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  • What is dbReferenceProperty?

    - by user246114
    Hi, In the python app engine docs, I see something called dbReferenceProperty. I can't understand what it is, or how it's used. I'm using the java interface to app engine, so I'm not sure if there's an equivalent. I'm interested in it because it sounds like some sort of pseudo-join, where we can point a property of a class to some other object's value - something like if we had: class User { private String mPhotoUrl; private String mPhone; private String mState; private String mCountry; .. etc .. } class UserLite { @ReferenceProperty User.mPhotoUrl; private String mPhotoUrl; } then if we had to update a User object's mPhotoUrl value, the change would somehow propagate out to all UserLite instances referencing it, rather than having to update every UserLite object instance manually, Thanks

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  • Why does the compiler give an ambiguous invocation error when passing inherited types?

    - by Matt Mitchell
    What is happening in the C# compiler to cause the following ambiguous invocation compilation error? The same issue applies to extension methods, or when TestClass is generic and using instance rather than static methods. class Type1 { } class Type2 : Type1 {} class TestClass { public static void Do<T>(T something, object o) where T : Type1 {} public static void Do(Type1 something, string o) {} } void Main() { var firstInstance = new Type1(); TestClass.Do(firstInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(firstInstance, "Test"); // Calls Do<T>(T, string) var secondInstance = new Type2(); TestClass.Do(secondInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(secondInstance, "Test"); // "The call is ambiguous" compile error }

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  • that, self or me — which one to prefer in JavaScript?

    - by Török Gábor
    While coding JavaScript sometimes you store the reference of object this in a local variable for different purposes (to set proper scope, to help code obfuscators, etc.). There are coders who prefer aliasing this to that to make it obvious its intention. Other guys use self since it's pointing to the object itself. I even saw source codes where me held the reference and it still makes sense. Certainly there are other ones. Which one should I prefer? Is there a convention on which to use or is it only the matter of taste.

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  • Polymorphic behavior not being implemented

    - by Garrett A. Hughes
    The last two lines of this code illustrate the problem: the compiler works when I use the reference to the object, but not when I assign the reference to an array element. The rest of the code is in the same package in separate files. BioStudent and ChemStudent are separate classes, as well as Student. package pkgPoly; public class Poly { public static void main(String[] arg) { Student[] stud = new Student[3]; // create a biology student BioStudent s1 = new BioStudent("Tom"); // create a chemistry student ChemStudent s2 = new ChemStudent("Dick"); // fill the student body with studs stud[0] = s0; stud[1] = s1; // compiler complains that it can't find symbol getMajor on next line System.out.println("major: " + stud[0].getMajor() ); // doesn't compile; System.out.println("major: " + s0.getMajor() ); // works: compiles and runs correctly } }

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  • NoSuchMethodException while using JAVA Reflection

    - by Appps
    Hi I'm trying to use reflection to invoke a method and update the setter value of that method. But I'm getting NoSuchMethodException while ivoking that method. com.test.Test.setAddress1(java.lang.Double) .But I've this method defined in my Class. Is the problem with my code. Can someone please help me? Thanks in advance. I've my code below. Class[] doubleArrayParamTypes = new Class[ 1 ]; doubleArrayParamTypes[ 0 ] = Double.class; Class class=Class.forName( "com.test.Test"); Object voObject = class.newInstance(); String data="TestData"; performMapping(class,"setAddress1",doubleArrayParamTypes ,voObject,data); /* Reflection to set the data */ private void performMapping(Class class,String methodName,Class[] clazz,Object voObject,Object data) { class.getMethod( "set" + methodName, clazz ).invoke( voObject, data ); }

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  • CoreData Model Objects for API

    - by theiOSguy
    I am using CoreData in my application. I want to abstract out all the CoreData related stuff as an API so that the consume can use the API instead of directly using CoreData and its generated model objects. CoreData generates the managed objects model as following @interface Person : NSManagedObject @end I want to define my API for example MyAPI and it has a function called as createPerson:(Person*)p; So the consumer of this createPerson API needs to create a Person data object (like POJO in java world) and invoke this API. But I cannot create Person object using Person *p = [Person alloc] init] because the designated initializer for this Person model created by CoreData does not allow this type of creation. So should I define corresponding user facing data object may be PersonDO and this API should take that instead to carry the data into the API implementation? Is my approach right? Any expert advise if design the API this way is a good design pattern?

