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  • Using member variables inherited from a templated base class (C++)

    - by Aaron Becker
    I'm trying to use member variables of a templated base class in a derived class, as in this example: template <class dtype> struct A { int x; }; template <class dtype> struct B : public A<dtype> { void test() { int id1 = this->x; // always works int id2 = A<dtype>::x; // always works int id3 = B::x; // always works int id4 = x; // fails in gcc & clang, works in icc and xlc } }; gcc and clang are both very picky about using this variable, and require either an explicit scope or the explicit use of "this". With some other compilers (xlc and icc), things work as I would expect. Is this a case of xlc and icc allowing code that's not standard, or a bug in gcc and clang?

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  • C++ Constructor Initializer List - using member functions of initialized members

    - by Andy
    I've run into the following a few times with initializer lists and I've never been able to explain it well. Can anyone explain why exactly the following fails (I don't have a compiler to catch typos, so bear with me): class Foo { public: Foo( int i ) : m_i( i ) {} //works with no problem int getInt() {return m_i;} ~Foo {} private: int m_i; }; class Bar { public: Bar() : m_foo( 5 ), //this is ok m_myInt( m_foo.getInt() ) //runtime error, seg 11 {} ~Bar() {} private: Foo m_foo; int m_myInt; }; When trying to call member functions of members initialized higher up the initializer list, I get seg faults. I seem to recall this is a known problem (or perhaps somehow by design) but I've never seen it well described. The attached example is contrived with plain old data types, but substitute the Bar::m_myInt with another object lacking a default (empty) constructor and the issue is more real. Can anyone enlighten me? Thanks!

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  • Template meta-programming with member function pointers?

    - by wheaties
    Is it possible to use member function pointers with template meta-programming? Such as: class Connection{ public: string getName() const; string getAlias() const; //more stuff }; typedef string (Connection::*Con_Func)() const; template<Con_Func _Name> class Foo{ Connection m_Connect; public: void Foo(){ cout << m_Connect.(*_Name); } }; typedef Foo<&Connection::getName> NamedFoo; typedef Foo<&Connection::getAlias> AliasFoo; Granted, this is rather contrived but is it possible? (yes, there are probably much better ways but humor me.)

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  • C++: namespace conflict between extern "C" and class member

    - by plaisthos
    Hi, I stumbled upon a rather exotic c++ namespace problem: condensed example: extern "C" { void solve(lprec * lp); } class A { public: lprec * lp; void solve(int foo); } void A::solve(int foo) { solve(lp); } I want to call the c function solve in my C++ member function A::solve. The compiler is not happy with my intent: error C2664: 'lp_solve_ilp::solve' : cannot convert parameter 1 from 'lprec *' to 'int' Is there something I can prefix the solve function with? C::solve does not work

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  • Static member object of a class in the same class

    - by Luv
    Suppose we have a class as class Egg { static Egg e; int i; Egg(int ii):i(ii) {} Egg(const Egg &); //Prevents copy-constructor to be called public: static Egg* instance() {return &e} }; Egg Egg::e(47); This code guarantees that we cannot create any object, but could use only the static object. But how could we declare static object of the same class in the class. And also one thing more since e is a static object, and static objects can call only static member functions, so how could the constructor been called here for static object e, also its constructors are private.

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  • C++: namespace conflicht between extern "C" and class member

    - by plaisthos
    Hi, I stumbled upon a rather exotic c++ namespace problem: condensed example: extern "C" { void solve(lprec * lp); } class A { public: lprec * lp; void solve(int foo); } void A::solve(int foo) { solve(lp); } I want to call the c funcition solve in my C++ member function A::solve. The compiler is not happy with my intents: error C2664: 'lp_solve_ilp::solve' : cannot convert parameter 1 from 'lprec *' to 'int' Is there something I can prefix the solve function? C::solve does not work

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  • g_signal_connect error invalid use of member

