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  • C++ - checking if a class has a certain method at compile time

    - by jetwolf
    Here's a question for the C++ gurus out there. Is there a way to check at compile time where a type has a certain method, and do one thing if it does, and another thing if it doesn't? Basically, I have a template function template <typename T> void function(T t); and I it to behave a certain way if T has a method g(), and another way if it doesn't. Perhaps there is something that can be used together with boost's enable_if? Something like this: template <typename T> enable_if<has_method<T, g, void ()>, void>::type function(T t) { // Superior implementation calling t.g() } template <typename T> disable_if<has_method<T, g, void ()>, void>::type function(T t) { // Inferior implementation in the case where T doesn't have a method g() } "has_method" would be something that preferably checks both that T has a method named 'g', and that the method has the correct signature (in this case, void ()). Any ideas?

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  • Lifetime of implicitly casted temporaries

    - by Answeror
    I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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  • background picture for textview

    - by AndyAndroid
    Hi, I have a textview and a nine-patch image. Assigning this image in the xml editor to the tag "background" works as desired. Now I want to set this image dynamically in the coding, I thought myTextView.setBackgroundDrawable(mydrawable); would be the right thing to do. My png is in res/drawable. The API says that mydrawable needs to be an object of type drawable R.drawable.myninepatch is of type int. So my problem is that I have to convert from that int to a drawable somehow. Then I thought I can use a constructor NinePatchDrawable mydrawable = new NinePatchDrawable(); But I am again not able to construct such an object. Anyone an idea? Thanks.

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  • Getting the value from an array in the model in rails

    - by slythic
    Hi all, I have a relatively simple problem. I have a model named Item which I've added a status field. The status field will only have two options (Lost or Found). So I created the following array in my Item model: STATUS = [ [1, "Lost"], [2, "Found"]] In my form view I added the following code which works great: <%= collection_select :item, :status, Item::STATUS, :first, :last, {:include_blank => 'Select status'} %> This stores the numeric id (1 or 2) of the status in the database. However, in my show view I can't figure out how to convert from the numeric id (again, 1 or 2) to the text equivalent of Lost or Found. Any ideas on how to get this to work? Is there a better way to go about this? Many thanks, Tony

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  • Is it possible to create a jdbc connection without a password (using postgresql 'trust')?

    - by mojones
    I am using jdbc to connect to a postgresql database in a java application (actually the app is written in Groovy). I have postgresql set up to use the 'trust' authentication method. Is it possible to open a jdbc connection without specifying a password? When I try to use the normal constructor with a blank password, it fails with Exception in thread "Thread-2" org.postgresql.util.PSQLException: FATAL: password authentication failed for user "myuser" Even though, from the command line, this works fine psql -U myuser mydatabase Welcome to psql 8.3.5, the PostgreSQL interactive terminal. Type: \copyright for distribution terms \h for help with SQL commands \? for help with psql commands \g or terminate with semicolon to execute query \q to quit

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  • Possible Conflict with Class name & Property Name?

    - by coffeeaddict
    If you have a namespace that contains a property in ClassA and a class that has the name of that Property somewhere else in your project and both are in the same namespace this won't cause conflicts will it? So lets say I have a class named Car namespace Dealer { class Vehicle { // the main class that defines vehicle, so this is Dealer.Vehicle (Vehicle.cs) } } and a property over in some other class namespace Dealer { class Dealer { public Vehicle Vehicle { get { return _vehicle; } } } } so for the second it is really this for the property public Dealer.Vehicle Vehicle { get { return _car; } } so now you have Dealer.Vehicle and Dealer.Dealer.Vehicle. Wondering of that would cause a conflict ever. If both those classes are in the same namespace and

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  • How to implement message passing in GNUradio?

    - by xuandl
    I need to implement message passing, my idea is to make some sort of message source (I inherit from public gr_sync_block) that works as a controller for another block (it has to send a message each 6 minutes). I read that is necessary to inherit from gnuradio::block -and by the way, installing grextras is mandatory-. In the .h file I added the #include and inherited from block"class JDFM_API jdfm_control : public gr_sync_block, public gnuradio::block". I know that I have redefine some things like the gnuradio::block constructor but I dont know what msg_signature is, I also don't get the relation between block's parameters and work parameter, the last thing that I am not sure is if I still can use gnuradio-companion if I create a block like this. I haven't been able to find a simple example of messages implementation. If anyone can guide me or show me an example, it would be awesome. Thanks in advance.

