .NET 3.5 but target framework has to be 2.0. There is something called Power Collections here: http://powercollections.codeplex.com/ But maybe there is other way? If not, can you suggest me a suitable custom collection?

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• Initializing a value through a Session variable

  - by William Calleja

  I need to Initialize a value in a Javascript by using a c# literal that makes reference to a Session Variable. I am using the following code <script type="text/javascript" language="javascript" > var myIndex = <%= !((Session["myIndex"]).Equals(null)||(Session["myIndex"]).Equals("")) ? Session["backgroundIndex"] : "1" %>; However the code above is giving me a classic Object reference not set to an instance of an object. error. Why? Shouldn't (Session["myIndex"]).Equals(null) capture this particular error?

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• What's the best way to use hamcrest-AS3 to test for membership in an IList?

  - by Chris R

  I'm using Flex 3.3, with hamcrest-as3 used to test for item membership in a list as part of my unit tests: var myList: IList = new ArrayCollection(['a', 'b', 'c']).list; assertThat(myList, hasItems('a', 'b', 'c')); The problem is that apparently the IList class doesn't support for each iteration; for example, with the above list, this will not trace anything: for each (var i: * in myList) { trace (i); } However, tracing either an Array or an ArrayCollection containing the same data will work just fine. What I want to do is (without having to tear apart my existing IList-based interface) be able to treat an IList like an Array or an ArrayCollection for the purposes of testing, because that's what hamcrest does: override public function matches(collection:Object):Boolean { for each (var item:Object in collection) { if (_elementMatcher.matches(item)) { return true; } } return false; } Is this simply doomed to failure? As a side note, why would the IList interface not be amenable to iteration this way? That just seems wrong.

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• update_attributes with validations

  - by Timothy

  I have the following contrived example in Rails. I want to make sure the Garage model has at least one car with this. class Garage has_many :cars validate :at_least_one_car def at_least_one_car if cars.count == 0 errors.add_to_base("needs at least one car") end end end class Car belongs_to :garage end In my form I have a remove button that will set the hidden field _delete to true for an existing car. Let's say there is only one car object and I "delete" it in my form, if I do garage_object.update_attributes(params[:garage]), it will delete the car model and make the garage object invalid. Is there to a way to make it not update the attributes if it will make the model invalid?

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• Javascript Pointers question with Dates

  - by Mega Matt

  I noticed this situation in my code (unfortunately), and was able to duplicate it in my own JS file. So I have this code: var date1 = new Date(); // today var date2 = date1; date2 = date2.setDate(date2.getDate() + 1); // what is date1? After this code executes, date1 is today's date + 1! This harkens back to my undergrad days when I learned about pointers, and I guess I'm a little rusty. Is that what's happening here? Obviously I've moved the assignment away from date1, and am only modifying date2, but date1 is being changed. Why is this the case? Incidentally, after this code executes date2 is a long number like 1272123603911. I assume this is the number of seconds in the date, but shouldn't date2 still be a Date object? setDate() should return a Date object... Thanks for the help.

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• Firefox all but freezes during large file upload; Ajax progress bar infeasible; IE6 works fine

  - by Sean

  I want to provide a progress bar for my users who upload very large files. I did some reading and implemented what should be a pretty straightforward solution: I have a <form> element that contains an file input element; its target is set to the ID of a hidden iframe. On the server side, there's some Spring magic that attaches an object to the user's session; the progress of the upload can be queried from this object. After submitting the form, I start a repeating Ajax call using setInterval that queries the server for the percent-complete using the aforementioned session object. The call repeats every half-second, skipping the Ajax call if the previous call has not yet completed. I use the data from the call to update the width of an onscreen element. When the server call reports that the upload is complete, I clear the interval timer. I created a 100-megabyte file and uploaded it using my interface. This is using Firefox 3.6.3. What I found is that although the upload takes 20-25 seconds, the progress bar doesn't get updated until the very end. Moreover, the entire browser is basically frozen until the upload completes. I assumed that my method must be flawed, but I tried the same page using IE6, and was utterly amazed when it behaved as I had designed it to--the progress bar got updated every half second, and the whole upload only took about 15 seconds, much faster than Firefox. I don't have many add-ons installed, but I tried disabling Firebug and restarting my browser. This marginally improved the performance--I got perhaps a single additional progress bar update mid-upload--but still far from acceptable. Can anyone tell me what I can do to bring Firefox's performance up to the level of IE6? Ugh, I can't believe I actually typed that. EDIT: I just tried uploading a large file from a Firefox 3.6.3 browser on a different machine than the one that's running my web server, and it worked fine. Huh.