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  • C++11: thread_local or array of OpenCL 1.2 cl_kernel objects?

    - by user926918
    I need to run several C++11 threads (GCC 4.7.1) parallely in host. Each of them needs to use a device, say a GPU. As per OpenCL 1.2 spec (p. 357): All OpenCL API calls are thread-safe75 except clSetKernelArg. clSetKernelArg is safe to call from any host thread, and is safe to call re-entrantly so long as concurrent calls operate on different cl_kernel objects. However, the behavior of the cl_kernel object is undefined if clSetKernelArg is called from multiple host threads on the same cl_kernel object at the same time. An elegant way would be to use thread_local cl_kernel objects and the other way I can think of is to use an array of these objects such that i'th thread uses i'th object. As I have not implemented these earlier I was wondering if any of the two are good or are there better ways of getting things done. TIA, S

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  • how to debug a WCF service once it's out of dev env

    - by ffc
    hi, I have a WCF service that i've been able to communicate with fine while it's hosted locally. I have it deployed to a web server in IIS now, and I can get the wsdl file without error by navigating to http://site.com:8000/service/servicename.svc?wsdl in trying to test this, i've created a console app and was able to successfully add a service reference to this. But when I try to run a Get() method on the service reference, it just hangs with no response. How can I begin to debug this? Thanks!

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  • Use CSS (and maybe JavaScript) to make an element be square (or maintain a specific aspect ratio)

    - by David Pfeffer
    I have a div that I want to have the following characteristics: Width = 50% of its parent element Height equal to whatever it needs to be in order to maintain a certain aspect ratio. I need to use percentages because the object will resize left-right when the browser is resized. I want the object to be resized top-bottom to ensure the object maintains the same aspect ratio. I don't think there's any way to use pure CSS to do this, but does anyone know of a way? Alternatively, is there an easy JavaScript way to do this? (JQuery is fine.)

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  • When is NSEnumerator finished?

    - by samfu_1
    How do we know when enumeration is finished? The docs say: the return value of nextObject is nil when all objects have been enumerated. I was hoping to implement some "delegate-like" behavior whereby ... if (nextObject == nil) { do something because we're done! } But I see there is no such thing as: enumerationDidFinish: where in the following block could I check for the enumerator to be complete? NSArray *anArray = // ... ; NSEnumerator *enumerator = [anArray objectEnumerator]; id object; while ((object = [enumerator nextObject])) { // do something with object... }

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  • JSF/HTML - Add a java applet to web page programmaticly.

    - by Ben
    Hi, Theres a web page i'm making which content is very dynamic and so I'm building it from inside the backing bean. I would like to add a java applet to the web page but I could not find the Java Object to correspond to the <applet> tag. So My questions are - What is the JAVA Object for an applet? How did you find it? (For similar future searches) Thanks! P.S - Just to be clear. An example: <h:PanelGroup> would be HtmlPanelGroup as a java object.

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  • how to force nhibernate to set the foreign key of the child item?

    - by npeBeg
    i have a collection in the mapping: <bag name="Values" cascade="all-delete-orphan" lazy="false" inverse="true"> <key column="[TemplateId]"/> <one-to-many class="MyNamespace.Value, MyLib"/> </bag> the Value object has a foreign key [TemplateId]. both entities has their generator set to "identity". when i call session.Save() for the parent Template object, the Value objects has their [TemplateId] (the foreign key) set to zero, so an SQL exception appears. how do i forse nhibernate to set the FK value for the child items to the value of the inserted parent object?

