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• When exactly does a method have side effects?

  - by Kim

  As I always understood it, any change to the programs state (or anything to do with IO) is a side effect. It does not matter, whether the change occurs in a global variable or in a private field of the object the method is called on. It follows that all methods which do not return anything either do nothing at all or have a side effect. My confusion comes from one of our university's instructors (who is still a student and thus not omniscient yet;) ) telling me setters don't have side effects.

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• StringBuilder/StringBuffer vs. "+" Operator

  - by matt.seil

  I'm reading "Better, Faster, Lighter Java" (by Bruce Tate and Justin Gehtland) and am familiar with the readability requirements in agile type teams, such as what Robert Martin discusses in his clean coding books. On the team I'm on now, I've been told explicitly not to use the "+" operator because it creates extra (and unnecessary) string objects during runtime. But this article: http://www.ibm.com/developerworks/java/library/j-jtp01274.html Written back in '04 talks about how object allocation is about 10 machine instructions. (essentially free) It also talks about how the GC also helps to reduce costs in this environment. What is the actual performance tradeoffs between using "+," "StringBuilder," or "StringBuffer?" (In my case it is StringBuffer only as we are limited to Java 1.4.2.) StringBuffer to me results in ugly, less readable code, as a couple of examples in Tate's book demonstrates. And StringBuffer is thread-synchronized which seems to have its own costs that outweigh the "danger" in using the "+" operator. Thoughts/Opinions?

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• Hibernate criteria with projection not performing query for @OneToMany mapping

  - by Josh

  I have a domain object, Expense, that has a field called initialFields. It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection that is behaving this way. If I use a regular HQL query initialFields is populated appropriately, but of course I can't limit the fields. Anyone ever seen anything like this?

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• Compiled query using list of class objects in C#

  - by Sukan

  Hello , Can somebody help me out in creating compiled queries where input is to be a list of class objects? I have seen examples where Func<DataContext, somematchobject, IQueryable<T>> is created and compiled. But can I do something like Func<List<T>, matchObject, T>, and compile it? Basically I want an object(T) meeting certain conditions (as in matchObject) to be returned from a list of objects(List<T>). Will CompiledQuery.Compile help me in this? Please help me experts!!

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• Disallow private constructor invocation in friend function

  - by user2907032

  Is there any way to not allow private construction in friend function, In case we do have private constructor with friend function in our class. Only Static method should be responsible for object creation and other than this compiler should flash error message #include <iostream> #include <memory> using namespace std; class a { public: void see () { cout<<"Motimaa"; } static a& getinstance() { static a instance; return instance; } private: a() {}; friend void access(); }; void access () { a obj; obj.see();//still friend function can access } int main() { a::getinstance().see(); access(); return 1; }

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• Using textbox text in javascript

  - by Jambo

  I am working with Twitter widgets with the following script- <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> <input type="button" value="Run Function" onclick="test();" /> <script> function test() { new TWTR.Widget({ version: 3, type: 'profile', rpp: 8, interval: 30000, width: 315, height: 340, theme: { shell: { background: '#333333', color: '#ffffff' }, tweets: { background: '#000000', color: '#ffffff', links: '#4aed05' } }, features: { scrollbar: false, loop: false, live: false, behavior: 'all' } }).render().setUser(document.getElementById('TextBox1').value).start(); } When using the function test(); in the button click it is ocming up with the error - Error: Unable to get value of the property 'value': object is null or undefined So it seems like it is not getting to the value at - (document.getElementById('TextBox1').value) I am not sure why it is null if the text box has a value and then the script is run on the button click?

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• what is this 'content_type' mean..