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  • What could possibly cause this error(when declaring an object inside a class) ? //noobie question

    - by M4design
    I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info' I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. Thanks. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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  • WordPress theme blog not displaying well in FireFox-how to fix?

    - by rpd
    Hi I have recently made a new WordPress theme (named {cssgroundup}) which I am using on my blog at www.richard-dickinson.com It is only a basic WP theme for my personal use as I am quite new to the WordPress platform (?). It is a work in progress (as is the blog content!) however it displays alright in IE browser but not so well in FireFox. Can someone help me edit it so it displays properly in most browsers or advise me how I can fix this please? I have asked for help at wordpress.org forums but haven't yet had any help! I can post stylesheet code & theme.php code here if required. I look forward to helpful replies, many thanks

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  • ClassNotFoundException (HqlToken) when running in WebLogic

    - by dave
    I have a .war file for an application that normally runs fine in Jetty. I'm trying to port the application to run in WebLogic, but at startup I'm getting these exceptions: ERROR:Foo - Error in named query: findBar org.hibernate.QueryException: ClassNotFoundException: org.hibernate.hql.ast.HqlToken [from Bar] at org.hibernate.hql.ast.HqlLexer.panic(HqlLexer.java:80) at antlr.CharScanner.setTokenObjectClass(CharScanner.java:340) at org.hibernate.hql.ast.HqlLexer.setTokenObjectClass(HqlLexer.java:54) at antlr.CharScanner.<init>(CharScanner.java:51) at antlr.CharScanner.<init>(CharScanner.java:60) at org.hibernate.hql.antlr.HqlBaseLexer.<init>(HqlBaseLexer.java:56) at org.hibernate.hql.antlr.HqlBaseLexer.<init>(HqlBaseLexer.java:53) at org.hibernate.hql.antlr.HqlBaseLexer.<init>(HqlBaseLexer.java:50) ... What's the best way to fix this? I'm using Hibernate 3.3.1.GA and WebLogic 10.3.2.0.

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  • How do I reference the other object in django models

    - by UserZero
    Hi, first post here.In Django, I want to have many files be associated with a particular model, so I'm doing a seperate model called files and have model 'A' 'have many' files. But I want my files to be saved in director named by model 'A'. So For example I want something like this: class Show(models.Model): name = models.CharField() showfolder = models.FilePathField() class Episode(models.Model): show = models.ForeignKey(Show) name = models.CharField() files = models.ManyToManyField(mp3) class Mp3(models.Model): file = FileField(upload_to=Episode.show.showfolder) So hopefully that last line expresses what I WANT it to do(get the folder name from Show object associated with the episode). The question is how would I really write that?(besides jumping through hoops in the controller.) Thanks.

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  • Null Value Statement

    - by Sam
    Hi All, I have created a table called table1 and it has 4 columns named Name,ID,Description and Date. I have created them like Name varchar(50) null, ID int null,Description varchar(50) null, Date datetime null I have inserted a record into the table1 having ID and Description values. So Now my table1 looks like this: Name ID Description Date Null 1 First Null One of them asked me to modify the table such a way that The columns Name and Date should have Null values instead of Text Null. I don't know what is the difference between those I mean can anyone explain me the difference between these select statements: SELECT * FROM TABLE1 WHERE NAME IS NULL SELECT * FROM TABLE1 WHERE NAME = 'NULL' SELECT * FROM TABLE1 WHERE NAME = ' ' Can anyone explain me?

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  • Confusion using MYSQLI

    - by user1020069
    I just started using mysqli API for PHP. Apparently, every time an object of the class MYSQLI is instantiated, it can setup a connection to the database as it connects to the server unlike mysql_connect, which connects to the server first and then you are required to specify the database to query. Now this is a good problem if the db exists, in my case, the db does not exist on the first ever connection to the server/execution of the problem, hence I must connect without specifying the database, which is fine, since the msyqli constructor does not make this database mandatory. My challenge is essentially, how do I check if the database exists before attempting the first connection. The only way to really do this would be to establish a conection to the server and then use the result of the following query to gauge if the database exists: SELECT COUNT(*) AS `exists` FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMATA.SCHEMA_NAME="dbname" ; If this returns true, then the database exists, but now the challenge is how do I get the mysqli object to query this database rather than having to prefix the name of the database in the query. Thanks much

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  • How to use SQLiteOpenHelper without or less restrictive use of Context?

