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  • Graceful Degradation with JSON.Parse

    - by Steve
    If a browser doesn't support JSON.parse, would it make sense to include json.js and call parseJSON in lieu? So the code would looks something like: var z; if (JSON.parse) z = JSON.parse(yada); else z = JSON.parseJSON(yada);

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  • Dynamic Dispatch without Virtual Functions

    - by Kristopher Johnson
    I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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  • C++ superclass constructor calling rules

    - by levik
    What are the C++ rules for calling the superclass constructor from a subclass one?? For example I know in Java, you must do it as the first line of the subclass constructor (and if you don't an implicit call to a no-arg super constructor is assumed - giving you a compile error if that's missing).

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  • cocos2d 2.x scene retainCount

    - by Shefy Gur-ary
    I'm pushing a scene to the game I'm working on, after pressing a button in the main menu. This scene is a gameplayScene which should have two layers ad childs: boardLayer and hudLayer. for now I'm testing with the boardLayer, I'm using block to call the gameplayScene to close both itself and the boardLayer, but by the time I get there the retain count of both layer is 3 (seems to be increasing after setting the block to 2, and I'm not sure when it is going up to 3) What cause this, and how should it be handled?

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  • Unable to read data from the transport connection: the connection was closed

    - by webdreamer
    The exception is Remoting Exception - Authentication Failure. The detailed message says "Unable to read data from the transport connection: the connection was closed." I'm having trouble with creating two simple servers that can comunicate as remote objects in C#. ServerInfo is just a class I created that holds the IP and Port and can give back the address. It works fine, as I used it before, and I've debugged it. Also the server is starting just fine, no exception is thrown, and the channel is registered without problems. I'm using Forms to do the interfaces, and call some of the methods on the server, but didn't find any problems in passing the parameters from the FormsApplication to the server when debugging. All seems fine in that chapter. public ChordServerProgram() { RemotingServices.Marshal(this, "PADIBook"); nodeInt = 0; } public void startServer() { try { serverChannel = new TcpChannel(serverInfo.Port); ChannelServices.RegisterChannel(serverChannel, true); } catch (Exception e) { Console.WriteLine(e.ToString()); } } I run two instances of this program. Then startNode is called on one of the instances of the application. The port is fine, the address generated is fine as well. As you can see, I'm using the IP for localhost, since this server is just for testing purposes. public void startNode(String portStr) { IPAddress address = IPAddress.Parse("127.0.0.1"); Int32 port = Int32.Parse(portStr); serverInfo = new ServerInfo(address, port); startServer(); //node = new ChordNode(serverInfo,this); } Then, in the other istance, through the interface again, I call another startNode method, giving it a seed server to get information from. This is where it goes wrong. When it calls the method on the seedServer proxy it just got, a RemotingException is thrown, due to an authentication failure. (The parameter I'll want to get is the node, I'm just using the int to make sure the ChordNode class has nothing to do with this error.) public void startNode(String portStr, String seedStr) { IPAddress address = IPAddress.Parse("127.0.0.1"); Int32 port = Int32.Parse(portStr); serverInfo = new ServerInfo(address, port); IPAddress addressSeed = IPAddress.Parse("127.0.0.1"); Int32 portSeed = Int32.Parse(seedStr); ServerInfo seedInfo = new ServerInfo(addressSeed, portSeed); startServer(); ChordServerProgram seedServer = (ChordServerProgram)Activator.GetObject(typeof(ChordServerProgram), seedInfo.GetFullAddress()); // node = new ChordNode(serverInfo,this); int seedNode = seedServer.nodeInt; // node.chordJoin(seedNode.self); }

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  • how to use @ in python.. and the @property

    - by zjm1126
    this is my code: def a(): print 'sss' @a() def b(): print 'aaa' b() and the Traceback is: sss Traceback (most recent call last): File "D:\zjm_code\a.py", line 8, in <module> @a() TypeError: 'NoneType' object is not callable so how to use the '@' thanks updated class a: @property def b(x): print 'sss' aa=a() print aa.b it print : sss None how to use @property thanks

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  • Run shell command from jar?