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  • How do I use SPMemember.ID property to get User or Group

    - by Jason
    I have to write a utility to enumerate and manage the owners of groups within a SharePoint site. I know I can use the Groups property of the SPWeb object to retrieve a collection of groups. And I know I can use the Owner property of the group to get back the owner. My problem is that I do not know what to do next. The SPGroup.Owner property returns a SPMember object. The member object has one property called ID that returns the unique ID (an integer) of the member. What I cannot seem to find information on is how to use that integer value to determine if the member is a User or a Group and how to get back additional details (say the name). Any ideas? Thanks.

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  • Accessing CoreData relationships

    - by georgeliquor
    I have the following core data model with two entities: entity "item" which holds name, date, description and a to many relationship "image". image is optional. entity "image" holds url, name and relationship to one item. I load the executed Fetchrequest into this NSArray "entityArray" This is what I do to display my data in a UITableView for example to display title in main cell: NSManagedObject *object = (NSManagedObject *)[entityArray objectAtIndex:indexPath.row]; cell.textLabel.text=[object valueForKey:@"title"]; Now I have no clue how to access my relationship image ([object valueForKey:@"image"]), because it contains more than just a string.

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  • how to create english language dictionary application with python (django)?

    - by sintaloo
    Hi All, I would like to create an online dictionary application by using python (or with django). It will be similar to http://dictionary.reference.com/. My question is (1) Are there any existing open source python package or modules or application which implements this functionality that I can use or study from? (2) If the answer to the first question is NO. which algorithm should I follow to create such web application? Can I simply use the python built-in dictionary object for this job? so that the dictionary object's key will be the english word and the value will be the explanation. is this OK in term of performance? OR Do I have to create my own Tree Object to speed up the search? or any existing package which handles this job properly? Thank you very much.

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  • How to link .lib library in linux

    - by giga
    I'm pretty new to c programming and want to port a windows c application to linux. My code uses a .lib file va_g729.lib - is it possible to use the same library in Linux and compile it with gcc? All my .c and .h files along with the one .lib files are in the same directory. What I'm doing now is executing this command in the directory: gcc *.c -lm and I get following errors: lbcodec2.c:(.text+0xa6b): undefined reference to `va_g729a_init_encoder' lbcodec2.c:(.text+0xa83): undefined reference to `va_g729a_encoder' collect2: error: ld returned 1 exit status Is it possible to link the .lib file and compile with gcc? Thanks.

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  • thread destructors in C++0x vs boost

    - by Abruzzo Forte e Gentile
    Hi All These days I am reading the pdf Designing MT programs . It explains that the user MUST explicitly call detach() on an object of class std::thread in C++0x before that object gets out of scope. If you don't call it std::terminate() will be called and the application will die. I usually use boost::thread for threading in C++. Correct me if I am wrong but a boost::thread object detaches automatically when it get out of scope. Is seems to me that the boost approach follow a RAII principle and the std doesn't. Do you know if there is some particular reason for this? Kind Regards AFG

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  • What are the disadvantages of using a StringBuilder?

    - by stickman
    I know that StringBuilder is more efficient than a normal string when processing code which modifies the string value a lot because although strings act like value types, they are actually reference, which makes them immutable so every time we change it, we need to create a new reference in memory. My question is that, why doesn't .NET just use stringBuilder by default? There must be some disadvantages of it over just using String. Can anyone tell me what they are? The only thing I can think of is perhaps it is a heavier object and it takes more time to instantiate so if you aren't changing the string too much, this would override the benefits of StringBuilder

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  • 'Caching' a large table in ASP.NET

    - by TheNewGuy
    I understand that each page refresh, especially in 'AjaxLand', causes my back-end/code-behind class to be called from scratch... This is a problem because my class (which is a member object in System.Web.UI.Page) contains A LOT of data that it sources from a database. So now every page refresh in AjaxLand is causing me to making large backend DB calls, rather than just to reuse a class object from memory. Any fix for this? Is this where session variables come into play? Are session variables the only option I have to retain an object in memory that is linked to a single-user and a single-session instance?

