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  • Why in Objective-C, we use self = [super init] instead of just [super init]?

    - by ????
    In a book, I saw that if a subclass is overriding a superclass's method, we may have self = [super init]; First, is this supposed to be done in the subclass's init method? Second, I wonder why the call is not just [super init]; ? I mean, at the time of calling init, the memory is allocated by alloc already (I think by [Foobar alloc] where Foobar is the subclass's name. So can't we just call [super init] to initialize the member variables? Why do we have to get the return value of init and assign to self? I mean, before calling [super init], self should be pointing to a valid memory allocation chuck... so why assigning something to self again? (if assigning, won't [super init] just return self's existing value?)

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  • Claims-based Authentication: Are strings the essence of claims?

    - by Rising Star
    I've been programming with claims-based authentication for some time now with Windows Identity Foundation. It appears to me that in Windows Identity Foundation, once a user is logged in, the claims are basically strings of information that describe the user. With the old role-based authentication, I could say that a user is or is not a member of a given group, but with claims-based authentication, I can now have strings of information that describe a user. "This user is female". This user was born on "July 6, 1975". "This user logged in using a USB key". Is it the essence of claims-based authentication,that I have strings of information about the user given to the application by the framework?

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  • Binding to a List<object> in silverlight problem.

    - by cw
    Hello, Can someone suggest what I am doing wrong? Basically I have a List Items, when an item gets added to the list I am resetting the collection to the viewmodel property. The only way I can get it to work is if I null the member object out before reassigning the binding. Any suggestions on how to go about updating a UI when an item gets added to a List? public List<Item> RegisteredItems { get { return m_vRegisteredItems; } set { m_vRegisteredItems= null; NotifyPropertyChanged("RegisteredItems"); m_vRegisteredItems= value; NotifyPropertyChanged("RegisteredItems"); } }

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  • Question about the mathematical properties of hashes

    - by levand
    Take a commonly used binary hash function - for example, SHA-256. As the name implies, it outputs a 256 bit value. Let A be the set of all possible 256 bit binary values. A is extremely large, but finite. Let B be the set of all possible binary values. B is infinite. Let C be the set of values obtained by running SHA-256 on every member of B. Obviously this can't be done in practice, but I'm guessing we can still do mathematical analysis of it. My Question: By necessity, C ? A. But does C = A?

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  • What do you tell people your profession is? [closed]

    - by user110296
    My technical title is Member of the Technical Staff, and like you most of you, I design/write code for a living. I can never decide what to answer when someone asks what I do for a living? Software Developer? Software Engineer? [Kernel] Programmer? Computer Scientist? These all seem to have various bad connotations. I guess I like Software Engineer the best, but unfortunately this term has been coopted by people who don't actually code. I made the mistake of taking a 'Software Engineering' class, and realized that I definitely don't want to be associated with people who major in this. Probably this is too subjective, so feel free to community wiki it or whatever, but I think it is a valid question and I would like to hear what others have decided on and their reasoning.

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  • Templates --> How to decipher, decide if necessary and create?

    - by ML
    Hi All, I have a few classes in a project that I inherited that are really old, last I knew they compiled with CodeWarrior 8. I am not in XCode 3.2 Here is an example of what I struggle with: template <class registeredObject> typename std::vector<registeredObject>::iterator FxRegistry<registeredObject>::begin(void) { return mRegistryList.begin(); } The errors are: no 'typename std::vector<registeredObject, std::allocator<_CharT> >::iterator FxRegistry<registeredObject>::begin()' member function declared in class 'FxRegistry<registeredObject>' template definition of non-template 'typename std::vector<registeredObject, std::allocator<_CharT> >::iterator FxRegistry<registeredObject>::begin()' How do I decide how to solve these and where do I start looking?

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  • Why is the 'this' keyword not a reference type in C++ [closed]

    - by Dave Tapley
    Possible Duplicates: Why ‘this’ is a pointer and not a reference? SAFE Pointer to a pointer (well reference to a reference) in C# The this keyword in C++ gets a pointer to the object I currently am. My question is why is the type of this a pointer type and not a reference type. Are there any conditions under which the this keyword would be NULL? My immediate thought would be in a static function, but Visual C++ at least is smart enough to spot this and report static member functions do not have 'this' pointers. Is this in the standard?

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  • iphone: Implement delegate in class

    - by Nic Hubbard
    I am trying to call up a modal table view controller using presentModalViewController but I am not sure what to do about the delegate. The following code gives me an error: MyRidesListView *controller = [[MyRidesListView alloc] init]; controller.delegate = self; [self presentModalViewController:controller animated:YES]; [controller release]; Error: Request for member 'delegate' is something not a structure or union Now, I realized there is no delegate property in my MyRidesListView class. So, how would I add a reference to my delegate there? What am I missing here?