    - by paultop6
    Hi Guys, More GTK questions, im trying to compile some code and im getting the following error: error: invalid use of member (did you forget the ‘&’ ?) This is comming from the g_signal_connect call: g_signal_connect ((gpointer) Drawing_Area_CPU, "expose-event", G_CALLBACK (graph_expose), NULL); Drawing_Area_CPU is a GtkWidget* and graph_expose is defined as: gboolean graph_expose(GtkWidget *widget, GdkEventExpose *event, gpointer data); So far as i can tell im doing everything right, but still i get this error. Can anyone help please? Regards Paul

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  • reference to XML file is not a member of the R file

    - by yoavstr
    how can i had to class layout in R another xml file ? it should b autmatic as i had new resources to res but it's not someone knows what i did wrong ? i open an activity and now i want to open another activity that will work with another xml example i have menu and main.xml now i want to go for anther activity called gamescreen using this method : newGameButton.setOnClickListener(new OnClickListener() { public void onClick(View view) { Intent i = = new Intent(this, gameScreen.class); startActivity(i); } } i want to move to another "page" to another activity called gameScreen which should b associated to the xml called gameScreen.xml but in his onCreate : public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.gameScreen); } and gameScreen is not a member of the R file please help me i am sitting for the last 4 hours felling like an idiot ...

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  • Programming terms - field, member, properties (C#)

    - by Petr
    Hi, I was trying to find meaning of this terms but especially due to language barrier I was not able to understand what they are used for. I assume that "field" is variable (object too?) in the class while "property" is just an object that returns specific value and cannot contain methods etc. By "member" I understand any object that is declared on the class level. But these are just my assumptions based on commented code samples where some careful programmers used "property region" etc. I would really appreciate if someone could explain it to me.

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  • The member [class] has no supported translation to SQL

    - by Code Sherpa
    Hi, I am getting the following error: Error Message:The member 'Company.ProductCore.Core.Domain.Account.Email' has no supported translation to SQL. My method looks like this: public Account GetAccountByEmail(string email) { Account account; using (WorkbookDataContext dc = _conn.GetContext()) { account = ( from a in dc.Accounts join em in dc.Emails on a.AccountId equals em.AccountId where a.Email.EmailAddress == email select a).FirstOrDefault(); } return account; } My Account class has a getter / setter that exposes Email: public Email Email { get { return _email; } set { _email = value; } } And my Email is a LINQ object. I have a feeling that the problem is that I am using a LINQ object for me Email property? I am new to LINQ and am not really sure why this is happening. Help appreciated, thanks...

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  • UDK "Error, Accessing a member of _'s within class through a context expression requires explicit 'O

    - by Ricket
    I get the following error in the UDK Frontend when I try to make my project: C:\UDK\UDK-2010-03\Development\Src\FixIt\Classes\ZInteraction.uc(58) : Error, Accessing a member of GameUISceneClient's within class through a context expression requires explicit 'Outer' The class ZInteraction extends Interaction. Line 58 is: GetSceneClient().ConsoleCommand("KEYNAME"@Key); What is the problem here? I am still investigating and I will update as I find out more. edit: Tried fixing the line up as class'UIRoot'.static.GetSceneClient().ConsoleCommand("KEYNAME"@Key); - no change.

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  • A pointer member variable having different values

    - by Rohan Prabhu
    Ok, to begin with, this is my code: HyperSprite::HyperSprite() { _view = 0; } void HyperSprite::publish(QGraphicsView* view) { _view = view; } void HyperSprite::getKFrame() { if(_view != 0) { qDebug()<<(void*)_view; } } Now, if I call HyperSprite::getKFrame() from within main(), I get the output: 0xbf8ffb84 I have a TCP server, which requires this QGraphicsView* variable. So whenever a new connection is made, HyperSprite::getKFrame() is called. However, whenever I make a connection to my server, this is the output: 0x1e425ff I honestly don't understand this. Shouldn't the value of a member remain same throughout? Why is the pointer value changing? As is obvious, whenever I try to use the _view pointer to access any of its members, a Segmentation Fault occurs. I tried using QSharedPointer, but it also results in the same problem. The data of the QSharedPointer automatically changes. Why is this happening?

