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  • Design pattern for extending Android's activities?

    - by Carl
    While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

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  • How should I handle expected errors? eg. "username already exists"

    - by Pheter
    I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?

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  • Is Assert.Fail() considered bad practice?

    - by Mendelt
    I use Assert.Fail a lot when doing TDD. I'm usually working on one test at a time but when I get ideas for things I want to implement later I quickly write an empty test where the name of the test method indicates what I want to implement as sort of a todo-list. To make sure I don't forget I put an Assert.Fail() in the body. When trying out xUnit.Net I found they hadn't implemented Assert.Fail. Of course you can always Assert.IsTrue(false) but this doesn't communicate my intention as well. I got the impression Assert.Fail wasn't implemented on purpose. Is this considered bad practice? If so why? @Martin Meredith That's not exactly what I do. I do write a test first and then implement code to make it work. Usually I think of several tests at once. Or I think about a test to write when I'm working on something else. That's when I write an empty failing test to remember. By the time I get to writing the test I neatly work test-first. @Jimmeh That looks like a good idea. Ignored tests don't fail but they still show up in a separate list. Have to try that out. @Matt Howells Great Idea. NotImplementedException communicates intention better than assert.Fail() in this case @Mitch Wheat That's what I was looking for. It seems it was left out to prevent it being abused in another way I abuse it.

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  • What are the constraints on Cocoa Framework version numbers?

    - by Joe
    We're distributing a Cocoa framework with regular updates. We'll be updating the version numbers with each release. The Apple documentation appears to suggest that version numbers should be consecutive incrementing integers. We are distributing output in several formats, and the framework is only one of them. We would rather not have to maintain a separate numbering system just for our frameworks. We don't really care about the precise format of the version numbers of the framework, so long as they change whenever the product changes, and behave in a correct and expected manner. I'm looking for a sensible and correct way of avoiding having to run a separate version number counter. One suggestion is that for product version 12.34.56 we could simply remove the dots and say the framework version is 123456. Is there a constraint on the type of number that can be represented (uint? long?) Does it have to be a number? Could it be a string? Do the numbers have to be consecutive? Is there a standard way of doing things in this situation?

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  • Javascript clarity of purpose

    - by JesDaw
    Javascript usage has gotten remarkably more sophisticated and powerful in the past five years. One aspect of this sort of functional programming I struggle with, esp with Javascript’s peculiarities, is how to make clear either through comments or code just what is happening. Often this sort of code takes a while to decipher, even if you understand the prototypal, first-class functional Javascript way. Any thoughts or techniques for making perfectly clear what your code does and how in Javascript? I've asked this question elsewhere, but haven't gotten much response.

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  • Should I make sure arguments aren't null before using them in a function.

    - by Nathan W
    The title may not really explain what I'm really trying to get at, couldn't really think of a way to describe what I mean. I was wondering if it is good practice to check the arguments that a function accepts for nulls or empty before using them. I have this function which just wraps some hash creation like so. Public Shared Function GenerateHash(ByVal FilePath As IO.FileInfo) As String If (FilePath Is Nothing) Then Throw New ArgumentNullException("FilePath") End If Dim _sha As New Security.Cryptography.MD5CryptoServiceProvider Dim _Hash = Convert.ToBase64String(_sha.ComputeHash(New IO.FileStream(FilePath.FullName, IO.FileMode.Open, IO.FileAccess.Read))) Return _Hash End Function As you can see I just takes a IO.Fileinfo as an argument, at the start of the function I am checking to make sure that it is not nothing. I'm wondering is this good practice or should I just let it get to the actual hasher and then throw the exception because it is null.? Thanks.

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  • How to face observable object containing an observable field

    - by iseek
    Hello, I need a hint concerning MVC and Observer-Pattern. For example a model contains the classes "Address" and "Person". The Address class contains the fields street:String, zipcode:String, location:String. Whereas the Person class contains the fields name:String, firstName:String, address:Address. My approach so far looks something like this: Both, Address and Person are observable. If one of their setters is being called, I validate whether the current value and new value differ. Only in this case an update event is fired. The event contains the source, the name of the changed field, the old and the new value. The class for the view contains text fields to display and edit the information of a person: name, firstname, street, zipcode, location. It knows the Person model and is an subscribed observer for the person. So it gets the update events from the person object. My questions concerns the address field from type Address in the person class, since an address is observable on its own. If the view gets an update event from person when a new address has been set, I can update all of the address related fields in the view. But what if a field of the address changes? Should the view also register for update events from the address? Any hints about common design approaches would be appreciated. Greetings.

