I have the following code:
#interface Model ()
{
//...
std::function<bool(CGFloat, CGFloat)> greaterThan;
std::function<bool(CGFloat, CGFloat)> lesserThan;
//...
}
#end
Everything worked fine in my original project.
I just created a new project, and dragged and dropped the files between the two, and in the new project I have the following errors for the above two lines:
No type named 'function' in namespace 'std'
I don't know what the problem is - The files are .mm , why can't it find function in the names space std ?
Add #include <functional> to the top of your code.
Also remember to use -std=c++0x (or equivalent) in your compiler parameters; this will enable C++11 standard which is required for std::function.
Related
So in my Visual Studio solution I'm making a library and I have two Visual Studio projects, one for the library and one for the sandbox. In the library I'm trying to use forward declarations to create a class. What I'm simply doing in this example is creating a header file for my class, declaring std::string with the following forward declaration and creating a member pointer with that class.
Library project:
ClassFromLibrary.h
#pragma once
namespace std {
class string;
}
class ClassFromLibrary {
public:
ClassFromLibrary();
~ClassFromLibrary();
std::string* forwardDeclaredString;
};
ClassFromLibrary.cpp
#include "ClassFromLibrary.h"
#include <string>
ClassFromLibrary::ClassFromLibrary()
: forwardDeclaredString(new std::string("Hello, world!"))
{
}
ClassFromLibrary::~ClassFromLibrary()
{
}
Sandbox project
main.cpp
#include <Library/ClassFromLibrary.h>
#include <iostream>
int main()
{
ClassFromLibrary test;
std::cout <<
*test.forwardDeclaredString //Root of the problem
<< std::endl;
std::cin.get();
}
The problem
As I said earlier, the library project compiles perfectly. However, the error which I mentioned in the title shows up when the forward declared member variable is referenced in any file from the sandbox project. I have a larger project where I get the same error, and the reason I want to achieve this is because I am using other external libraries within my library project, and when I create applications with it I don't want to have to put all the library include directories in the project properties, only the one for my library.
Thanks in advance!
You know that putting names in namespace std makes program ill-formed (except for some cases?)? Well, know you know why. The bug you have is a symptom of undefined behavior.
In my test, the way you declared your forward declaration in std is not how it is actually declared in string header. Yet it's a same name, so now you have name conflict (you have it as soon as you include iostream, which includes string. This is what my compiler is telling me when I am try compile your code:
/opt/compiler-explorer/gcc-8.2.0/lib/gcc/x86_64-linux-gnu/8.2.0/../../../../include/c++/8.2.0/bits/basic_string.h:6628:17:
error: reference to 'string' is ambiguous
struct hash<string>
This is different from the error you put in the question, but since the behavior is undefined, anything can happen.
I just tried to compile my C++ code and an error appears when I try to do so.
The error appears on line 9
Here are the versions of the gcc and g++ and such
Any help would be appreciated.
Edit:
I am also including Movie.h:
And also Movie.cpp:
https://puu.sh/vb53G/9e9abd1832.png (I was not able to include more than 3 images due to restrictions)
Firstly, in your Movie.h file, you have not included the string header file correctly. It should be:
#include <string> // without the .h extension
error: 'string' does not name a type
Secondly, you have forgotten to add the closing parenthesis of the constructor function of class "Movie". I am assuming that you have added this now, after the edit
As for the marking done by your compiler, you may find the following StackOverflow post helpful:
StackOverflow Post: Unresolved inclusion iostream.
The link is for the Eclipse IDE, but you can find a similar solution for your own IDE (I cannot tell which one you have).
The line under the #include is just a warning (I'm not sure why).
However, the errors are from the "Movie" class:
1. add "using namespace std" on the top of this class.
2. close the parenthesis on the constructor of 'Movie'.
The error messages are fairly clear:
'string' does not name a type
That is, the compiler is unaware of the type string because either:
you have not #include <string> in Movie.h
or you have, but have not brought it into your namespace with a using namespace std;
although why not just refer to it as std::string?
You are missing
#include <string>
I know, it may seem strange, but my goal is to undefine a class in C++. The root of the problem is in combining TinyXML2 and Boost unit tests.
Contents of the header file (Configuration.h) which is being tested:
...
#include <tinyxml2.h>
...
And this is the contents of my configurationTests.h file:
#include "unitTests.h"
#include "Configuration.h"
BOOST_AUTO_TEST_SUITE(configuration_test)
BOOST_AUTO_TEST_CASE(basic) {
...