    - by Pentium10
    If you extend SQLiteOpenHelper, for the Constructor you have to use a Context. I am wondering if there is a way to leave this out, and be able to work with database tables without a Context. Or at least be least restrictive, I mean a way of project/class structure that will make history the several context passings I have to do now. As it is my application has several level of classes, chained in each other, and there are a few that connects to the database, but have no whatsoever influence on the interface, so they don't actually need the Context. Are you creating your classes in the way that you pass each time a Context to them? If not, how you do, how you reuse a Context in a short class?

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  • Java: Friendlier way to get an instance of FontMetrics

    - by Martijn Courteaux
    Hi people, Is there a friendlier way to get an instance of FontMetrics than FontMetrics fm = Graphics.getFontMetrics(Font); I hate this way because of the following example: If you want to create in a game a menu and you want all the menuitems in the center of the screen you need fontmetrics. But, mostly, menuitems are clickable. So I create an array of Rectangles and all the rectangles fits around the items, so when the mouse is pressed, I can simply use for (int i = 0; i < rects.length; i++) if (rects[i].contains(mouseX, mouseY)) { ... } But to create the rects I also need FontMetrics for their coordinates. So this mean that I have to construct all my rectangles in the paint-method of my menu. So I want a way to get the FontMetrics so I can construct the Rectangles in a method called by the constructor. Hope you understand. Thanks in advance.

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  • Neo4j+Gremlin : Trouble with T.gte and floating point node attributes

    - by letronje
    For a type of nodes in my graph, attribute values for an attribute(named 'some_count') is either missing or an integer or a float. I'm trying to write gremlin to filter these nodes based on minimum value for this attribute. I first verified that the values are indeed present by firing the following gremlin g.v(XXX)._().in('category').hasNot('some_count', T.eq, null).back(1).some_count Next, I tried filtering by exact value and that works and show me the matching nodes or gives an empty array if there is no match g.v(XXX)._().in('category').hasNot('some_count', T.eq, null).back(1).has('some_count', T.eq, 120000.0d) But the following query that uses the 'greater than or equal to' comparator doesn't work. g.v(XXX)._().in('category').hasNot('some_count', T.eq, null).back(1).has('some_count', T.gte, 1.0d) this returns nil (I'm querying via ruby/rails using Neo4j AR Adapter ) Instead of returning an empty array for no match, it returns a nil, which tells me something could be wrong with the query itself. I'm running neo4j community server 1.8. Is there a way I can ask Neo4j to log errors/queries, to see what could be going wrong ?

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  • Bring Control to ToolBox

    - by Mohanavel
    I created a TextBoxControl which is inherited from Infragistics.Win.UltraWinEditors.UltraTextEditor, an Infragistics control. As showed below. public class TextBoxControl : Infragistics.Win.UltraWinEditors.UltraTextEditor { //My Stuff } At some level Infragistics.Win.UltraWinEditors.UltraTextEditor class also inherited from WinForm's "Control" class. My problem is, this control is not appearing in the ToolBox. I done two steps 1. Choose from browse option and select the dll where the class present 2. Drag and drop the dll directly to the ToolBox In-fact both are same, TextBoxControl control is not appearing in the ToolBox, what i missing here. Edit : TextBoxControl class have empty constructor, nothing special in this class.

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  • use of views for validation of an incorrect login-id or an unidentified user

    - by sqlchild
    I read this on msdn: Views let different users to see data in different ways, even when they are using the same data at the same time. This is especially useful when users who have many different interests and skill levels share the same database. For example, a view can be created that retrieves only the data for the customers with whom an account manager deals. The view can determine which data to retrieve based on the login ID of the account manager who uses the view. My question: For the above example , i would have to have a column named Userid/LoginId on my table on which the view is created so that i can apply a check option in the view for this column. and then if a user with a name not in that column tries to enter data , then he/she is blocked.

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  • C++ Types Impossible to Name

    - by Kirakun
    While reading Wikipedia's page on decltype, I was curious about the statement, Its [decltype's] primary intended use is in generic programming, where it is often difficult, or even impossible, to name types that depend on template parameters. While I can understand the difficulty part of that statement, what is an example where there is a need to name a type that cannot be named under C++03? EDIT: My point is that since everything in C++ has a declaration of types. Why would there ever be a case where it is impossible to name a type? Furthermore, aren't trait classes designed to yield type informations? Could trait classes be an alternative to decltype?