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  • How to use interfaces in exception handling

    - by vikp
    Hi, I'm working on the exception handling layer for my application. I have read few articles on interfaces and generics. I have used inheritance before quite a lot and I'm comfortable with in that area. I have a very brief design that I'm going to implement: public interface IMyExceptionLogger { public void LogException(); // Helper methods for writing into files,db, xml } I'm slightly confused what I should be doing next. public class FooClass: IMyExceptionLogger { // Fields // Constructors } Should I implement LogException() method within FooClass? If yes, than I'm struggling to see how I'm better of using an interface instead of the concrete class... I have a variety of classes that will make a use of that interface, but I don't want to write an implementation of that interface within each class. In the same time If I implement an interface in one class, and then use that class in different layers of the application I will be still using concrete classes instead of interfaces, which is a bad OO design... I hope this makes sense. Any feedback and suggestions are welcome. Please notice that I'm not interested in using net4log or its competitors because I'm doing this to learn. Thank you Edit: Wrote some more code. So I will implement variety of loggers with this interface, i.e. DBExceptionLogger, CSVExceptionLogger, XMLExceptionLogger etc. Than I will still end up with concrete classes that I will have to use in different layers of my application.

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  • How to test a site rigorously?

    - by Sarfraz
    Hello, I recently created a big portal site. It's time for putting it to test. How do you guys test a site rigorously? What are the ways and tools for that? Can we sort of mimic hundreds of virtual users visiting the site to see its load handling? The test should be for both security and speed Thanks in advance.

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  • Constructor Overload Problem in C++ Inherrentance

    - by metdos
    Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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  • Howto mix TDD and RAII

    - by f4
    I'm trying to make extensive tests for my new project but I have a problem. Basically I want to test MyClass. MyClass makes use of several other class which I don't need/want to do their job for the purpose of the test. So I created mocks (I use gtest and gmock for testing) But MyClass instantiate everything it needs in it's constructor and release it in the destructor. That's RAII I think. So I thought, I should create some kind of factory, which creates everything and gives it to MyClass's constructor. That factory could have it's fake for testing purposes. But's thats no longer RAII right? Then what's the good solution here?

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  • How to check for undefined or null variable in javascript

    - by Thomas Wanner
    We are frequently using the following code pattern in our javascript code if(typeof(some_variable) != 'undefined' && some_variable != null) { // do something with some_variable } and I'm wondering whether there is a less verbose way of checking that has the same effect. According to some forums and literature saying simply if(some_variable) { // do something with some_variable } should have the same effect. Unfortunately, Firebug evaluates such a statement as error on runtime when some_variable is undefined, whereas the first one is just fine for him. Is this only an (unwanted) behavior of Firebug or is there really some difference between those two ways ?

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  • Is it OK to write code after [super dealloc]? (Objective-C)

    - by Richard J. Ross III
    I have a situation in my code, where I cannot clean up my classes objects without first calling [super dealloc]. It is something like this: // Baseclass.m @implmentation Baseclass ... -(void) dealloc { [self _removeAllData]; [aVariableThatBelongsToMe release]; [anotherVariableThatBelongsToMe release]; [super dealloc]; } ... @end This works great. My problem is, when I went to subclass this huge and nasty class (over 2000 lines of gross code), I ran into a problem: when I released my objects before calling [super dealloc] I had zombies running through the code that were activated when I called the [self _removeAllData] method. // Subclass.m @implementation Subclass ... -(void) deallloc { [super dealloc]; [someObjectUsedInTheRemoveAllDataMethod release]; } ... @end This works great, and It didn't require me to refactor any code. My question Is this: Is it safe for me to do this, or should I refactor my code? Or maybe autorelease the objects? I am programming for iPhone if that matters any.

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  • Well written open source java projects

    - by Algorist
    I want to improve my design and programming skills by understanding design & code of open source projects. I downloaded hadoop,groovy but they are very difficult to follow. I am not having a clue of how to follow this code without having a high level overview of the design. Any suggestions?? Thank you.

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  • Learning Javascript in one weekend?

    - by dueyfinster
    Similiar to this question, I am wondering if experienced Javascript developers have any websites they use with examples to get the basics of Javascript down in 24/28 hours? I have looked at Douglas Crockford's Google Tech Talk and I bought the book "Javascript: the good parts" but I haven't had time to read it.

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  • Why do I need to give my options a value attribute in my dropdown? JQuery related.

    - by Alex
    So far in my web developing experiences, I've noticed that almost all web developers/designers choose to give their options in a select a value like so: <select name="foo"> <option value="bar">BarCheese</option> // etc. // etc. </select> Is this because it is best practice to do so? I ask this because I have done a lot of work with jQuery and dropdown's lately, and sometimes I get really annoyed when I have to check something like: $('select[name=foo]').val() == "bar"); To me, many times that seems less clear than just being able to check the val() against BarCheese. So why is it that most web developers/designers specify a value paramater instead of just letting the options actual value be its value? And yes, if the option has a value attribute I know I can do something like this: $('select[name=foo] option:contains("BarCheese")').attr('selected', 'selected'); But I would still really like to know why this is done. Thanks!!