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• Retrieving Gtk::Widget's relative position: get_allocate() doesn't work

  - by a-v

  I need to retrieve the position of a Gtk::Widget relative to its parent, a Gtk::Table. Most sources (e.g. http://library.gnome.org/devel/gtk-faq/stable/x642.html) say that one needs to call Gtk::Widget::get_allocation(). However, the returned Gtk::Allocation object always contains x = -1, y = -1, width = 1, height = 1. I have to note that this happens before the Gtk::Table object is actually exposed and rendered. A call to show_all_children() or check_resize(), which I would expect to recalculate child widget geometry, doesn't help. What am I doing wrong? Thanks in advance.

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• how can I pass method Of one class to another class ?

  - by srikanth rongali

  I have a ClassA. in ClassA there is a method(-(void)parseData:). I have a ClassB which have ClassA object. And ClassB *aClassB is member variable of ClassA. In ClassB the code is aClassB = [[ClassB alloc]init]; [aClassB parseData]; I have ClassC. I need to use the method parseData of ClassB in ClassC. I think I can use the object created in ClassB of ClassA. How can I pass the method to ClassC ? Thank You.

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• Accessing Controls Values Before Finishing Page_Load

  - by userk

  Hi. I'm with a problem and want to know if someone can help me. I'm creating a table with some controls and I want to save all control values in every postback. As the controls are just defined after the page_load, I can't solve my problem this way: object o; protected void Page_Load(object sender, EventArgs e) { o = createObject(); Create_Table(); if (Page.IsPostBack) Save_Data(); } I thought I could execute Save_Data() at the begining of every postback event, but I think that should exist a better way to solve my problem. Thanks.

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• Correct approach to validate attributes of an instance of class

  - by systempuntoout

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

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• Why are Objective-C instance variables declared in an interface?

  - by Chase

  I'm just getting into Objective-C (Java is my primary OO language). Defining an object's instance variables in the interface instead of the class seems strange. I'm used to an interface being a public API definition with nothing besides method signatures (not counting constants here). Is there some reason that state is defined in an interface (even if it is private) and behaviour is defined in a class. It just seems odd that since objects are state+behavior that the definition would be split into two separate places. Is it a design benefit is some way? A pain in the rear issue that you are just forced to deal with in Objective-C? A non-issue, just different? Any background on why it's done this way? Or can you put object state in a class and I just haven't hit that part in my book yet?

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• What's the best way to return something like a collection of `std::auto_ptr`s in C++03?

  - by Billy ONeal

  std::auto_ptr is not allowed to be stored in an STL container, such as std::vector. However, occasionally there are cases where I need to return a collection of polymorphic objects, and therefore I can't return a vector of objects (due to the slicing problem). I can use std::tr1::shared_ptr and stick those in the vector, but then I have to pay a high price of maintaining separate reference counts, and object that owns the actual memory (the container) no longer logically "owns" the objects because they can be copied out of it without regard to ownership. C++0x offers a perfect solution to this problem in the form of std::vector<std::unique_ptr<t>>, but I don't have access to C++0x. Some other notes: I don't have access to C++0x, but I do have TR1 available. I would like to avoid use of Boost (though it is available if there is no other option) I am aware of boost::ptr_container containers (i.e. boost::ptr_vector), but I would like to avoid this because it breaks the debugger (innards are stored in void *s which means it's difficult to view the object actually stored inside the container in the debugger)