    - by phineas
    The usual way to call a shell command from java is something like that: Process process = Runtime.getRuntime().exec(command); and works usually fine. But now I've exported my project to an executable jar file and callig shell commands doesn't work any more. Are there any explanations, solutions or workarounds for this problem? phineas -- edit: even keyboard interrupts (ctrl+c; ctrl+d) aren't recognized. terminal input won't work after killing java

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  • Does anyone know of a spell check library that underlines text?

    - by Icono123
    Does anyone know of a C# spell check library that would underline misspelled works in a windows form text box? In the past, I've used NetSpell and works great if users use the dialog box. I'm thinking I might be able to automatically call the spell check while text is being updated and underline the text. Anyone have any good ideas on what would be the best way to go about doing it?

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  • domain modeling naming problem

    - by cherouvim
    Hello There are some simple entities in an application (e.g containing only id and title) which rarely change and are being referenced by the more complex entities of the application. These are usually entities such as Country, City, Language etc. How are these called? I've used the following names for those in the past but I'm not sure which is the best way to call them: reference data lookup values dictionaries thanks

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  • Calculating volume for sphere in c++

    - by Crystal
    This is probably an easy one, but is the right way to calculate volume for a sphere in c++. My getArea() seems to be right, but when I call getVolume() it doesn't output the right amount. With a sphere of radius = 1, it gives me the answer of pi, which is incorrect: double Sphere::getArea() const { return 4 * Shape::pi * pow(getZ(), 2); } double Sphere::getVolume() const { return (4 / 3) * Shape::pi * pow(getZ(), 3); }

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  • Reopening serial port fails if not closed properly with CloseHandle

    - by superg
    I am working with USB device on Windows that is seen as a virtual serial port. I can communicate with the device using CreateFile and ReadFile functions, but in some cases my application does not call CloseHandle (when my application in development crashes). After that all calls to CreateFile fail (ERROR_ACCESS_DENIED), and the only solution is to log in to my computer again. Is there any way to force closing the open handle (or reopening) programmatically?

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  • Can I make a LaTeX macro 'return' a filename?

    - by drfrogsplat
    I'm writing my thesis/dissertation and since its an on-going work I don't always have the actual images ready for the figures I put into my document, but for various reasons want to automatically have it substitute a dummy figure in place when the included graphics file doesn't exist. E.g. I can do something like \includegraphics[width=8cm]{\chapdir/figures/fluxcapacitor} (where \chapdir is a macro for my 'current' chapter directory, e.g. \def\chapdir{./ch_timetravel} and if there's no ./ch_timetravel/figures/fluxcapacitor.jpg it'll insert ./commands/dummy.jpg instead. I've structured my macros (perhaps naïvely?) so that I have a macro (\figFileOrDummy) that determines the appropriate file to include by checking if the argument provided to it exists, so that I can call \includegraphics[properties]{\figFileOrDummy{\chapdir/figures/fluxcapacitor}}. Except I'm getting various errors depending on how I try to call this, which seem to suggest that I'm approaching the problem in a fundamentally flawed way as far as 'good LaTeX programming' goes. Here's the macro to check if the file exists (and 'return' either filename or the dummy filename): \newcommand{\figFileOrDummy}[1]{% % Figure base name (no extension) to be used if the file exists \def\fodname{#1}% \def\dummyfig{commands/dummy}% % Check if output is PS (.EPS) or PDF (.JPG/.PDF/.PNG/...) figures \ifx\pdfoutput\undefined% % EPS figures only \IfFileExists{\fodname.eps}{}{\def\fodname{\dummyfig}}% \else% % Check existence of various extensions: PDF, TIF, TIFF, JPG, JPEG, PNG, MPS \def\figtest{0}% flag below compared to this value \IfFileExists{\fodname.pdf}{\def\figfilenamefound{1}}{\def\figfilenamefound{0}}% \IfFileExists{\fodname.jpg}{\def\figfilenamefound{1}}{}% \IfFileExists{\fodname.png}{\def\figfilenamefound{1}}{}% % and so on... % If no files found matching the filename (flag is 0) then use the dummy figure \ifx\figfilenamefound\figtest% \def\fodname{\dummyfig}% \fi% \fi% % 'return' the filename \fodname% }% Alternatively, here's a much simpler version which seems to have similar problems: \newcommand{\figFileOrDummy}[1]{% \def\dummyfig{commands/dummy}% \dummyfig% } The \def commands seems to be processed after the expansion of the macro they're trying to define, so it ends up being \def {commands/dummy}... (note the space after \def) and obviously complains. Also it seems to treat the literal contents of the macro as the filename for \includegraphics, rather than resolving/expanding it first, so complains that the file '\def {commands/dummy}... .png' doesn't exist.. I've tried also doing something like \edef\figfilename{\figFileOrDummy{\chapdir/figures/fluxcapacitor}} to try to force it to make \figfilename hold just the value rather than the full macro, but I get an Undefined control sequence error complaining the variables I'm trying to \def in the \figFileOrDummy macro are undefined. So my question is either How do I make this macro expand properly?; or If this is the wrong way of structuring my macros, how should I actually structure such a macro, in order to be able to insert dummy/real figures automatically?; or Is there a package that already handles this type of thing nicely that I've overlooked? I feel like I'm missing something pretty fundamental here...