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  • When loading shopping cart in Magento with a new Payment module, I get an error I haven't been able

    - by Joseph
    I am trying to add a new payment module into Magento. However, even after commenting out the vast majority of the code, I still get the following error: Fatal error: Call to a member function isAvailable() on a non-object in /var/www/html/app/code/core/Mage/Payment/Helper/Data.php on line 71 I am using Magento 1.4.0.1, and have disabled the cache. I even emptied the cache several times just in case. The only code currently not commented out is based on the tutorials here and here. The error occurs when the cart is loaded either from the administration area or the front end. Is there anyone out there that has run into a similar issue? I would post code, but I am not sure what needs to be posted. Thanks for the assistance.

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  • Ripping a CD to mp3 in C# - third party component or api out there?

    - by Jonathan Williamson
    We're working on a project that requires the ripping of audio tracks from CDs to MP3s (ideally also retrieving the track information from CDDB or similar). More background information: Various music labels send us CDs of music which we then deliver to people via an online delivery system. We're looking at automating the process of converting those CDs into MP3s with full track information where possible. We want to produce a simple desktop application that allows a member of editorial staff to setup the information about the new music we receive. To streamline the process we'd like to include the ripping of the audio and retrieval of the track information.

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  • Link a programmatic instantiation of class x in class y to a view controller of class x

    - by Joel Derfner
    I have classes Compose and Haiku, each connected to a view controller in IB. Haiku is instantiated in Compose as ghhaiku. Haiku has an array, self.arrayOfHaiku, with 117 members. But in Compose, self.ghhaiku.arrayOfHaiku has no members. I think the problem is that I haven't linked the instance of Haiku that has the 117-member array with the instance of Haiku created in Compose. But how do I do that? (I could of course be totally wrong and the problem could be something else, but that seems to make intuitive sense.) Any thoughts?

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  • How to give position zero of spinner a prompt value?

    - by Eugene H
    The database is then transferring the data to a spinner which I want to leave position 0 blank so I can add a item to the spinner with no value making it look like a prompt. I have been going at it all day. FAil after Fail MainActivity public class MainActivity extends Activity { Button AddBtn; EditText et; EditText cal; Spinner spn; SQLController SQLcon; ProgressDialog PD; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); AddBtn = (Button) findViewById(R.id.addbtn_id); et = (EditText) findViewById(R.id.et_id); cal = (EditText) findViewById(R.id.et_cal); spn = (Spinner) findViewById(R.id.spinner_id); spn.setOnItemSelectedListener(new OnItemSelectedListenerWrapper( new OnItemSelectedListener() { @Override public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) { SQLcon.open(); Cursor c = SQLcon.readData(); if (c.moveToPosition(pos)) { String name = c.getString(c .getColumnIndex(DBhelper.MEMBER_NAME)); String calories = c.getString(c .getColumnIndex(DBhelper.KEY_CALORIES)); et.setText(name); cal.setText(calories); } SQLcon.close(); // closing database } @Override public void onNothingSelected(AdapterView<?> parent) { // TODO Auto-generated method stub } })); SQLcon = new SQLController(this); // opening database SQLcon.open(); loadtospinner(); AddBtn.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { new MyAsync().execute(); } }); } public void loadtospinner() { ArrayList<String> al = new ArrayList<String>(); Cursor c = SQLcon.readData(); c.moveToFirst(); while (!c.isAfterLast()) { String name = c.getString(c.getColumnIndex(DBhelper.MEMBER_NAME)); String calories = c.getString(c .getColumnIndex(DBhelper.KEY_CALORIES)); al.add(name + ", Calories: " + calories); c.moveToNext(); } ArrayAdapter<String> aa1 = new ArrayAdapter<String>( getApplicationContext(), android.R.layout.simple_spinner_item, al); spn.setAdapter(aa1); // closing database SQLcon.close(); } private class MyAsync extends AsyncTask<Void, Void, Void> { @Override protected void onPreExecute() { super.onPreExecute(); PD = new ProgressDialog(MainActivity.this); PD.setTitle("Please Wait.."); PD.setMessage("Loading..."); PD.setCancelable(false); PD.show(); } @Override protected Void doInBackground(Void... params) { String name = et.getText().toString(); String calories = cal.getText().toString(); // opening database SQLcon.open(); // insert data into table SQLcon.insertData(name, calories); return null; } @Override protected void onPostExecute(Void result) { super.onPostExecute(result); loadtospinner(); PD.dismiss(); } } } DataBase public class SQLController { private DBhelper dbhelper; private Context ourcontext; private SQLiteDatabase database; public SQLController(Context c) { ourcontext = c; } public SQLController open() throws SQLException { dbhelper = new DBhelper(ourcontext); database = dbhelper.getWritableDatabase(); return this; } public void close() { dbhelper.close(); } public void insertData(String name, String calories) { ContentValues cv = new ContentValues(); cv.put(DBhelper.MEMBER_NAME, name); cv.put(DBhelper.KEY_CALORIES, calories); database.insert(DBhelper.TABLE_MEMBER, null, cv); } public Cursor readData() { String[] allColumns = new String[] { DBhelper.MEMBER_ID, DBhelper.MEMBER_NAME, DBhelper.KEY_CALORIES }; Cursor c = database.query(DBhelper.TABLE_MEMBER, allColumns, null, null, null, null, null); if (c != null) { c.moveToFirst(); } return c; } } Helper public class DBhelper extends SQLiteOpenHelper { // TABLE INFORMATTION public static final String TABLE_MEMBER = "member"; public static final String MEMBER_ID = "_id"; public static final String MEMBER_NAME = "name"; public static final String KEY_CALORIES = "calories"; // DATABASE INFORMATION static final String DB_NAME = "MEMBER.DB"; static final int DB_VERSION = 2; // TABLE CREATION STATEMENT private static final String CREATE_TABLE = "create table " + TABLE_MEMBER + "(" + MEMBER_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + MEMBER_NAME + " TEXT NOT NULL," + KEY_CALORIES + " INT NOT NULL);"; public DBhelper(Context context) { super(context, DB_NAME, null, DB_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(CREATE_TABLE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub db.execSQL("DROP TABLE IF EXISTS " + TABLE_MEMBER); onCreate(db); } }

