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• When is it appropriate to use C++ exceptions?

  - by krebstar

  I'm trying to design a class that needs to dynamically allocate some memory.. I had planned to allocate the memory it needs during construction, but how do I handle failed memory allocations? Should I throw an exception? I read somewhere that exceptions should only be used for "exceptional" cases, and running out of memory doesn't seem like an exceptional case to me.. Should I allocate memory in a separate initialization routine instead and check for failures and then destroy the class instance gracefully? Or should I use exceptions instead? The class won't have anything useful to do if these memory allocations should fail.. EDIT: The consensus seems to be that running out of memory IS an exceptional case. Will see how to go about this.. Thanks.. :)

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• How to specify a different column for a @Inheritance JPA annotation

  - by Cue

  @Entity @Inheritance(strategy = InheritanceType.JOINED) public class Foo @Entity @Inheritance(strategy = InheritanceType.JOINED) public class BarFoo extends Foo mysql> desc foo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ mysql> desc barfoo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | | foo_id | int | | bar_id | int | +---------------+-------------+ mysql> desc bar; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ Is it possible to specify column barfo.foo_id as the joined column? Are you allowed to specify barfoo.id as BarFoo's @Id since you are overriding the getter/seeter of class Foo? I understand the schematics behind this relationship (or at least I think I do) and I'm ok with them. The reason I want an explicit id field for BarFoo is exactly because I want to avoid using a joined key (foo _id, bar _id) when querying for BarFoo(s) or when used in a "stronger" constraint. (as Ruben put it)

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• How to build the ViewModel in MVVM not to violate the Single Responsibility Principle?

  - by Przemek

  Robert Martin says: "There should never be more than one reason for a class to change". Let's consider the ViewModel class which is bound to a View. It is possible (or even probable) that the ViewModel consists of properties that are not really related to each other. For small views the ViewModel may be quite coherent, but while the application gets more complex the ViewModel will expose data that will be subject to change for different and unrelated reasons. Should we worry about the SRP principle in the case of ViewModel class or not?

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• patching java reflect calls using AOP

  - by Oleg Pavliv

  I don't have a lot of experience with Jboss AOP and I'm just curious if it's possible to replace all calls like Field f = foo.class.getDeclaredField("bar"); f.set(object, value); with something like Field f = foo.class.getDeclaredField("bar"); FieldSetCaller.invoke(f, object, value); using Jboss AOP. FieldSetCaller is my own class. I need to replace all Field.set calls on the fly, without recompiling the code. Some third -party code I even cannot recompile because I don't have the source. I can achieve this using java asm framework and I'm wandering if Jboss AOP can do it as well. Just for information - my code is running on Jboss server 4.3.0

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• How to put tags inside an html attribute?

  - by Mycol

  Using xslt i want to create an attribute: <span class="tooltip"> <xsl:attribute name="onmouseover"> <xsl:text>javascript:function(</xsl:text> <span class="label">Aggiunta</span> <xsl:apply-tempaltes/> <xsl:text>)</xsl:text> </xsl:attribute> The problem is that only the pure text is putted inside the attribute, like <span class="tooltip" onmouseover="javascript:function(Aggiunta ...)"> whithout the span tags or the tags that may come from apply-templates. So how can I put html code into an attribute?

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• Accessing typedef from the instance

  - by piotr

  As in stl containers, why can't we access a typedef inside the class from the class instance? Is there a particular insight into this? When value_type was a template parameter it could help making more general code if there wasn't the need to specify the template parameters as in vector::value_type Example: class T { public: typedef int value_type; value_type i; }; T t; T::value_type i; // ok t.value_type i; // won't work

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• Building a wiki like data model in rails question.

  - by lillq

  I have a data model in which I would like to have an item that has a description that can be edited. I would like to also keep track of all edits to the item. I am running into issues with my current strategy, which is: class Item < ActiveRecord::Base has_one :current_edit, :class_name => "Edit", :foreign_key => "current_edit_id" has_many :edits end class Edit < ActiveRecord::Base belongs_to :item end Can the Item have multiple associations to the same class like this? I was thinking that I should switch to keeping track of the edit version in the Edit object and then just sorting the has_many relationship base on this version.

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• Is it possible to group validation?

  - by lambdabutz

  I am using a lot of my own validation methods to compare the data from one association to the other. I've noticed that I'm constantly checking that my associations aren't nil before trying to call anything on them, but I am also validating their presence, and so I feel that my nil checks are redundant. Here's an example: class House < ActiveRecord::Base has_one :enterance, :class => Door has_one :exit, :class => Door validates_presence_of :enterance, :exit validate :not_a_fire_hazard def not_a_fire_hazard if enterance && exit && enterance.location != exit.location errors.add_to_base('If there is a fire you will most likely die') return false end end end I feel like I am repeating myself by checking the existence of enterance and exit within my own validation. Is there a more "The Rails Way" to do this?