  - by zjm1126

  content_type = ContentType.objects.get_for_model(Map) maps = maps.extra(select=SortedDict([ ('member_count', MEMBER_COUNT_SQL), ('topic_count', TOPIC_COUNT_SQL), ]), select_params=(content_type.id,)) and the ContentType is: class ContentType(models.Model): name = models.CharField(max_length=100) app_label = models.CharField(max_length=100) model = models.CharField(_('python model class name'), max_length=100) objects = ContentTypeManager() class Meta: verbose_name = _('content type') verbose_name_plural = _('content types') db_table = 'django_content_type' ordering = ('name',) unique_together = (('app_label', 'model'),) def __unicode__(self): return self.name def model_class(self): "Returns the Python model class for this type of content." from django.db import models return models.get_model(self.app_label, self.model) def get_object_for_this_type(self, **kwargs): """ Returns an object of this type for the keyword arguments given. Basically, this is a proxy around this object_type's get_object() model method. The ObjectNotExist exception, if thrown, will not be caught, so code that calls this method should catch it. """ return self.model_class()._default_manager.using(self._state.db).get(**kwargs) def natural_key(self): return (self.app_label, self.model) i want to know: what is the 'content_type' used for ??

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• How can I use the FOR attribute of a LABEL tag without the ID attribute on the INPUT tag

  - by Shawn

  Is there a solution to the problem illustrated in the code below? Start by opening the code in a browser to get straight to the point and not have to look through all that code before knowing what you're looking for. <html> <head> <title>Input ID creates problems</title> <style type="text/css"> #prologue, #summary { margin: 5em; } </style> </head> <body> <h1>Input ID creates a bug</h1> <p id="prologue"> In this example, I make a list of checkboxes representing things which could appear in a book. If you want some in your book, you check them: </p> <form> <ul> <li> <input type="checkbox" id="prologue" /> <label for="prologue">prologue</label> </li> <li> <input type="checkbox" id="chapter" /> <label for="chapter">chapter</label> </li> <li> <input type="checkbox" id="summary" /> <label for="summary">summary</label> </li> <li> <input type="checkbox" id="etc" /> <label for="etc">etc</label> <label> </li> </ul> </form> <p id="summary"> For each checkbox, I want to assign an ID so that clicking a label checks the corresponding checkbox. The problems occur when other elements in the page already use those IDs. In this case, a CSS declaration was made to add margins to the two paragraphs which IDs are "prologue" and "summary", but because of the IDs given to the checkboxes, the checkboxes named "prologue" and "summary" are also affected by this declaration. The following links simply call a javascript function which writes out the element whose id is <a href="javascript:alert(document.getElementById('prologue'));">prologue</a> and <a href="javascript:alert(document.getElementById('summary'));">summary</a>, respectively. In the first case (prologue), the script writes out [object HTMLParagraphElement], because the first element found with id "prologue" is a paragraph. But in the second case (summary), the script writes out [object HTMLInputElement] because the first element found with id "summary" is an input. In the case of another script, the consequences of this mix up could have been much more dramatic. Now try clicking on the label prologue in the list above. It does not check the checkbox as clicking on any other label. This is because it finds the paragraph whose ID is also "prologue" and tries to check that instead. By the way, if there were another checkbox whose id was "prologue", then clicking on the label would check the one which appears first in the code. </p> <p> An easy fix for this would be to chose other IDs for the checkboxes, but this doesn't apply if these IDs are given dynamically, by a php script for example. Another easy fix for this would be to write labels like this: <pre> &lt;label&gt;&lt;input type="checkbox" /&gt;prologue&lt;/label&gt; </pre> and not need to give an ID to the checkboxes. But this only works if the label and checkbox are next to each other. </p> <p> Well, that's the problem. I guess the ideal solution would be to link a label to a checkboxe using another mechanism (not using ID). I think the perfect way to do this would be to match a label to the input element whose NAME (not ID) is the same as the label's FOR attribute. What do you think? </p> </body> </html>

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• Calling a method with getattr in Python

  - by brain_damage

  How to call a method using getattr? I want to create a metaclass, which can call non-existing methods of some other class that start with the word 'oposite_'. The method should have the same number of arguments, but to return the opposite result. def oposite(func): return lambda s, *args, **kw: not oposite(s, *args, **kw) class Negate(type): def __getattr__(self, name): if name.startswith('oposite_'): return oposite(self.__getattr__(name[8:])) def __init__(self,*args,**kwargs): self.__getattr__ = Negate.__getattr__ class P(metaclass=Negate): def yep(self): return True But the problem is that self.__getattr__(sth) returns a NoneType object. >>> p = P() >>> p.oposite_yep() Traceback (most recent call last): File "<pyshell#115>", line 1, in <module> p.oposite_yep() TypeError: <lambda>() takes at least 1 positional argument (0 given) How to deal with this?