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  • why the class of subclass is superclass

    - by Raj
    def singleton_class class << self self end end end class Human proc = lambda { puts 'proc says my class is ' + self.name.to_s } singleton_class.instance_eval do define_method(:lab) do proc.call end end end class Developer < Human end Human.lab # class is Human Developer.lab # class is Human ; oops Why Developer.lab is reporting that it is Human ?

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  • How to determine whether a spread-sheet cell contains a date, or a real number?

    - by Everyone
    When a cell in a spreadsheet contains a simple date (mm/dd/yyyy) the poi API flags the cell-type as 'numeric'. This is probably because spreadsheets ( IMO ) historically recognize only strings and real numbers. It is possible to hard-code the cell-index, and use it conditionally to call 'getDateCellValue'. But this feels like a hack. What other ways are there in the poi API to determine whether the content in a cell is a Date rather than a real number?

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  • why inner class doesn't compile..?

    - by Vincenzo
    This is my code: #include <algorithm> class A { void f() { struct CompareMe { bool operator() (int i, int j) { return i < j; } } comp; int a[] = {1, 2, 3, 4}; int found = std::min_element(a[0], a[3], comp); } } Error message: no matching function for call to ‘min_element(int&, int&, A::f()::CompareMe&) What am I doing wrong?

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  • calling a function from static function

    - by iSight
    Hi, how can i call a function which computes with input parameters from an another static function. say, class X { static void xyz(); static int pqr(int, int); }; static X::void xyz() { ...pqr(10,20); } int X::pqr(int t1, int t2) { return t1*t2; }

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  • Top 10 Graph Charting Tools

    - by Daniel
    When charting information what is the best tool to use? Of course we call know if excel, but is there something better then that? I know if things like Google Chart Tools: http://code.google.com/apis/charttools/ But want to know what the best tools out there are.

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  • How to pass username and password for authentication in URL?

    - by Maggie
    Hi there. I need to pass the user name and password in the URL for a REST web services call. I know that if I pass it this way in Firefox, it works: https://{UserName}:{Password}@api.opsourcecloud.net/oec/0.9/myaccount Is there a proper way to pass user name and password aside from the above example? It's a Spring Security Context?

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  • vim unicode bufread/bufwrite script

    - by anon
    Problem: I want my unicode characters to be stored on disk as (rather tan utf8/16 encoding) \u#### However, I want them dispalyed as unicode characters when opened up in vim. I think the easiest way to acheive this is some bufopen/bufwrite script that automatically: on opening, convert \u#### to unicode character on writing, convert unicode characters into \u#### However, I don't know what functions to call to make this happen. Can someone lend a hand? Thanks!

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