I am new to c++, trying to debug the following line of code
class cGameError
{
string m_errorText;
public:
cGameError( char *errorText )
{
DP1("***\n*** [ERROR] cGameError thrown! text: [%s]\n***\n",
errorText );
m_errorText = string( errorText );
}
const char *GetText()
{
return m_errorText.c_str();
}
};
enum eResult
{
resAllGood = 0, // function passed with flying colors
resFalse = 1, // function worked and returns 'false'
resFailed = –1, // function failed miserably
resNotImpl = –2, // function has not been implemented
resForceDWord = 0x7FFFFFFF
};
This header file is included in the program as followed
#include "string.h"
#include "stdafx.h"
#include "Chapter 01 MyVersion.h"
#include "cGameError.h"
You need to include <string>, not "string.h". Or in addition to "string.h".
string.h is the C header for the standard C string handling functions (strcpy() and friends.)
<string> is the standard C++ header where 'string' is defined.
You also need to specify the std namespace when using string:
std::string m_errorText;
Or by using:
using namespace std;
Somewhere at the top of your file.
You should also use angle brackets for system include files.
You've provided little enough information that this is only a wild guess, but at first glance, I'd guess the problem is that you haven't included <string>, only "string.h" (the former defines the C++ std::string class, the latter the C functions for manipulating nul-terminated strings.
As an aside, you normally want to use angle-brackets for system headers, so it should be <string.h>.
Try #include <string>, instead of #include "string.h", string.h/cstring is the old C-string header, string is the new C++ std::string class header. And you normally use angle-brackets for system headers.
Related
How come when I do
using std::string;
I get an error but after I include string, it doesn't throw error. Same with std::setprecision.
#include <string>
using std::string; //Throws error when string library not included
#include <iomanip>
using std::setprecsion; //Throw error when iomanip library not included
int main()
{
//stuff
}
When I leave out the #include preprocessor, why does it throw an error saying string or setprecision is not part of std namespace, but when I add the libraries they don't? Do they somehow get added to std namespace after including the libraries?
Would it kind of be like bracket notation in JavaScript?
var obj = {
one: 1
};
obj['two'] = 2;
It is simply because the functions you are trying to use are defined in their library files. In C , C++ you have to write #include to include the library in your program and use its functions.
I was splitting up my program into a header and implementation file per usual, however, when I tried to run the code, I got a ton of compile errors. This seems to be an issue with my computer or IDE, but I have not seen it before. This should be relatively simple as it is for a class project.
The code is as follows:
colorPicker.h
#pragma once
class colorPicker {
private:
string colorArray[7];
public:
colorPicker();
void printAllColors();
string randomColor();
};
colorPicker.cpp
#include "colorPicker.h"
#include "stdafx.h"
#include <iostream>
#include <string>
#include <ctime>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
colorPicker::colorPicker() {
colorArray[0] = "Red";
colorArray[1] = "Green";
colorArray[2] = "Purple";
colorArray[3] = "Yellow";
colorArray[4] = "Orange";
colorArray[5] = "Indigo";
colorArray[6] = "Pink";
}
void colorPicker::printAllColors() {
for (int i = 0; i < 7; i++) {
cout << colorArray[i] << endl;
}
}
string colorPicker::randomColor() {
srand((unsigned)time(0));
int j = 0;
j = rand() % 7;
return colorArray[j];
}
main.cpp
#include "colorPicker.h"
#include "stdafx.h"
#include <iostream>
#include <string>
#include <ctime>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
int main() {
colorPicker p;
p.printAllColors();
cout << "Random Color: " << p.randomColor() << endl;
system("pause");
return 0;
}
There are 20 errors given by the compiler, however, they all seem to be stemming from two undeclared identifiers which are most definitely declared. I am at a loss for what I could possibly do to fix it, and this project is due Sunday. Thank you.
Here are the errors
Tons of Errors
You need #include "colorPicker.h" in colorPicker.cpp. Each .cpp file is handled basically independently by the compiler and they are all joined at the end by the "linker." When the compiler looks at colorPicker.cpp without an include of the corresponding header, it's at a loss as to the definition of all the classes you're working with.
There are a few things you are doing wrong. I'll just pick on a couple.
