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• SQLiteOpenHelper problem

  - by Harsha M V

  I have created SQLiteOpenHelper class to help me open write the database. but i am not able to invoke it from the main.java activity I have created an Class which extends the Database Helper which is stored at /Messaging/src/com/v3/messaging/DatabaseHelper.java Code: http://pastebin.com/Z5qp32xu now i have this class called Main.java which will be the first activity on the launch of the application. But how can i make the DatabaseHelper.java run just to create the database but still be at the Main.java file. The database should be created with the tables only when the db or the tables dont exist. Main.java code: http://pastebin.com/LVFVuhA0 Now when i run the program. the database is not being created :( I am trying to learn Android. So please excuse me if i forgot to tell something.

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• C++ enforce conditions on inherited classes

  - by user231536

  I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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• does anyone see any issues with this thread pattern?

  - by prmatta

  Here is a simple thread pattern that I use when writing a class that needs just one thread, and needs to a specific task. The usual requirements for such a class are that it should be startable, stopable and restartable. Does anyone see any issues with this pattern that I use? public class MyThread implements Runnable { private boolean _exit = false; private Thread _thread = null; public void start () { if (_thread == null) { _thread = new Thread(this, "MyThread"); _thread.start(); } } public void run () { while (_exit) { //do something } } public void stop () { _exit = true; if (_thread != null) { _thread.interrupt(); _thread = null; } } } I am looking for comments around if I am missing something, or if there is a better way to write this.

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• EF Stored Procedure Complex Type

  - by Web Dev

  I am using EF4. I am somewhat confused on on the Entity Framework Complex name. When I go to Functional Import of a Stored Procedure name and it ask me to type in the Complex name, is that supposed to be the name of of a class that can handle that output. For examle, say if my stored procedure returns FirstName, LastName. Is the Complex name supposed to be a class that can handle that output in this case PersonName? public class PersonName { public string FirstName {get; set;} public string LastName {get;set} }

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• Why can't I enforce derived classes to have parameterless constructors?

  - by FrisbeeBen

  I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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• ActiveRecord, has_many, polymorphic and STI

  - by leomayleomay

  I've came into a problem while working with AR and polymorphic, here's the description, class Base < ActiveRecord::Base; end class Subscription < Base set_table_name :subscriptions has_many :posts, :as => :subscriptable end class Post < ActiveRecord::Base belongs_to :subscriptable, :polymorphic => true end in the console, >> s = Subscription.create(:name => 'test') >> s.posts.create(:name => 'foo', :body => 'bar') and it created a Post like: #<Post id: 1, name: "foo", body: "bar", subscriptable_type: "Base", subscriptable_id: 1, created_at: "2010-05-10 12:30:10", updated_at: "2010-05-10 12:30:10"> the subscriptable_type is Base but Subscription, anybody can give me a hand on this?

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• [C++] Question on Virtual Methods

  - by bobber205

  IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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• Rails 3 Order By Count on has_many :through

  - by goo

  I have an application where I can list Items and add tags to each Item. The models Items and Tags are associated like this: class Item < ActiveRecord::Base has_many :taggings has_many :tags, :through => :taggings end class Tagging < ActiveRecord::Base belongs_to :item belongs_to :tag end class Tag < ActiveRecord::Base has_many :taggings has_many :items, :through => :taggings end So, this many-to-many relationship allows me to set n tags for each Item, and the same tag can be used several times. I'd like to list all tags ordered by the number of items associated with this tag. More used tags, shows first. Less used, last. How can I do that? Regards.

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• How to instantiate objects of classes that have dependencies injected?

  - by chester89

  Let's say I have some class with dependency injected: public class SomeBusinessCaller { ILogger logger; public SomeBusinessCaller(ILogger logger) { this.logger = logger; } } My question is, how do I instantiate an object of that class? Let's say I have an implementation for this, called AppLogger. After I say ObjectFactory.For<ILogger>().Use<AppLogger>(); how do I call constructor of SomeBusinessCaller? Am I calling SomeBusinessCaller caller = ObjectFactory.GetInstance<SomeBusinessCaller>(); or there is a different strategy for that?