}
BOOST_AUTO_TEST_SUITE_END( )
When I try to compile my tests, I'm getting an error:
error C2371: 'XMLDocument' : redefinition; different basic
types c:\program files (x86)\windows kits\8.0\include\um\msxml.h 10085
Inside this file (msxml.h) on line 10085 we have this class definition:
class DECLSPEC_UUID("CFC399AF-D876-11d0-9C10-00C04FC99C8E")
XMLDocument;
When I remove those two lines, my tests do compile and everything seems fine. Of course, this is not a solution, but that fact prooves that something inside Boost unit tests library includes msxml.h and somehow leads to conflict with TinyXML2 library.
I tried different solutions found in Google (like writing "#define WIN32_LEAN_AND_MEAN"), removing "using namespace tinyxml2" and making changes inside tinyxml2.cpp - nothing actually helps.
So, my question is simple: can I undefine (unload?) previously defined class in compile time in some tricky way? I tried "#undef XMLDocument", "#define XMLDocument 1" + "#undef XMLDocument" - nothing works.
Update: Actually, I kinda solved the problem by writing "#define MSXML_LIBRARY_DEFINED" on the first line of configurationTests.h. But still, I would love to know an answer to this topic question.
I think you have used default namespace for tinyxml2.
Try to delete using namespace tinyxml2 and then use it like in this example:
tinyxml2::XMLDocument xDoc;
try this:
namespace your_name_space
{
#include <tinyxml2.h>
}
From now all classes inside the tinyxml2 are hidden by your namespace.
The namespece must be declared also for the tinyxml2.cpp file.
I'm new to C++ and in my Intro to programming design and concepts class we're now on graphics. I've been able to make programs with just FLTK's library but we have to use Bjarne's library such as GUI.h, Graph.h, Simple_window.h, Point.h. A simple program like a simple window program won't compile and gives a usual response of:
Simple_window.h:17: error: reference to ‘Window’ is ambiguous
I have also tried compiling using:
fltk-config --compile main.cpp
This yields the same results.
I have tried running the make file that Bjarne has provided with in the folder but that always comes up with errors and makes no .o files.
Note: I have also tried compiling on mac OSX and Ubuntu.
I never used either of those libraries, but I saw that tutorials for FLTK always begin with using namespace fltk; statement, which imports all FLTK classes, including fltk::Window to the root namespace.
The library by B. Stroustrup is contained in namespace called Graph_lib and it also has a class called Window.
Now, the file Simple_window.h has using namespace Graph_lib; statement at the beginning, which imports Graph_lib::Window to the root namespace. And this is where the ambiguity is coming from.
So I would suggest to omit the using statement (at least from using namespace fltk) and to use FLTK classes with full specification (e.g. fltk::Window instead of just Window). This should solve the ambiguity.
As a side note, this is nice example, why having using namespace at file level in a header file is a bad idea.
References:
http://www.fltk.org/doc-2.0/html/index.html
http://www.stroustrup.com/Programming/Graphics/Simple_window.h
EDIT: I tried to compile the library containing Simple_window myself and, at least under linux, it the ambiguity seems to be between class Graph_lib::Window from the library and typedef Window from xlib as well. xlib is C library and you can't really do anything about it, so you will have to get rid of using namespace Graph_lib in Stroustup's library.
In the file Simple_window.h:
delete using namespace Graph_lib;
change Window to Graph_lib::Window
Button to Graph_lib::Button
and Address to Graph_lib::Address
Then in the file Simple_window.cpp:
change Address to Graph_lib::Address again
and reference_to<Simple_window> to Graph_lib::reference_to<Simple_window>
Then it should compile. If you have different version than the one that's on stroustrup.com, you may need to fully qualify (add Graph_lib::) more classes.
I just had the same kind of problems (unresolved external symbols) using Simple_window.h and trying to compile a the following peace of code:
int main(){
// create a reference point for the window
Point topLeft(50,50);
// initialize a Simple_window object to size: 600x400 pixels, labeled: My window
Simple_window myWindow(topLeft, 600, 400, "My window");
// pass control to GUI
myWindow.wait_for_button();
return 0;
}
The solution was to add to the project (along with the main.cpp) all the respective .cpp files of the included .h files:("Graph.h", "Window.h", "Simple_window.h", "GUI.h")
I'm trying to use C++ code in my ios app (I really don't like objective C, I'm going to use it only when necessary [view control, etc]) and while everything seems to be working I get an error in the following test file.
#ifndef prueba3_GlobalStatic_h
#define prueba3_GlobalStatic_h
#include <string>
using namespace std;
class GlobalStatic
{
public:
GlobalStatic();
~GlobalStatic();
string foo();
private:
int integerValue;
};
#endif
When I try to build the project the IDE gives me the following error:
" 'string' file not found"
I've looked around but cannot find a conclusive answer; any help would be appreciated. In essence, how do I get the standard library working?
One cause of missing c++ headers is including them from an objective-c context as opposed to from objective-c++ -- and you can't use the c++ stl from c! The easier solution is to simply change all your .m files to .mm, .mm will send them to the objective-c++ compiler.