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  • Getting the last member of a group on an intermediary M2M

    - by rh0dium
    If we look at the existing docs, what is the best way to get the last member added? This is similar to this but what I want to do is to be able to do this. group = Group.objects.get(id=1) group.get_last_member_added() #This is by ('-date_added') <Person: FOO> I think the best way is through a manager but how do you do this on an intermediary model? class Person(models.Model): name = models.CharField(max_length=128) def __unicode__(self): return self.name class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') def __unicode__(self): return self.name class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64)

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  • I having a problem with the mysqli free() member function

    - by neo skosana
    Hi I have code where I connected to the database like so: $db = new mysqli("localhost", "user", "pass", "company"); Now when I query the database like so: //query calls to a stored procedure 'user_info' $result = $db->query("CALL user_info('$instruc', 'c_register', '$eml', '$pass', '')"); //I use the $result This query works well. Now when I try and free that result like so: $result->free(); or $result->close(); It seems like it doesn't do anything because $result is still set. When I try to run another query it gives me this error: Fatal error: Call to a member function fetch_array() on a non-object in... For me to run this other query I have to close the db conection and connect again, then it will work. I want to know if there is a way I could run the other query without having to disconnect and reconnect to the database. thanks in advance.

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  • About Attributes member of LUID_AND_ATTRIBUTES used in TOKEN_PRIVILEGES structure

    - by Astaroth
    MSDN article, Enabling and Disabling Privileges in C++, provided the a code example to show how to enable or disable a privilege in an access token. I quote the part in questioned: tp.PrivilegeCount = 1; tp.Privileges[0].Luid = luid; if (bEnablePrivilege) tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED; else tp.Privileges[0].Attributes = 0; What is the meaning of zero value for Attributes member? According to the documentation of TOKEN_PRIVILEGES structure, the attributes of a privilege can be a combination of the following values: SE_PRIVILEGE_ENABLED  (it is 0x00000002L in WinNT.h) SE_PRIVILEGE_ENABLED_BY_DEFAULT  (it is 0x00000001L in WinNT.h) SE_PRIVILEGE_REMOVED  (it is 0x00000004L in WinNT.h) SE_PRIVILEGE_USED_FOR_ACCESS  (it is 0x80000000L in WinNT.h) So, we don't see any valid constant with a value of zero. I guess, the zero is equal to SE_PRIVILEGE_REMOVED. Anybody here could explain what the zero value really does?

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  • Member classes versus #includes

    - by ShallowThoughts
    I've recently discovered that it is bad form to have #includes in your header files because anyone who uses your code gets all those extra includes they won't necessarily want. However, for classes that have member variables defined as a type of another class, what's the alternative? For example, I was doing things the following way for the longest time: /* Header file for class myGrades */ #include <vector> //bad #include "classResult.h" //bad class myGrades { vector<classResult> grades; int average; int bestScore; } (Please excuse the fact that this is a highly artificial example) So, if I want to get rid of the #include lines, is there any way I can keep the vector or do I have to approach programming my code in an entirely different way?

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  • C++ non-member functions for nested template classes