Firstly, each header file you write should be self-contained - in the sense that, if it relies on content of some other headers, it includes that header. If a compilation unit (a formal name for a source file with a .cpp in your case) includes your header, it should not have to include something else your header depends on.
Second, it is a bad idea for a header to rely on any using directive, such as using namespace std. There are plenty of explanations of that available, so I won't repeat.
To understand the above, look at colorPicker.h
class colorPicker {
private:
string colorArray[7];
public:
colorPicker();
void printAllColors();
string randomColor();
};
Firstly, this depends on string, but there is no definition of string visible in the header file. Usage of that type depends on the standard header <string>.
Second, that string type is within namespace std. So your header relies on the compilation unit (the source file that includes your header) having previously used a using directive i.e. using namespace std.
To fix these two problems, change the header to
#ifndef SOME_MACRO_UNIQUE_TO_YOUR_COLOR_PICKER_HEADER
#define SOME_MACRO_UNIQUE_TO_YOUR_COLOR_PICKER_HEADER
#include <string>
class colorPicker
{
private:
std::string colorArray[7];
public:
colorPicker();
void printAllColors();
std::string randomColor();
};
#endif
(I've also done some minor changes of layout, since I have various reasons to prefer that.
However, the #include <string> means that this version will not fail to compile, as yours does, if it is included by a compilation unit that does not have #include <string>.
The usage of the fully qualified name std::string, rather than string, also means there is no dependence on the using directive using namespace std. It also means compilation errors can't be triggered in your header if your compilation unit has another using directive.
I've also used an include guard, rather than #pragma once. Although most modern compilers support #pragma once, it is actually not standard C++ (a #pragma, by definition in the standard, is a compiler-specific hook). Include guards are supported in standard C++.
If you've done that, your code should mostly compile as is. However, optionally, you may wish to
remove the using directives using namespace std from your other files. If you do that, you will need to change the definition of colorPicker::randomColor() in colorPicker.cpp so it returns the fully qualified type std::string rather than string.
Remove #include <string> from files that have #include "colorPicker.h". This is possible, since colorPicker.h now includes <string>. This step is optional, since there is no problem with including standard headers more than once in a compilation unit.
A few other notes
In C++, although it is not a major concern, it is usually considered better to use include <cstdio> and <cstdlib> rather than the C headers <stdio.h> and <stdlib.h>.
Your code is calling srand((unsigned)time(0)) whenever colorPicker::randomColor() is called. It is better to only call it once in an entire program, not in a function that may be called multiple times.
A header file should be self-contained as far as #includes go. That means that you should be able to #include the header file without having to include other stuff before it!
Your colorPicker.h does not meet that requirement. It apparently uses std::string from the standard library but does not have an #include <string> on top, so everyone who uses colorPicker.h has to remember to put an #include <string> before it. That's pretty annoying.
Even worse, colorPicker.h refers to std::string as string, which implies a using std::string; or using namespace std; somewhere before any #include "colorPicker.h" line, and both of those are very bad coding style in C++, if not used in tighter scopes.
Here's how to fix the header file:
#pragma once
#include <string>
class colorPicker {
private:
std::string colorArray[7];
public:
colorPicker();
void printAllColors();
std::string randomColor();
};
As far as your *.cpp files go, I can see that you are using #include "stdafx.h". Why? It's a non-standard Microsoft thing completely unnecessary in your case. You are also using it incorrectly. It must be the first include. Just remove it entirely.
Some other suggested cleanup:
using namespace std; lines in *.cpp files is not as bad as in header files, but if I were you, I'd just get rid of it completely. Just use complete names. Say std::cout, not cout. And so on. It's just the most consistent way and it avoids a lot of trouble.
You include a lot of headers which you don't need. For example, what's <ctime> for?
Don't use system("pause");. Do not look for artificial ways of pausing a command-line program.
You may need add head file and in colorPicker.h.
And the std namespace is needed while using string.
BTW, the header guards is recommended strongly.
#ifndef COLOR_PICKER_H
#define COLOR_PICKER_H
#pragma once
#include <string>
class colorPicker {
private:
std::string colorArray[7];
public:
colorPicker();
void printAllColors();
std::string randomColor();
};
#endif
I can't declare a string in my program:
string MessageBoxText = CharNameTextBox->Text;
it just doesn't work. It says string is undeclared identifier. What am I missing in the namespace or include or something like that?