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• How to share a variable between two classes?

  - by Altefquatre

  How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it?

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• REST API for driving distance?

  - by Mark

  Is there a service that will give me the driving distance between two addresses? Apparently Google Maps API requires you to display a map, which I don't want to do (on that particular page), and I'd like to just snag the data and save it to my DB after a user submits a form, rather than waiting for JS to do it's thing. If it's relevant, this is going into a Django app. I discovered that CloudMade offers a Python API, which is nice, except their latest dev release has a bug in it (can't use the API object), but more importantly, it's support for Canada is awful/worthless (couldn't find directions from any major city around here!).

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• 'Out of Memory exception' in sql server 2005 xml column

  - by Raghuraman

  Hi All, I am devloping a windows forms application and am using sql server 2005 database as my backend. I am having an xml column in my database. I am using ultrawingrid control in my application.I obtain the xml of the dataset which is bound to my ultrawingrid control and pass that as a parameter value to the stored procedure where am inserting this value into the xml column which I specified. The columns in my grid are dynamic and hence there can be any no of columns in my grid. I got 'out of memory' exception in the dataset.GetXml() statement since there were more no of columns I believe.So, what I did is that I used dataset.WriteXml() method and stored all the xml contents into an xml file, loaded the xml file into the XmlDocument object and then passed the xmlnodereader as the value to the stored procedure parameter.Now, while executing the stored procedure am getting the same 'out of memory' exception. How could I resolve this issue?

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• .Net Thread Synchronization

  - by user209293

  Hello, I am planning to use Auto reset Event Handle for Inter Thread communication. EventWaitHandle handle = new EventWaitHandle(false, EventResetMode.AutoReset); My producer thread code look like below produceSomething(); handle.Set(); In the consumer thread, I have to download data for every one minute or when prodcuer is called Set method try { while(true) { handle.WaitOne(60000, false); doSomething(); - downloads data from internet. takes lot of time to complete it. } } catch(ThreadAbortException) { cleanup(); } My question is if consumer thread is running doSomething funtion and producer calls set function, what would be state of Auto reset event object? My requreiment is as soon as producer calls set method i have to downlaod fresh data from intenet . If doSomething function is running, when Producer calls set method, i have to interrupt it and call again. Any help is appreciated. Regards Raju

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• How Do I See The Final Text Of A Query Resulting From A Call To mysqli->prepare?

  - by Joshua

  After code like this: $stmt = $mysqli->prepare("SELECT District FROM City WHERE Name=?")) { $stmt->bind_param("s", $city); $stmt->execute(); $stmt->bind_result($district); $stmt->fetch(); printf("%s is in district %s\n", $city, $district); How Do I See The Actual SQL Statement That Was Executed? (It Should Look Something Like "SELECT District FROM City WHERE Name='Simi Valley';") I already realize that in this simplistic case it would be very easy to simply reconstruct the query... but how can I access it in a general way that will work for very complicated prepared statements, and cases where I don't necessarily already understand the intended structure of the query, etc. Isn't there some function or method that can be called on the statement object that will return the actual text of the SQL query, after binding?

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• Create generic class instance throws TypeLoadException

  - by Elisa

  My TestLayer class has the namespace: "BLL.Infrastructure.TestLayer" and is inside the assembly: "BLL" public class LayerFactory<T, U> { public static IBaseLayer<T, U> Get() { var obj = Activator.CreateInstance("BLL", "BLL.Infrastructure.TestLayer", new object[] { (IBaseLayer<T, U>)null }); } } When I run the code the Activator throws an TypeLoadException with no more details Thats the concrete class it should create: GenericBaseLayer implements the IBaseLayer. public class TestLayer<T, U> : GenericBaseLayer<MyRequest, MyInfo.ActionType> { public TestLayer(IBaseLayer<MyRequest, MyInfo.ActionType> layer) : base(layer) { } } What do I wrong?