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• Where Should Using Statements Be Located [closed]

  - by Bobby Ortiz - DotNetBob

  Possible Duplicate: What is the difference between these two declarations? I recently started working on a project with using statement located inside the NameSpace block. namespace MyApp.Web { using System; using System.Web.Security; using System.Web; public class MyClass { I usually put my using statements above the namespace block. using System; using System.Web.Security; using System.Web; namespace MyApp.Web { public class MyClass { I don't think it matters, but I am currious if someone else had a recommendation and could they explain why one way is better than another. Note: I always have one class per file.

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• Why is it possible to save entity but not delete if transactional annotation is set to readonly=true

  - by jakob

  Hello experts! My class is annotated with org.springframework.transaction.annotation.Transactional like this: @Transactional(readOnly = true) public class MyClass { I then have a dao class: @Override public void delete(final E entity) { getSession().delete(entity); } @Override public void save(final E entity) { getSession().saveOrUpdate(entity); } Then I have two methods in MyClass @Transactional(readOnly = false) public void doDelete(Entity entity){ daoImpl.delete(entity) } //@Transactional(readOnly = false) public void doSave(){ daoImpl.save(entity) } Saving and deleting works like a charm. But if I remove the @Transactional(readOnly = false) on doDelete method deletion stops working, Saving works with and without the method annotation. So my question is: WHY?

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• Force result for empty() test on an object

  - by hsz

  Hello ! Simple class for example: class Foo { protected $_bar; public function setBar( $value ) { $this->_bar = $value; } } And here is the question: $obj = new Foo(); var_dump( empty( $obj ) ); // true $obj->setBar( 'foobar' ); var_dump( empty( $obj ) ); // false Is it possible to change class's behaviour with testing it with empty() function so it will returns true when object is not filled with data ? I know about magic function __isset( $name ) but it is called only when we test specific field like: empty( $obj->someField ); but not when test whole object.

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• Cannot call struct properties from HAML file

  - by Lander

  I have the following code in my controller: @nav_items = ActiveSupport::OrderedHash.new @nav_items[:home] = Struct::NavItem.new("Home", nil, "/", "icon-home") @nav_items[:about] = Struct::NavItem.new("About", nil, "/about", "icon-heart") @nav_items[:contact] = Struct::NavItem.new("Contact", nil, "/contact", "icon-envelope") if (current_user != nil && current_user.admin?) @nav_items[:admin_divider] = Struct::NavItem.new(nil, "divider-vertical", nil, nil) @nav_items[:admin] = Struct::NavItem.new("Admin", nil, "/admin", "") end And the following in my view: - @nav_items.each do |nav_item| %li{ :class => nav_item[:class] } %a{ :href => nav_item[:link] }= nav_item[:text] And my struct definition: Struct.new("NavItem", :text, :class, :link, :icon_class) I'm relatively new to Ruby, Rails, and HAML, but in another project using ERB rendering, code like that worked fine. I've tried referencing properties by doing something like nav_item.link as well, but that still does not work. The error I get with my current code is: Symbol as array index By using code like nav_item.link: undefined method `link' for #< Array:0x126970ff0 As this is my first time using HAML, I'm not too sure what I'm doing wrong.

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• Can you have a web application project produce multiple DLLS?

  - by chris

  I have a VS 2008 web application project that is getting large. My structure looks like: - WebRoot - Common/ - Foo/ - Bar/ - Baz/ so I end up with a single Webroot.dll that contains the code for common, foo, bar, and baz. Is it possible to set it so that I end up with common/ in webroot.dll, and code in foo ends up in foo.dll, bar in bar.dll, etc? Update: A couple of suggestions to move some stuff into class libraries. We already have a dozen or so separate class library projects as part of the solution; Foo, Bar and Baz contain nothing but web forms and the associated code-behinds, so moving them into separate class library projects is not feasible.

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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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• 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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• Parsing data without HMLT tags

  - by user296507

  Hi, I need to extract the actual phone number form the html listed below, but I'm not really sure how to do it using Nokogiri CSS since there are no html tags around it. When an at_css(.phonetitle) it only parse Phone and not the number. <div class="detail"> <span class="address">Corner of Toorak Road and Chapel Street, South Yarra</span><br> <span class="phonetitle">Phone</span> 95435 34341 <br><br> </div>

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• Is it possible to select data with max value for a column using Criteria in Hibernate?