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  • C++ constant reference lifetime

    - by aaa
    hello I have code that looks like this: class T {}; class container { const T &first, T &second; container(const T&first, const T & second); }; class adapter : T {}; container(adapter(), adapter()); I thought lifetime of constant reference would be lifetime of container. However, it appears otherwise, adapter object is destroyed after container is created, leading dangling reference. What is the correct lifetime? how to correctly implement binding temporary object to class member reference? Thanks

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  • Understanding "this" keyword

    - by Raffaele
    In this commit there is a change I cannot explain deferred.done.apply( deferred, arguments ).fail.apply( deferred, arguments ); becomes deferred.done( arguments ).fail( arguments ); AFAIK, when you invoke a function as a member of some object like obj.func(), inside the function this is bound to obj, so there would be no use invoking a function through apply() just to bound this to obj. Instead, according to the comments, this was required because of some preceding $.Callbacks.add implementation. My doubt is not about jQuery, but about the Javascript language itself: when you invoke a function like obj.func(), how can it be that inside func() the this keyword is not bound to obj?

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  • C++ associative array with arbitrary types for values

    - by Gerald Kaszuba
    What is the best way to have an associative array with arbitrary value types for each key in C++? Currently my plan is to create a "value" class with member variables of the types I will be expecting. For example: class Value { int iValue; Value(int v) { iValue = v; } std::string sValue; Value(std::string v) { sValue = v; } SomeClass *cValue; Value(SomeClass *v) { cValue = c; } }; std::map<std::string, Value> table; A downside with this is you have to know the type when accessing the "Value". i.e.: table["something"] = Value(5); SomeClass *s = table["something"].cValue; // broken pointer Also the more types that are put in Value, the more bloated the array will be. Any better suggestions?

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  • Create a link to delete membership in web2py

    - by user1741325
    I'm trying to do something really simple but it's taking me ages to figure out how to do it properly. I want to have a button that simply deletes a member from a group. So in my view I have <div id="del-role">{{=A('Delete Role',_class="btn btn-danger", callback=URL('test'),delete='#del-role')}}</div> However, when I click the button, the only thing I get is a Javascript prompt asking whether I'm sure I want to delete the specified object, yes/no. That's fine but, what I'd really like to do is just auth.del_membership('role') What needs to go in my controller? I do not want any page redirection, I just want to auth.del_membership(role) This seemingly simple thing is taking me forever to understand. Thanks!