    - by beldaz
    I have been writing several class templates that contain nested iterator classes, for which an equality comparison is required. As I believe is fairly typical, the comparison is performed with a non-member (and non-friend) operator== function. In doing so, my compiler (I'm using Mingw32 GCC 4.4 with flags -O3 -g -Wall) fails to find the function and I have run out of possible reasons. In the rather large block of code below there are three classes: a Base class, a Composed class that holds a Base object, and a Nested class identical to the Composed class except that it is nested within an Outer class. Non-member operator== functions are supplied for each. These classes are in templated and untemplated forms (in their own respective namespaces), with the latter equivalent to the former specialised for unsigned integers. In main, two identical objects for each class are compared. For the untemplated case there is no problem, but for the templated case the compiler fails to find operator==. What's going on? #include <iostream> namespace templated { template<typename T> class Base { T t_; public: explicit Base(const T& t) : t_(t) {} bool equal(const Base& x) const { return x.t_==t_; } }; template<typename T> bool operator==(const Base<T> &x, const Base<T> &y) { return x.equal(y); } template<typename T> class Composed { typedef Base<T> Base_; Base_ base_; public: explicit Composed(const T& t) : base_(t) {} bool equal(const Composed& x) const {return x.base_==base_;} }; template<typename T> bool operator==(const Composed<T> &x, const Composed<T> &y) { return x.equal(y); } template<typename T> class Outer { public: class Nested { typedef Base<T> Base_; Base_ base_; public: explicit Nested(const T& t) : base_(t) {} bool equal(const Nested& x) const {return x.base_==base_;} }; }; template<typename T> bool operator==(const typename Outer<T>::Nested &x, const typename Outer<T>::Nested &y) { return x.equal(y); } } // namespace templated namespace untemplated { class Base { unsigned int t_; public: explicit Base(const unsigned int& t) : t_(t) {} bool equal(const Base& x) const { return x.t_==t_; } }; bool operator==(const Base &x, const Base &y) { return x.equal(y); } class Composed { typedef Base Base_; Base_ base_; public: explicit Composed(const unsigned int& t) : base_(t) {} bool equal(const Composed& x) const {return x.base_==base_;} }; bool operator==(const Composed &x, const Composed &y) { return x.equal(y); } class Outer { public: class Nested { typedef Base Base_; Base_ base_; public: explicit Nested(const unsigned int& t) : base_(t) {} bool equal(const Nested& x) const {return x.base_==base_;} }; }; bool operator==(const Outer::Nested &x, const Outer::Nested &y) { return x.equal(y); } } // namespace untemplated int main() { using std::cout; unsigned int testVal=3; { // No templates first typedef untemplated::Base Base_t; Base_t a(testVal); Base_t b(testVal); cout << "a=b=" << testVal << "\n"; cout << "a==b ? " << (a==b ? "TRUE" : "FALSE") << "\n"; typedef untemplated::Composed Composed_t; Composed_t c(testVal); Composed_t d(testVal); cout << "c=d=" << testVal << "\n"; cout << "c==d ? " << (c==d ? "TRUE" : "FALSE") << "\n"; typedef untemplated::Outer::Nested Nested_t; Nested_t e(testVal); Nested_t f(testVal); cout << "e=f=" << testVal << "\n"; cout << "e==f ? " << (e==f ? "TRUE" : "FALSE") << "\n"; } { // Now with templates typedef templated::Base<unsigned int> Base_t; Base_t a(testVal); Base_t b(testVal); cout << "a=b=" << testVal << "\n"; cout << "a==b ? " << (a==b ? "TRUE" : "FALSE") << "\n"; typedef templated::Composed<unsigned int> Composed_t; Composed_t c(testVal); Composed_t d(testVal); cout << "c=d=" << testVal << "\n"; cout << "d==c ? " << (c==d ? "TRUE" : "FALSE") << "\n"; typedef templated::Outer<unsigned int>::Nested Nested_t; Nested_t e(testVal); Nested_t f(testVal); cout << "e=f=" << testVal << "\n"; cout << "e==f ? " << (e==f ? "TRUE" : "FALSE") << "\n"; // Above line causes compiler error: // error: no match for 'operator==' in 'e == f' } cout << std::endl; return 0; }

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  • Backup SQL Database Federation