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  • How to transfer SQLite db to web server on android phone (android)

    - by Aditya Mehta
    Hello, I have "BackUpContacts.db" database in SQLiteDatabase, it has a table named "ContactInfo" with column names ContactId, ContactName, MobilePhone1, MobilePhone2, OfficePhone1, OfficePhone2, OfficePhone3, HomePhone1, HomePhone2 and TokenId. What i want is to transfer all data of "ContactInfo" table to the mysql database system at some server (means server has also a table similar to "ContactInfo", where all data of "ContactInfo" will be copied). The last important thing which i want is that, whenever i want to get contacts(of a specified TokenId) i can backup all those from server to the mobile device in an xml file. in short, can here anyone help me how to transfer sqlite db to a web server?

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  • Zend autloading different namespaces from the same directory?

    - by Sled
    Hey guys, I have a models directory in my project, and I would like to save/files classes there with different namespaces. Example: models/User.php with classname Model_User models/Table_User.php with classname Model_Table_User For the first namespace I have this in bootstrap.php $resourceLoader->addResourceTypes(array( 'model' => array( 'namespace' => 'Model', 'path' => 'models' ) )); I can't figure out how to add the second namespace so it detects files starting with Table_ Any ideas? For now I've added a second directory named 'tables' but it's getting confusing because I have each model name twice (once in the models diretory and once in the tables directory)

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  • C++ allocate objects on heap of base class with protected constructors via inheritance

    - by KRao
    I have a class with protected constructor: class B { protected: B(){}; }; Now I derive from it and define two static functions and I manage to actually create objects of the class B, but not on the heap: class A : public B { public: static B createOnStack() {return B();} //static B* createOnHeap() {return new B;} //Compile time Error on VS2010 }; B b = A::createOnStack(); //This works on VS2010! The question is: 1) Is VS2010 wrong in allowing the first case? 2) Is it possible to create objects of B without modifying B in any way (no friendship and no extra functions). I am asking, because it is possible to make something similar when dealing with instances of B and its member functions, see: http://accu.org/index.php/journals/296 Thank you in advance for any suggestion! Kind regards

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  • Should the name of my classes begin with 'Q' in Qt?

    - by Venemo
    Hello Everyone, When I first started working with Qt, it was extremely annoying that every class has a name beginning with 'Q', but now I've got used to it. I'm using Qt Creator, and it highlights code quite well. However, it only highlights class names beginning with 'Q'. And it highlights everything beginning with 'Q' even if there is no such type. It doesn't highlight custom class names. That makes me wonder, should I also begin all my class names with 'Q'? Or at least the reusable ones? (I mean, those that I put in a class library, or reuse in another app.) I've seen several places where they named their classes this way. Is it a good thing? I found this page about Qt's naming conventions, but it doesn't deal with this question. Also, I don't understand why Qt doesn't use namespaces.

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  • Google App Engine datastore-primary key

    - by megala
    Hi, I've created a table in the Google App Engine Datastore. It contains the following FIELDS(GROUPNAME,GROUPID,GROUPDESC). How do I set GROUPID as the primary key? My code is as follows: @Entity @Table(name="group" , schema="PUBLIC") public class Creategroup { @Basic private String groupname; @Basic private String groupid; @Basic private String groupdesc; public void setGroupname(String groupname) { this.groupname = groupname; } public String getGroupname() { return groupname; } public void setGroupid(String groupid) { this.groupid = groupid; } public String getGroupid() { return groupid; } public void setGroupdesc(String groupdesc) { this.groupdesc = groupdesc; } public String getGroupdesc() { return groupdesc; } public Creategroup(String groupname, String groupid, String groupdesc ) { // TODO Auto-generated constructor stub this.groupname = groupname; this.groupid = groupid; this.groupdesc = groupdesc; } }

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  • sql server 2008 express. cannot create mdf databse.

    - by yair
    Hi, I'm working with visual studio 2008 express and sql 2008 express. I'm trying to create mdf database (Add new Item ...)and I recieve the following error message: "a network-related or instance-specific error occured while establishing a connection to SQL Server. The server was not found or was not accessible. Verfy that instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named pipes Provider:40 - could not open connection to SQL)" Why ? Is it possible to create mdf database with SQL 2008 Express ? If it is then what to do ?

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