  - by Palo

  Lets say I have the following mapping: <hibernate-mapping package="mypackage"> <class name="User" table="user"> <id name="id" column="id"> <generator class="native"></generator> </id> <property name="name" /> <property name="age" /> </class> </hibernate-mapping> Is it possible to select the oldest user (that is age is maximal) using Criteria in Hibernate? I can imagine that i could do this with 2 selects. (first select total number of users and then order the entries descending by age and select the first entry). But is it possible with a single select? Thank you Palo

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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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• Methods specific only to an instance? What are they called in Ruby?

  - by daremarkovic

  I know there are "instance methods", "class methods" but what are these types of methods called, for eg: s1 = "This is my STRING!" def s1.m1 downcase end p s1 # => "This is my STRING!" p s1.m1 # => "this is my string!" What type of method is the "m1" method called on the s1 "instance" of the "string" class? It's really weird because I didn't know this was possible at all if I try: s2 = "This is ANOTHER string" s2.m1 # => Won't work! Which kind of makes sense, but not sure why defining methods like m1 on instances on a class are useful at all.

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• WPF data binding issue .

  - by Praveen

  Hi All, I have a wpf app and there i simply have a dock panel and inside dock panel i have a textblock. I want to bind the text property of textblock to my custom objects property but that' not working. I think i am missing something here but don't know what. Here is the code snippet. <TextBlock Text="{Binding Source=myDataSource, Path=ColorName}"/> </DockPanel> My custom class. class MyData { public string ColorName { get; set; } } and main window constructor.. public partial class MainWindow : Window { MyData myDataSource; public MainWindow() { InitializeComponent(); myDataSource = new MyData { ColorName = "Red" }; } }

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• Problems with ActiveRecord assoc

  - by ciss

  Hello again, so i write my e-commerce shop cms and have some strange error: ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'id' in 'where clause': DELETE FROM `properties` WHERE `id` = NULL so, i have three models Items: class Item < ActiveRecord::Base has_many :properties, :dependent => :destroy has_many :types, :through => :property end Type: class Type < ActiveRecord::Base has_many :properties, :dependent => :destroy end Properties: class Property < ActiveRecord::Base belongs_to :item belongs_to :type end So, all is okay, but when i try to item.destroy() i have error =( This is my test code: test "should destroy associated properties" do item = Item.create(:name => "Jeans") type = Type.create(:key => "color") property = Property.new property.item = item property.type = type property.save item.destroy() end

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• template specilization using member enums

  - by Altan

  struct Bar { enum { Special = 4 }; }; template<class T, int K> struct Foo {}; template<class T> struct Foo<T::Special> {}; Usage: Foo<Bar> aa; fails to compile using gcc 4.1.2 It complains about the usage of T::Special for partial specilization of Foo. If Special was a class the solution would be to a typename in front of it. Is there something equivalent to it for enums (or integers)? Thanks, Altan

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• What is the definition of a Service object ?

  - by Maskime

  I've been working a lot with PHP. But recently i was sent on a work wich use Java. In PHP i used to do a lot of Singleton object but this pattern has not the same signification in Java that it has in PHP. So i wanted to go for an utility class (a class with static method) but my chief doesn't like this kind of classes and ask me to go for services object. So my guess was that a service object is just a class with a constructor that implement some public methods... Am i right ?

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• Mapping to a different view based on child type

  - by Ryan Burnham

  So i have a situation where i have common base type but i need to map to a different view based on the child type. It looks like i can use a generic mapping class to handle the inheritance http://geekswithblogs.net/nharrison/archive/2010/07/09/inheriting-a-class-map-in-fluent-nhibernate.aspx But how can i conditionally map to a different view based on the child type? I see an EntityType property but it says its obsolete and will be made private in the next version. As an example i have a base class of ContactInfo is standard between contact types but the values come from different places depending on the contact type, this I'll handle through the sql view.

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