    - by Herve Roggero
    One of the amazing features of Windows Azure SQL Database is the ability to create federations in order to scale your cloud databases. However until now, there were very few options available to backup federated databases. In this post I will show you how Enzo Cloud Backup can help you backup, and restore your federated database easily. You can restore federated databases in SQL Database, or even on SQL Server (as regular databases). Generally speaking, you will need to perform the following steps to backup and restore the federations of a SQL Database: Backup the federation root Backup the federation members Restore the federation root Restore the federation members These actions can be automated using: the built-in scheduler of Enzo Cloud Backup, the command-line utilities, or the .NET Cloud Backup API provided, giving you complete control on how you want to perform your backup and restore operations. Backing up federations Let’s look at the tool to backup federations. You can explore your existing federations by using the Enzo Cloud Backup application as shown below. As you can see, the federation root and the various federations available are shown in separate tabs for convenience. You would first need to backup the federation root (unless you intend to restore the federation member on a local SQL Server database and you don’t need what’s in the federation root). The steps are similar than those to backup a federation member, so let’s proceed to backing up a federation member. You can click on a specific federation member to view the database details by clicking at the tab that contains your federation member. You can see the size currently consumed and a summary of its content at the bottom of the screen. If you right-click on a specific range, you can choose to backup the federation member. This brings up a window with the details of the federation member already filled out for you, including the value of the member that is used to select the federation member. Notice that the list of Federations includes “Federation Root”, which is what you need to select to backup the federation root (you can also do that directly from the root database tab).  Once you provide at least one backup destination, you can begin the backup operation.  From this window, you can also schedule this operation as a job and perform this operation entirely in the cloud. You can also “filter” the connection, so that only the specific member value is backed up (this will backup all the global tables, and only the records for which the distribution value is the one specified). You can repeat this operation for every federation member in your federation. Restoring Federations Once backed up, you can restore your federations easily. Select the backup device using the tool, then select Restore. The following window will appear. From here you can create a new root database. You can also view the backup properties, showing you exactly which federations will be created. Under the Federations tab, you can select how the federations will be created. I chose to recreate the federations and let the tool perform all the SPLIT operations necessary to recreate the same number of federation members. Other options include to create the first federation member only, or not to create the federation members at all. Once the root database has been restored and the federation members have been created, you can restore the federation members you previously backed up. The screen below shows you how to restore a backup of a federation member into a specific federation member (the details of the federation member are provided to make it easier to identify). Conclusion This post gave you an overview on how to backup and restore federation roots and federation members. The backup operations can be setup once, then scheduled daily.

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  • LINQ-to-SQL: Could not find key member 'x' of key 'x' on type 'y'

    - by Austin Hyde
    I am trying to connect my application to a SQLite database with LINQ-to-SQL, and so far everything has worked fine. The only hitch was that the SQLite provider I am using does not support code generation (unless I was doing something wrong), so I manually coded the 4 tables in the DB. The solution builds properly, but will not run, giving me the error message Could not find key member 'ItemType_Id' of key 'ItemType_Id' on type 'Item'. The key may be wrong or the field or property on 'Item' has changed names. I have checked and double checked spellings and field names on the database and in the attribute mappings, but could not find any problems. The SQL for the table looks like this: CREATE TABLE [Items] ( [Id] integer PRIMARY KEY AUTOINCREMENT NOT NULL, [Name] text NOT NULL, [ItemType_Id] integer NOT NULL ); And my mapping code: [Table(Name="Items")] class Item { // [snip] [Column(Name = "Id", IsPrimaryKey=true, IsDbGenerated=true)] public int Id { get; set; } // [snip] [Column(Name="ItemType_Id")] public int ItemTypeId { get; set; } [Association(Storage = "_itemType", ThisKey = "ItemType_Id")] public ItemType ItemType { get { return _itemType.Entity; } set { _itemType.Entity = value; } } private EntityRef<ItemType> _itemType; // [snip] } This is really my first excursion into LINQ-to-SQL, and am learning as I go, but I cannot seem to get past this seeming simple problem. Why cannot LINQ see my association?