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  • TCP Message Structure with XML

    - by metdos
    Hello Everybody, I'm sending messages over TCP/IP and on the other side I parse TCP message.For example this is one of the sent messages. $DKMSG(requestType=REQUEST_LOGIN&requestId=123&username=metdos&password=123)$EDKMSG Clarification: $DKMSG( //Start )$EDKMSG //End requestType //Parameter REQUEST_LOGIN //Parameter Value Now I also want to add an Xml file to my message. I'm considering this option: $DKMSG(requestType=REQUEST_LOGIN&xmlData= <Item id="56D@MIT" type="SIGNAL"> <Label> <Text>56D</Text> <X1>10</X1> <Y1>40</Y1> <RotateAngle>90</RotateAngle> </Label> <X1>0</X1> <Y1>20</Y1> <Width>35</Width> <Height>10</Height> <Source>sgs3lr</Source> </Item> )$EDKMSG There are problems with this way: 1-)It doesn't seem right to me. 2-)I have to handle delimeter "=" with much more care or I need to change it in parameters. What are your suggestions, thanks.

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  • Sending object C from class A to class B

    - by user278618
    Hi, I can't figure out how to design classes in my system. In classA I create object selenium (it simulates user actions at website). In this ClassA I create another objects like SearchScreen, Payment_Screen and Summary_Screen. # -*- coding: utf-8 -*- from selenium import selenium import unittest, time, re class OurSiteTestCases(unittest.TestCase): def setUp(self): self.verificationErrors = [] self.selenium = selenium("localhost", 5555, "*chrome", "http://www.someaddress.com/") time.sleep(5) self.selenium.start() def test_buy_coffee(self): sel = self.selenium sel.open('/') sel.window_maximize() search_screen=SearchScreen(self.selenium) search_screen.choose('lavazza') payment_screen=PaymentScreen(self.selenium) payment_screen.fill_test_data() summary_screen=SummaryScreen(selenium) summary_screen.accept() def tearDown(self): self.selenium.stop() self.assertEqual([], self.verificationErrors) if __name__ == "__main__": unittest.main() It's example SearchScreen module: class SearchScreen: def __init__(self,selenium): self.selenium=selenium def search(self): self.selenium.click('css=button.search') I want to know if there is anything ok with a design of those classes?

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  • How can I sync three classes?

    - by TheMachineCharmer
    class Foo { Bar b; List<Foo> Neighbours; } class Bar { Spam s; List<Bar> Neighbours; } class Spam { List<string> Neighbours; } Each of these classes have AddNeighbour,RemoveNeighbour methods. User can add/remove Neighbours from any of the class at random. I want these three objects to be in sync. How can I do this?

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  • Is it Bad Practice to use C++ only for the STL containers?

    - by gmatt
    First a little background ... In what follows, I use C,C++ and Java for coding (general) algorithms, not gui's and fancy program's with interfaces, but simple command line algorithms and libraries. I started out learning about programming in Java. I got pretty good with Java and I learned to use the Java containers a lot as they tend to reduce complexity of book keeping while guaranteeing great performance. I intermittently used C++, but I was definitely not as good with it as with Java and it felt cumbersome. I did not know C++ enough to work in it without having to look up every single function and so I quickly reverted back to sticking to Java as much as possible. I then made a sudden transition into cracking and hacking in assembly language, because I felt I was concentrated too much attention on a much too high level language and I needed more experience with how a CPU interacts with memory and whats really going on with the 1's and 0's. I have to admit this was one of the most educational and fun experiences I've had with computers to date. For obviously reasons, I could not use assembly language to code on a daily basis, it was mostly reserved for fun diversions. After learning more about the computer through this experience I then realized that C++ is so much closer to the "level of 1's and 0's" than Java was, but I still felt it to be incredibly obtuse, like a swiss army knife with far too many gizmos to do any one task with elegance. I decided to give plain vanilla C a try, and I quickly fell in love. It was a happy medium between simplicity and enough "micromanagent" to not abstract what is really going on. However, I did miss one thing about Java: the containers. In particular, a simple container (like the stl vector) that expands dynamically in size is incredibly useful, but quite a pain to have to implement in C every time. Hence my code currently looks like almost entirely C with containers from C++ thrown in, the only feature I use from C++. I'd like to know if its consider okay in practice to use just one feature of C++, and ignore the rest in favor of C type code?

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  • How do I create a new AnyType[] array?

    - by cb
    Which is the best practice in this situation? I would like an un-initialized array of the same type and length as the original. public static <AnyType extends Comparable<? super AnyType>> void someFunction(AnyType[] someArray) { AnyType[] anotherArray = (AnyType[]) new Comparable[someArray.length]; ...or... AnyType[] anotherArray = (AnyType[]) new Object[someArray.length]; ...some other code... } Thanks, CB

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  • Best ways to reuse Java methods

    - by carillonator
    I'm learning Java and OOP, and have been doing the problems at Project Euler for practice (awesome site btw). I find myself doing many of the same things over and over, like: checking if an integer is prime/generating primes generating the Fibonacci series checking if a number is a palindrome What is the best way to store and call these methods? Should I write a utility class and then import it? If so, do I import a .class file or the .java source? I'm working from a plain text editor and the Mac terminal. Thanks!

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