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  • Reason for unintuitive UnboundLocalError behaviour 2

    - by Jonathan
    Following up on Reason for unintuitive UnboundLocalError behaviour (I will assume you've read it). Consider the following Python script: def f(): # a+=1 # 1 aa=a aa+=1 # b+='b' # 2 bb=b bb+='b' c[0]+='c' # 3 c.append('c') cc=c cc.append('c') # 4 a=1 b='b' c=['c'] f() print a print b print c The result of the script is: 1 b ['cc', 'c', 'c'] The commented out lines (marked 1,2) are lines that would through an UnboundLocalError and the SO question I referenced explains why. However, the line marked 3 works! By default, lists are copied by reference in Python, therefore it's understandable that c changes when cc changes. But why should Python allow c to change in the first place, if it didn't allow changes to a and b directly from the method's scope? I don't see how the fact that by default lists are copied by reference in Python should make this design decision inconsistent. What am I missing folks?

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  • IndexedDB and Relationships

    - by Josh Johnson
    Can I create relationships between my object stores in IndexedDB? For example, I have two object stores: artist and album. An artist has a one-to-many relationship with an album. album.artistId relates the album to artist.id. I'm thinking along the lines of Hibernate here. I would like to do a query for artists and have the albums belonging to that artist returned as an array called artists on the album object. artist.albums = [];

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  • Global Import/using Aliasing in .NET

    - by Josh Stodola
    Using import aliasing in a single class, we can reference class library namespaces by assigning our own custom alias like this: ' VB Imports Db = Company.Lib.Data.Objects // C# using Db = Company.Lib.Data.Objects; And then we are able to reference the classes inside of Company.Lib.Data.Objects by using the Db alias that we assigned. Is it possible to do this at the global level so that the alias is applied to the entire solution instead of the given file? Currently, we are working with web applications, so I was hoping we could add something to web.config, but I am also interested in whether or not this is possible with windows forms, console apps, and/or class libraries.

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  • How to ensure consistency of enums in Java serialization?

    - by Uri
    When I serialize an object, I can use the serialVersionUID mechanism at the class level to ensure the compatibility of the two types. However, what happens when I serialize fields of enum values? Is there a way to ensure that the enum type has not been manipulated between serialization and deserialization? Suppose that I have an enum like OperationResult {SUCCESS, FAIL}, and a field called "result" in an object that is being serialized. How do I ensure, when the object is deserialized, that result is still correct even if someone maliciously reversed the two? (Suppose the enum is declared elsewhere as a static enum) I am wondering out of curiosity - I use jar-level authentication to prevent manipulation.

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  • Iphone UI Size / Layout Resource?

    - by blindJesse
    Is anyone aware of a website or download to reference for the size of UI elements or standard iphone interface stuff? What I mean is something that gives the height of elements like the status bar, tab bar, navigation bar, default tableviewcell height (and such things as width of accessory view, indentation, etc), default icon sizes, default font sizes for UI elements (if they need to be mimicked, for instance), etc etc etc. It's amazing how many times I have to go back to find a reference or estimate the size and position of a standard element. It seems like it would be an invaluable resource that could fit on a printed page or two.

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  • How to map a virtual directory to a website in VS?

    - by salvationishere
    I am developing a C# VS 2008 website, trying to add a Master file. I created a virtual directory in IIS housing the "Master" folder, containing the Master files. Now how do I reference these files from my website in VS? One problem is I do not know where I need to publish this Master folder to. Other problem is I do not know how to reference this Master file in my aspx Page directive. FYI, this master folder is physically located outside of c:\inetpub\ in a totally separate file location. Is this a problem?

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