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  • Javascript "Member not found" error in IE8

    - by Steven
    I'm trying to debug the following block of Javascript code to see what the issue is. I'm getting an error that says "Member not found" on the line constructor = function() { in the extend:function() method. I'm not very good with Javascript, and I didn't write this, so I'm kind of lost on what the issue is. The error only occurs in IE8, it works fine in IE7 and Firefox. var Class = { create: function() { return function() { if(this.destroy) Class.registerForDestruction(this); if(this.initialize) this.initialize.apply(this, arguments); } }, extend: function(baseClassName) { constructor = function() { var i; this[baseClassName] = {} for(i in window[baseClassName].prototype) { if(!this[i]) this[i] = window[baseClassName].prototype[i]; if(typeof window[baseClassName].prototype[i] == 'function') { this[baseClassName][i] = window[baseClassName].prototype[i].bind(this); } } if(window[baseClassName].getInheritedStuff) { window[baseClassName].getInheritedStuff.apply(this); } if(this.destroy) Class.registerForDestruction(this); if(this.initialize) this.initialize.apply(this, arguments); } constructor.getInheritedStuff = function() { this[baseClassName] = {} for(i in window[baseClassName].prototype) { if(!this[i]) this[i] = window[baseClassName].prototype[i]; if(typeof window[baseClassName].prototype[i] == 'function') { this[baseClassName][i] = window[baseClassName].prototype[i].bind(this); } } if(window[baseClassName].getInheritedStuff) { window[baseClassName].getInheritedStuff.apply(this); } } return constructor; }, objectsToDestroy : [], registerForDestruction: function(obj) { if(!Class.addedDestructionLoader) { Event.observe(window, 'unload', Class.destroyAllObjects); Class.addedDestructionLoader = true; } Class.objectsToDestroy.push(obj); }, destroyAllObjects: function() { var i,item; for(i=0;item=Class.objectsToDestroy[i];i++) { if(item.destroy) item.destroy(); } Class.objectsToDestroy = null; } }

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  • Why does setting this member in C fail?

    - by Lee Crabtree
    I'm writing a Python wrapper for a C++ library, and I'm getting a really weird when trying to set a struct's field in C. If I have a struct like this: struct Thing { PyOBJECT_HEAD unsigned int val; }; And have two functions like this: static PyObject* Thing_GetBit(Thing* self, PyObject* args) { unsigned int mask; if(!PyArg_ParseTuple(args, "I", &mask) Py_RETURN_FALSE; if((self->val & mask) != 0) Py_RETURN_TRUE; Py_RETURN_FALSE; } static PyObject* Thing_SetBit(Thing* self, PyObject* args) { unsigned int mask; bool on; if(!PyArg_ParseTuple(args, "Ii", &mask, &on)) Py_RETURN_FALSE; if(on) thing->val |= mask; else thing->val &= ~mask; Py_RETURN_TRUE; } Python code that calls the first method works just fine, giving back the value of the struct member. Calls to the SetBit method give an error about an object at address foo accessing memory at address bar, which couldn't be "written". I've poked around the code, and it's like I can look at the value all I want, both from C and Python, but the instant I try to set it, it blows up in my face. Am I missing something fundamental here?

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  • error C3662: override specifier 'new' only allowed on member functions of managed classes

    - by William
    Okay, so I'm trying to override a function in a parent class, and getting some errors. here's a test case #include <iostream> using namespace std; class A{ public: int aba; void printAba(); }; class B: public A{ public: void printAba() new; }; void A::printAba(){ cout << "aba1" << endl; } void B::printAba() new{ cout << "aba2" << endl; } int main(){ A a = B(); a.printAba(); return 0; } And here's the errors I'm getting: Error 1 error C3662: 'B::printAba' : override specifier 'new' only allowed on member functions of managed classes c:\users\test\test\test.cpp 12 test Error 2 error C2723: 'B::printAba' : 'new' storage-class specifier illegal on function definition c:\users\test\test\test.cpp 19 test How the heck do I do this?