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• Overriding fetch in multiple spine models

  - by Adam Charnock

  I need to override Spine's @fetch() method in all of my Spine models. Currently I have code duplication as follows: TastypieEndpointMixin = fromJSON: (data) -> return unless data return Spine.Model.fromJSON(data.objects) class App.models.Position extends Spine.Model @configure 'Position', 'code', 'name' @extend Spine.Model.Ajax @extend TastypieEndpointMixin @url: '/api/v1/position/?format=json' validate: -> 'code is required' unless @code @fetch: -> defer = $.Deferred() @one "refresh", -> defer.resolve() super return defer class App.models.Player extends Spine.Model @configure 'Player', 'first_name', 'last_name', ... @extend Spine.Model.Ajax @extend TastypieEndpointMixin @url: '/api/v1/player/?format=json' @fetch: -> defer = $.Deferred() @one "refresh", -> defer.resolve() super return defer My question is: How can I create some form of parent class which contains @fetch()? I know this should be a simple problem to solve. I have tried many options (including extending Spine.Model and Spine.Model.Ajax), but nothing works and I cannot seem to get my head around it.

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• Importing Classes Within a Module

  - by CodeJoust

  Currently, I have a parser with multiple classes that work together. For Instance: TreeParser creates multiple Product and Reactant modules which in turn create multiple Element classes. The TreeParser is called by a render method within the same module, which is called from the importer. Currently, using the class name in the imported module file works only if the file calling the module contains from module_name import *, so the classes are imported into the main namespace. Finally, if the package has dependencies (such as re and another another module within the same folder), where is the best place to require those modules? Within the __init__.py file or within the module itself? I don't really want to add the module name in front of every call to the class, in case I do call import *, however, is it possible to use a variable name of the current module to call the class, or use a workaround in the __init__.py file? I'm probably used to the ruby require '' method instead of python's module system.

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• Is there performance to be gained by moving storage allocation local to a member function to its cla

  - by neuviemeporte

  Suppose I have the following C++ class: class Foo { double bar(double sth); }; double Foo::bar(double sth) { double a,b,c,d,e,f a = b = c = d = e = f = 0; /* do stuff with a..f and sth */ } The function bar() will be called millions of times in a loop. Obviously, each time it's called, the variables a..f have to be allocated. Will I gain any performance by making the variables a..f members of the Foo class and just initializing them at the function's point of entry? On the other hand, the values of a..f will be dereferenced through this-, so I'm wondering if it isn't actually a possible performance degradation. Is there any overhead to accessing a value through a pointer? Thanks!

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• How to tell a method has a varargs argument using reflection?

  - by Anthony Kong

  Here is a sample code package org.example; import java.lang.reflect.Method; class TestRef { public void testA(String ... a) { for (String i : a) { System.out.println(i); } } public static void main(String[] args){ Class testRefClass = TestRef.class; for (Method m: testRefClass.getMethods()) { if (m.getName() == "testA") { System.out.println(m); } } } } The output is public void org.example.TestRef.testA(java.lang.String[]) So the signature of the method is reported to take a array of String. Is there any mean in the reflection library I can tell that the method is originally declared to take a varargs?

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• How do you set up your JScript (NOT JScript.NET) development environment?

  - by jJack

  In my environment, if I create a class in JScript syntax: class test{ } and then save it to a file named "test.js" and run it with wscript, I get a Microsoft JScript "Syntax error" at line 1. However, if I simply, say, write a function: function getInput() { var wshell = WScript.CreateObject("WScript.Shell"); wshell.Popup ("Do you want to continue?"); return userInput } getInput() and run it the same way, it works. Hopefully, there is something fundamentally wrong with my class definition. If that is the case, I am excited to find out.

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• Excluding some classes from the cobertura report doesn't work

  - by user357480

  I tried to exclude some classes from cobertura as specified in this site <cobertura-instrument todir="${voldemort.instrumented.dir}" datafile="${cobertura.instrument.file}"> <classpath refid="tools-classpath" /> <ignore regex=".*\.xsd" /> <fileset dir="${voldemort.dist.dir}/classes"> <include name="**/*.class" /> <exclude name="**/client/protocol/pb/*.class"/> <exclude name="**/server/http/*.class"/> </fileset> </cobertura-instrument> but that doesn't work help me out, pleaseeeeeeeeeeee

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• jQuery selector question

  - by Jakey

  I have a span and an anchor inside a table cell. I have the anchor set up to show a tooltip. I would like the text inside the span to be used for the tooltip. How can I select this text in jQuery? <td class="row-head" colspan="5"><span class="tip-text">Complete Coverage</span><a href="#" class="help"></a></td> JQuery code - the current selector always finds the first instance only for all tips. $(document).ready(function() { $('.help').qtip({ style: { name: 'cream', tip: true }, content: { text: $(this).find('span.tip-text').html() } }); }); Thanks

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• ASP.NET Thread Safety in aspx.cs code behind file

  - by Tim Michalski

  I am thinking of adding a DataContext as a member variable to my aspx.cs code-behind class for executing LinqToSql queries. Is this thread safe? I am not sure if a new instance of this code-behind class is created for each HTTP request, or if the instance is shared amongst all request threads? My fear is that I will get 10 simultaneous concurrent http requests that will be using the same database session. public partial class MyPage : System.Web.UI.Page { private DataContext myDB = new DataContext(); protected void MyAction_Click(object sender, EventArgs e) { myDB.DoWork(); } }

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• Is this crufty?