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• SQL Server 2005 drop column with constraints

  - by Julien N

  Hi ! In Sql Server 2005 I have a column with a "DEFAULT" constraint. I'd like to create a script that drops that column. The problem is that is returns me that error : Msg 5074, Level 16, State 1, Line 1 The object 'DF__PeriodSce__IsClo__4BCC3ABA' is dependent on column 'IsClosed'. Msg 4922, Level 16, State 9, Line 1 ALTER TABLE DROP COLUMN IsClosed failed because one or more objects access this column. I couldn't find an easy way to drop a column and all its associated constraints (only found big scripts that look into system table... there MUST (!!) be a "nice" way to do that !). And as the DEFAULT constraint's name has been randomly generated, I can't drop it by name. Thanks for your help.

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• How to use error provider at run time along with associating any control to validate

  - by Shantanu Gupta

  I am trying to create a Validation in a reusable fashion. Purpose: Make the validation control reusable. Error Provider should associate with control passed dynamically and can be set or cleared at run time. When user press OnClick event then all the controls gets validated with their own Error Providers. public bool IsFieldEmpty(ref TextBox txtControl, Boolean SetErrorProvider,string msgToShowOnError) { ErrorProvider EP = new ErrorProvider(); if (txtControl.Text == string.Empty) { if(SetErrorProvider==true) EP.SetError(txtControl, msgToShowOnError); return true; } else { if(SetErrorProvider==true) EP.Clear(); return false; } } Issue: Every time the function is called new errorprovider object gets created which i dont want. Every control should not have more than 1 error provider and i should be able to search it just like as done in asp.net to search for some control on a Page. How can I do this

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• Programming languages: out of the box legibility and extensibility

  - by sova

  Two excellent results of SOLID development ideology are - Legibility - Extensibility over the life of a project (http://en.m.wikipedia.org/wiki/Solid_(object-oriented_design) Although SOLID is a set of language-agnostic design ideas, some languages inherently support these ideas better than others. Out-of-the-box or after various customizations, in your opinion which language is best-suited to be both easily readable and easy to extend functionality in? Some definitions to pre-empt biases and flamewars: Legibility: amount of thinking done to understand the code proportional to the amount of code: (amount_think-energy / amount_code) is fairly constant and as low as possible in the optimal case. Extensibility: Addition of X amount of functionality requires a change in code or code additions in proportion to X (amount_added_functionality / amount_added_code) is fairly constant and as high as possible in the optimal case. Supporting information and tutorials encouraged. Code snippets welcome.

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• undefined reference

  - by rantravee

  Hi, I'm unfamiliar to working in c++ under linux so I have some issues, one of them is that after I write a class and try to instantiate an object of that class I get to following error : "undefined reference to Constructor_of_that_class" . This happens for every class that I write , and it happens no matter where I try to do the instantiating, even if the code compiles without any problems . What is going wrong here and what I have to do to get over this error ? Because the project that I'm working wasn't created by me I suspect that it has to do something with some settings but I don't know which.

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• Linker Error: iPhone Unit Test Bundle referencing App classes

  - by ohhorob

  Starting with an app already in development, I have carried out the instructions in the iPhone Development Guide – Unit Testing Applications I can successfully include and use my App's classes in Application-style tests that run on the device, and output their results to the console. If I add the following line of code: STAssertTrue([viewController isKindOfClass:[LoginViewController class]], @"Top view controller is not LoginViewController"); The following build error is generated: Undefined symbols: "_OBJC_CLASS_$_LoginViewController", referenced from: __objc_classrefs__DATA@0 in LoginViewTest.o ld: symbol(s) not found collect2: ld returned 1 exit status I can provide more configuration information for the project and the Testing target, but the setup works file without the [LoginViewController class] line in the test source. Without that line, I can reference the class, use it's properties and send it messages successfully. Is there a linking build setting, or bundle loading option that is required when attempting to use an App class in this fashion? Or should I find another type of test to confirm that the class of an object is the expected one?