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  • Embedding Lua functions as member variables in Java

    - by Zarion
    Although the program I'm working on is in Java, answering this from a C perspective is also fine, considering that most of this is either language-agnostic, or happens on the Lua side of things. In the outline I have for the architecture of a game I'm programming, individual types of game objects within a particular class (eg: creatures, items, spells, etc.) are loaded from a data file. Most of their properties are simple data types, but I'd like a few of these members to actually contain simple scripts that define, for example, what an item does when it's used. The scripts will be extremely simple, since all fundamental game actions will be exposed through an API from Java. The Lua is simply responsible for stringing a couple of these basic functions together, and setting arguments. The question is largely about the best way to store a reference to a specific Lua function as a member of a Java class. I understand that if I store the Lua code as a string and call lua_dostring, Lua will compile the code fresh every time it's called. So the function needs to be defined somehow, and a reference to this specific function wrapped in a Java function object. One possibility that I've considered is, during the data loading process, when the loader encounters a script definition in a data file, it extracts this string, decorates the function name using the associated object's unique ID, calls lua_dostring on the string containing a full function definition, and then wraps the generated function name in a Java function object. A function declared in script run with lua_dostring should still be added to the global function table, correct? I'm just wondering if there's a better way of going about this. I admit that my knowledge of Lua at this point is rather superficial and theoretical, so it's possible that I'm overlooking something obvious.

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  • convincing C# compiler that execution will stop after a member returns

    - by Sarah Vessels
    I don't think this is currently possible or if it's even a good idea, but it's something I was thinking about just now. I use MSTest for unit testing my C# project. In one of my tests, I do the following: MyClass instance; try { instance = getValue(); } catch (MyException ex) { Assert.Fail("Caught MyException"); } instance.doStuff(); // Use of unassigned local variable 'instance' To make this code compile, I have to assign a value to instance either at its declaration or in the catch block. However, Assert.Fail will never, to the best of my knowledge, allow execution to proceed past it, hence instance will never be used without a value. Why is it then that I must assign a value to it? If I change the Assert.Fail to something like throw ex, the code compiles fine, I assume because it knows that exception will disallow execution to proceed to a point where instance would be used uninitialized. So is it a case of runtime versus compile-time knowledge about where execution will be allowed to proceed? Would it ever be reasonable for C# to have some way of saying that a member, in this case Assert.Fail, will never allow execution after it returns? Maybe that could be in the form of a method attribute. Would this be useful or an unnecessary complexity for the compiler?

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  • Call to a member function num_rows() on a non-object

    - by Patrick
    I need to get the number of rows of a query (so I can paginate results). As I'm learning codeigniter (and OO php) I wanted to try and chain a -num_rows() to the query, but it doesn't work: //this works: $data['count'] = count($this->events->findEvents($data['date'], $data['keyword'])); //the following doesn't work and generates // Fatal Error: Call to a member function num_rows() on a non-object $data['count2'] = $this->events->findEvents($data['date'], $data['keyword'])->num_rows(); the model returns an array of objects, and I think this is the reason why I can't use a method on it. function findEvents($date, $keyword, $limit = NULL, $offset = NULL) { $data = array(); $this->db->select('events.*, venues.*, events.venue AS venue_id'); $this->db->join('venues', 'events.venue = venues.id'); if ($date) { $this->db->where('date', $date); } if ($keyword) { $this->db->like('events.description', $keyword); $this->db->or_like('venues.description', $keyword); $this->db->or_like('band', $keyword); $this->db->or_like('venues.venue', $keyword); $this->db->or_like('genre', $keyword); } $this->db->order_by('date', 'DESC'); $this->db->order_by('events.priority', 'DESC'); $this->db->limit($limit, $offset); //for pagination purposes $Q = $this->db->get('events'); if ($Q->num_rows() > 0) { foreach ($Q->result() as $row) { $data[] = $row; } } $Q->free_result(); return $data; } Is there anything that i can do to be able to use it? EG, instead of $data[] = $row; I should use another (OO) syntax?

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