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  • Sql Server as logging, best connection practise

    - by ozz
    I'm using SqlServer as logging. Yes this is wrong decision, there are better dbs for this requirement. But I have no other option for now. Logging interval is 3 logs per second. So I've static Logger class and it has static Log method. Using "Open Connection" as static member is better for performance. But what is the best implemantation of it? This is not that I know. public static class OzzLogger { static SqlConnection Con; static OzzLogger() { Con=ne SqlConnection(....); Con.Open(); } public static void Log(....) { Con.ExecuteSql(......); } } UPDATE I asked because of my old information. People say "connection pooling performance is enough". If there is no objection I'm closing the issue :)

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  • Parsing String into multiple variable length String (C#)

    - by Nassign
    I am currently trying to convert a VB6 program into C#. There was extensive use of string splitting into structure. For example, Dim Sample AS String Sample = "John Doe New York Test Comment" Public Type Struct1 Name As String * 15 Address As String * 10 Comment As String * 20 End Type Dim dataStruct As Struct1 Set dataStruct = Sample When the dataStruct is set, it will automatically split value into the 3 structure member. Is there a special function to do this in C#. The only way I know how to do this is thru Attributes/Annotation describing the length and start position of string. Any other suggestion?

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  • Using a class with const data members in a vector

    - by Max
    Given a class like this: class Foo { const int a; }; Is it possible to put that class in a vector? When I try, my compiler tells me it can't use the default assignment operator. I try to write my own, but googling around tells me that it's impossible to write an assignment operator for a class with const data members. One post I found said that "if you made [the data member] const that means you don't want assignment to happen in the first place." This makes sense. I've written a class with const data members, and I never intended on using assignment on it, but apparently I need assignment to put it in a vector. Is there a way around this that still preserves const-correctness?

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  • Possible for C++ template to check for a function's existence?

    - by andy
    Is it possible to write a C++ template that changes behavior depending on if a certain member function is defined on a class? Here's a simple example of what I would want to write: template<class T> std::string optionalToString(T* obj) { if (FUNCTION_EXISTS(T->toString)) return obj->toString(); else return "toString not defined"; } So if class T has "toString" defined then it uses it, otherwise it doesn't. The magical part that I don't know how to do is the "FUNCTION_EXISTS" part.

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  • Should downcasting be avoided while using a class hierarchy in C++?

    - by neuviemeporte
    Let's say I'm writing an application which works with projects, and exposes different functionality depending on the type of the project. I have a hierarchy of classes for the different types of projects: class AbstractProject { }; class ProjectA : public AbstractProject { }; class ProjectB : public AbstractProject { }; class ProjectC : public AbstractProject { }; Now, I was planning to have an AbstractProject *_currentProject pointer as a member in the application's main class, pop up a dialog box on startup and based on the selection, do: _currentProject = new ProjectB(); // e.g. Later, I'll have to downcast the pointer to the specific type to utilize the functionality specific to different Project-s. Somehow this makes me feel uneasy. Is there a Better Way of doing this?

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  • class which cannot be derived

    - by benjamin button
    I found this code here class Usable; class Usable_lock { friend class Usable; private: Usable_lock() {} Usable_lock(const Usable_lock&) {} }; class Usable : public virtual Usable_lock { // ... public: Usable(); Usable(char*); // ... }; Usable a; class DD : public Usable { }; DD dd; // error: DD::DD() cannot access // Usable_lock::Usable_lock(): private member Could anybody explain me this code?

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  • How do I release an object allocated in a different AutoReleasePool ?

    - by ajcaruana
    Hi, I have a problem with the memory management in Objective-C. Say I have a method that allocates an object and stores the reference to this object as a member of the class. If I run through the same function a second time, I need to release this first object before creating a new one to replace it. Supposing that the first line of the function is: NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; This means that a different auto-release pool will be in place. The code to allocate the object is as follows: if (m_object != nil) [m_object release]; m_object = [[MyClass alloc] init]; [m_object retain]; The problem is that the program crashes when running the last line of the method: [pool release]; What am I doing wrong ? How can I fix this ? Regards Alan

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  • mysql stored procedures using php

    - by neo skosana
    I have a stored procedure: delimiter // create procedure userlogin(in eml varchar(50)) begin select * from users where email = eml; end// delimiter ; And the php: $db = new mysqli("localhost","root","","houseDB"); $eml = "[email protected]"; $sql = $db-query("CALL userlogin('$eml')"); $result = $sql-fetch_array(); The error that I get from the browser when I run the php script: Fatal error: Call to a member function fetch_array() on a non-object... I am using phpmyadmin version 3.2.4 and mysql client version 5.1.41. Please help. Thank you.

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  • Suggestions for performance improvement surrounding sending email notifications?

    - by jcmoney
    It takes around a couple of seconds for my app to execute the code to send an email right now on a test server with nothing much else running. Not sure if this is typical/expected. I'm also using the php framework Kohana's email helper and not php's mail directly out of convenience if that matters. Is it always just better to schedule a cron job to send emails every 5 min or so? Or should I be able to send emails immediately and I'm just not doing something right? What the script does is insert a row into the db and notifies the relevant group that the row was created. The groups are usually < 20 people so I just do a loop calling Kohana's email helper each time for each member of the group.

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