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• how to access a different movieclip within the flash in AS3

  - by Pieter888

  I've been trying to learn Action Script 3 the past few weeks, making tiny interactive games to learn the basics. I stumble upon a problem every now and then but most of the times google helps me out. But this problem has got me stuck so please help: The main stage contains two objects(movieclips), the player and a wall. The player has got his own code so when I drag in the player object I don't have to write any code into the main stage to be able to move the player. This all worked pretty well and I now wanted to add the wall so the player actually has something to bounce into. Now here is the problem, I want to check if the player touches the wall, I've done this before but that was when I used the main stage as my coding playground instead of putting the code in movieclips. How can I check if the player hits the wall within the movement code of the player object?

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• Choose between multiple options with defined probability

  - by Sijin

  I have a scenario where I need to show a different page to a user for the same url based on a probability distribution, so for e.g. for 3 pages the distribution might be page 1 - 30% of all users page 2 - 50% of all users page 3 - 20% of all users When deciding what page to load for a given user, what technique can I use to ensure that the overall distribution matches the above? I am thinking I need a way to choose an object at "random" from a set X { x1, x2....xn } except that instead of all objects being equally likely the probability of an object being selected is defined beforehand.

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• simple JQuery example is causing me troubles for unknown reason

  - by cerr

  I'm relatively new to JQuery and would like to try something. I just followed a simple tutorial to start up with on http://docs.jquery.com/Tutorials:Getting_Started_with_jQuery So I specified my script in the : <script type="text/javascript"> $(document).ready(function() { $("a").click(function() { alert("Hello world!"); }); }); </script> and included a test link in the : <a href="">Link</a> however, when I refresh thet document my browser keeps saying TypeError: Property '$' of object [object Window] is not a function which I can understand for "normal" JavaScript but I believe this kind of function is new in JQuery. Can someone assist mer here, please? links:http://wittmerperformance.com/site/

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• Silverlight Windows Phone 7: Load Images From URL

  - by Lennie De Villiers

  Hi, I got the code below that is trying to load an image from the web into an Image control, when I run it I get an error on the given line that no network access is allowed: private void button1_Click(object sender, RoutedEventArgs e) { WebClient webClientImgDownloader = new WebClient(); webClientImgDownloader.OpenReadCompleted += new OpenReadCompletedEventHandler(webClientImgDownloader_OpenReadCompleted); webClientImgDownloader.OpenReadAsync(new Uri("http://dilbert.com/dyn/str_strip/000000000/00000000/0000000/000000/80000/5000/100/85108/85108.strip.print.gif", UriKind.Absolute)); } void webClientImgDownloader_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { BitmapImage bitmap = new BitmapImage(); bitmap.SetSource(e.Result); // ERROR HERE! image1.Source = bitmap; } Silverlight for Windows Phone 7

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• Compiler error when using abstract types

  - by Dylan

  I'm trying to implement a "protocol helper" trait that is responsible for matching up Prompts and Responses. The eventual goal is to have an object that defines the various Prompt and Response classes as subclasses of a sealed trait, then have a class that mixes in the ProtocolSupport trait for that Protocol object. The problem is that my current approach won't compile, even though I'm fairly sure it should. Here's a distilled version of what I've got: trait Protocol { type Response type Prompt <: BasePrompt trait BasePrompt { type Data def validate(response: Response): Validated[Data] } } trait ProtocolSupport[P <: Protocol] { def foo(prompt: P#Prompt, response: P#Response) = { // compiler error prompt.validate(response) } } The compiler doesn't like the response as an argument to prompt.validate: [error] found : response.type (with underlying type P#Response) [error] required: _4.Response where val _4: P [error] prompt.validate(response) [error] ^ This isn't very helpful.. it seems to say that it wants a P.Response but that's exactly what I'm giving it, so what's the problem?

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