Make sure you've included this header:
#include <string>
And then use std::string instead of string. It is because string is defined in std namespace.
And don't write this at namespace scope:
using namespace std; //bad practice if you write this at namespace scope
However, writing it at function scope is not that bad. But the best is one which I suggested before:
Use std::string as:
std::string MessageBoxText = CharNameTextBox->Text;
To use the standard string class in C++ you need to #include <string>. Once you've added the #include directive string will be defined in the std namespace and you can refer to it as std::string.
E.g.
#include <string>
#include <iostream>
int main()
{
std::string hw( "Hello, world!\n" );
std::cout << hw;
return 0;
}
Are you by any way compiling using C++/CLI, the Microsoft extension for .NET, and not standard ISO C++?
In that case you should do the following:
System::String^ MessageBoxText = CharNameTextBox->Text;
Also see the following articles:
How to: Convert Between Various String Types
How to: Convert System::String to Standard String
How to: Convert Standard String to System::String
I was doing a project for computer course on programming concepts. This project was to be completed in C++ using Object Oriented designs we learned throughout the course. Anyhow, I have two files symboltable.h and symboltable.cpp. I want to use a map as the data structure so I define it in the private section of the header file. I #include <map> in the cpp file before I #include "symboltable.h".
I get several errors from the compiler (MS VS 2008 Pro) when I go to debug/run the program the first of which is:
Error 1 error C2146: syntax error : missing ';' before identifier 'table' c:\users\jsmith\documents\visual studio 2008\projects\project2\project2\symboltable.h 22 Project2
To fix this I had to #include <map> in the header file, which to me seems strange.
Here are the relevant code files:
// symboltable.h
#include <map>
class SymbolTable {
public:
SymbolTable() {}
void insert(string variable, double value);
double lookUp(string variable);
void init(); // Added as part of the spec given in the conference area.
private:
map<string, double> table; // Our container for variables and their values.
};
and
// symboltable.cpp
#include <map>
#include <string>
#include <iostream>
using namespace std;
#include "symboltable.h"
void SymbolTable::insert(string variable, double value) {
table[variable] = value; // Creates a new map entry, if variable name already exist it overwrites last value.
}
double SymbolTable::lookUp(string variable) {
if(table.find(variable) == table.end()) // Search for the variable, find() returns a position, if thats the end then we didnt find it.
throw exception("Error: Uninitialized variable");
else
return table[variable];
}
void SymbolTable::init() {
table.clear(); // Clears the map, removes all elements.
}
My guess is that you have another file that includes the header file #include "symboltable.h". And that other source file doesn't #include <map> nor #include <string> nor has using namespace std before it includes "symboltable.h".
Check which file is being compiled when you get the error. Is it maybe a different source file than the .cpp that you mentioned? Possibly something like main.cpp?
Another way to solve your problem is to put the includes you need in your header file and use std::map instead of simply map. Also you use string which is also inside the namespace std. So that needs to be std::string. And put the missing #include <string>.
Yes, you indeed have to #include <map> in the header file.
You use map in the declaration of the class, so the compiler needs to know what this map refers to. Since the definition of it is in <map> you need to include that header before using the map template class.
You could also instead #include <map> in every source file before the #include "symboltable.h" line, but usually you would just include these kind of prerequisites in the header.
Friends
On HP-UX box when Iam passing a string object to function
Im getting the following below error
Error 422: "../header/Handler.h", line 24 # 'string' is used as a type, but has not been
defined as a type. Perhaps you meant 'String' as in class String
["/opt/aCC/include/SC/String.h", line 66].
int populateBindingHandle(rpc_if_handle_t p_if_spec, string p_cell_name);
why would I get an error to use String.h not
how does a declaration String newstr;
different from
string newstr; ??
Many Thanks
Looks like there is a String class in the header mentioned by the compiler. The compiler thinks you made a typo.
If you want to use STL strings use the following:
#include <string>
int populateBindingHandle(rpc_if_handle_t p_if_spec, std::string ...)
or have a using declaration somewhere:
using std::string;
int populateBindingHandle(rpc_if_handle_t p_if_spec, std::string ...)
Note, the old-style headers have been deprecated, i.e. you should no longer use #include <string.h>