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• Speed up the loop operation in R

  - by Kay

  Hi, i have a big performance problem in R. I wrote a function that iterates over an data.frame object. It simply adds a new col to a data.frame and accumulate sth. (simple operation). The data.frame has round about 850.000 rows. My PC is still working about 10h now and i have no idea about the runtime. dayloop2 <- function(temp){ for (i in 1:nrow(temp)){ temp[i,10] <- i if (i > 1) { if ((temp[i,6] == temp[i-1,6]) & (temp[i,3] == temp[i-1,3])) { temp[i,10] <- temp[i,9] + temp[i-1,10] } else { temp[i,10] <- temp[i,9] } } else { temp[i,10] <- temp[i,9] } } names(temp)[names(temp) == "V10"] <- "Kumm." return(temp) } Any ideas how to speed up this operation ?

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• Facebook Scrumptious sample app won't build

  - by Chase Roberts

  I did exactly what they do in the video. However, when I get to the scrumptious app and try to build/run it, mine fails. It says: "Parse Issue. Expected a type." Here are the two lines that it thinks are broken (located in the ACAccountStore.h): // Returns the account type object matching the account type identifier. See // ACAccountType.h for well known account type identifiers - (ACAccountType *)accountTypeWithAccountTypeIdentifier:(NSString *)typeIdentifier; // Returns the accounts matching a given account type. - (NSArray *)accountsWithAccountType:(ACAccountType *)accountType; Here is a link to the tutorial. I only didn't even make it two min in before I hit this wall. http://developers.facebook.com/docs/getting-started/facebook-sdk-for-ios/3.1/ I am running Xcode v4.4.1.

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• super() in Python 2.x without args

  - by Slava Vishnyakov

  Trying to convert super(B, self).method() into a simple nice bubble() call. Did it, see below! Is it possible to get reference to class B in this example? class A(object): pass class B(A): def test(self): test2() class C(B): pass import inspect def test2(): frame = inspect.currentframe().f_back cls = frame.[?something here?] # cls here should == B (class) c = C() c.test() Basically, C is child of B, B is child of A. Then we create c of type C. Then the call to c.test() actually calls B.test() (via inheritance), which calls to test2(). test2() can get the parent frame frame; code reference to method via frame.f_code; self via frame.f_locals['self']; but type(frame.f_locals['self']) is C (of course), but not B, where method is defined. Any way to get B?

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• Exception while trying to deserialize JSON into EntityFramework using JavaScriptSerializer

  - by Barak

  I'm trying to deserialize JSON which I'm getting from an external source into an Entity Framework entity class using the following code: var serializer = new JavaScriptSerializer(); IList<Feature> obj = serializer.Deserialize<IList<Feature>>(json); The following exception is thrown: Object of type 'System.Collections.Generic.List1[JustTime.Task]' cannot be converted to type 'System.Data.Objects.DataClasses.EntityCollection1[JustTime.Task]'. My model is simple: The Feature class has a one-to-many relation to the Tasks class. The problem appears to be the deserializer is trying to create a generic List to hold the collection of tasks instead of an EntityCollection. I've tried implementing a JavaScriptConverted which would handle System.Collections.Generic.List but it didn't get called by the deserializer.

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• Tracking EXC_BAD_ACCESS on iPad

  - by Aleks

  I've been using this code to create my UIWindow UIMyWindow* win = [[UIMyWindow alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; UIMyWindow isn't anything special it just has a pointer to a C++ class that does some wrapping of ObjectiveC. Recently my application start crashing after adding some line of code that doesn't have to do anything with the error. The line of code that I added is just allocating a C++ object but the program execution never reaches this line. Interesting enough my code works in Release. My only guess is that I made some memory corruption on a completely different place. My questions are: What type of memory corruption that can be? And is there some good practices to track them down?

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