  - by bobobobo

  I'm writing code like: class Game { int getMouseX() { return inputManager.getMouseX() ; } } ; I remember seeing code like this and hating it. One function passes off to another? What is this "pattern" (or, possibly, anti-pattern) called? I don't like it! On the other hand, it saves exposing the InputManager to the user of the class... would that be a better choice? Or should Game simply not contain InputManager? Edit What about using multiple inheritance instead? class Game : public InputManager, public Window { // by virtue of inheriting InputManager and Window, // Game now has "acquired" the capabilities of // InputManager's public functions, without requiring delegate. } ; Have I not found a reasonably good use for multiple inheritance??

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• how to open many files simultaneously for reading in c

  - by monkeyking

  I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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• Is it good practice to put private API in the .m files and public API in .h files in Cocoa?

  - by Paperflyer

  Many of my classes in my current project have several properties and methods that are only ever called from within the class itself. Also, they might mess with the working of the class depending on the current state of the class. Currently, all these interfaces are defined in the main interface declaration in the .h files. Is it considered good practice to put the “private” methods and properties at the top of the .m files? This won't ever affect anything since I am very likely the only person ever to look at this source code, but of course it would be interesting to know for future projects.

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• IntelliJ: Including jars in a jar artifact

  - by skiaddict1

  Developing on the Mac with IntelliJ 9.0.2. I have a program which depends on two library jars. I have figured out how to get IntelliJ to make me a jar of my source (with the Artifact tab), and even to include the two jars in it. However, if I get a listing of the jar file it produces, it looks like this: com/acme/MyClass1.class com/acme/MyClass2.class ... mylib1.jar myLib2.jar And, no surprises, if I double-click the jar file, it gets a NoClassDefFoundError the first time it tries to access a class in one or other library jar. How do I get IntelliJ to include the two library jars such that the classes are visible?

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• what is the best way to have a Generic Comparer

  - by oo

  I have a lot of comparer classes where the class being compared is simply checking the name property of the object and doing a string compare. For example: public class ExerciseSorter : IComparer<Exercise> { public int Compare(Exercise x, Exercise y) { return String.Compare(x.Name, y.Name); } } public class CarSorter : IComparer<Car> { public int Compare(Car x, Car y) { return String.Compare(x.Name, y.Name); } } what is the best way to have this code generic so i dont need to write redundant code over and over again.

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

  - 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 updated2 and the classmethods: class a: @classmethods def b(x): print 'sss' aa=a() print aa.b the Traceback is : Traceback (most recent call last): File "D:\zjm_code\a.py", line 5, in <module> class a: File "D:\zjm_code\a.py", line 6, in a @classmethods NameError: name 'classmethods' is not defined

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• Why are static imports of static methods with same names legal?

  - by user1055638

  Lets say we have these packages and classes: package p1; public class A1 { public static void a() {} } package p2; public class A1 { public static void a() {} } package p3; import static p1.A1.a; import static p2.A1.a; public class A1 { public static void test() { } } I am wondering, why the static import of methods is legal (won't result in compile time error) in package p3? We won't be able to use them further in the test() method as such usage will result in the compile time error. Why it is not the same as with a normal import of classes. Lets say we would like to import classes A1 from packages p1 and p2 into p3: package p3; import p1.A1; import p2.A1; such import is illegal and will result in the compile time error.

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• Explanation of output

  - by Anon

  My program class Building { Building() { System.out.print("b "); } Building(String name) { this(); System.out.print("bn " + name); } }; public class House extends Building { House() { System.out.print("h "); // this is line# 1 } House(String name) { this(); // This is line#2 System.out.print("hn " + name); } public static void main(String[] args) { new House("x "); } } We know that compiler will write a call to super() as the first line in the child class's constructor. Therefore should not the output be: b (call from compiler written call to super(), before line#2 b (again from compiler written call to super(),before line#1 ) h hn x But the output is b h hn x Why is that?

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• Rails ActiveRecord- has_many through and belongs_to a related model

  - by Nick

  I have 3 models sites, user_favorites and users. Relevant relationships: class Site < ActiveRecord::Base has_many :users, :through => :user_favorites class UserFavorite < ActiveRecord::Base belongs_to :user, :counter_cache => true belongs_to :site end class User < ActiveRecord:Base has_many :user_favorites has_many :sites, :through => :user_favorites All of that works just fine. I'd like to add a new attribute to the Site model to indicate which user created it. I don't believe this constitutes a has_and_belongs_to_many scenario. A site has many users through user_favorites but I want it to belong to a single user reflecting the owner/creator. I'm wondering what the ORM best practice is for this. SQL wise I'd just use different joins depending on what I was trying to query with a created_by FK in Site. Sorry if I'm missing something basic here. Thanks

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