Question

我对此感到非常沮丧。我阅读了大多数stackoverflow注释和示例，但都没有显示出任何作用。我刚开始做c ++。

我希望代码打印“ Hello World”。

这是我的代码示例（我可以提供完整的代码，但由于其中有很多代码，因此我将不再需要）：

#include <iostream>
#include <thread>

using namespace std;

class Greeting {
    public:
        void hi() {
           cout << "Hello World!\n";
        }
};

int main() {

Greeting g;

thread t(g.hi);
t.join();

return 0;
}

错误：

||=== Build: Debug in Cookie Island (compiler: GNU GCC Compiler) ===|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
||In instantiation of 'struct std::_Bind_check_arity<void (Greeting::*)()>':|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
|1538|required from 'struct std::_Bind_simple_helper<void (Greeting::*)()>'|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
|1552|  required by substitution of 'template<class _Callable, class ... _Args> 
typename std::_Bind_simple_helper<_Func, _BoundArgs>::__type 
std::__bind_simple(_Callable&&, _Args&& ...) 
[with _Callable = void (Greeting::*)(); _Args = {}]'|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\thread
|142|required from 'std::thread::thread(_Callable&&, _Args&& ...) 
[with _Callable = void (Greeting::*)(); _Args = {}]'|
C:\Users\Andrew Shen\Desktop\Cookie Island\main.cpp|51|required from here|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
|1426|error: static assertion failed: Wrong number of arguments for pointer-to-member|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
||In instantiation of 'struct std::_Bind_simple<std::_Mem_fn<void (Greeting::*)()>()>':|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\thread
|142|required from 'std::thread::thread(_Callable&&, _Args&& ...) 
[with _Callable = void (Greeting::*)(); _Args = {}]'|
C:\Users\Andrew Shen\Desktop\Cookie Island\main.cpp|51|required from here|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
|1505|error: no type named 'type' in 'class std::result_of<std::_Mem_fn<void (Greeting::*)()>()>'|
C:\Program Files (x86)\CodeBlocks\MinGW\lib\gcc\mingw32\5.1.0\include\c++\functional
|1526|error: no type named 'type' in 'class std::result_of<std::_Mem_fn<void (Greeting::*)()>()>'|
||=== Build failed: 4 error(s), 7 warning(s) (0 minute(s), 1 second(s)) ===|

更新：这更像是我的代码。

#include <iostream>
#include <thread>
#include <string>

using namespace std;

class Greeting {
    public:
        void hi(string txt) {
           cout << "Hello World!"+txt << endl;
        }
};

int main() {
string t = " More...";

Greeting g;

thread t(g.hi, &g, t);
t.join();

return 0;
}

Blockquote || ===构建：在Cookie Island中进行调试（编译器：GNU GCC编译器）=== | C：\ Program Files（x86）\ CodeBlocks \ MinGW \ lib \ gcc \ mingw32 \ 5.1.0 \ include \ c ++ \ functional ||实例化为'struct std :: _ Bind_simple）>（Greeting *，std :: __ cxx11：：basic_string *）>'：| C：\ Program Files（x86）\ CodeBlocks \ MinGW \ lib \ gcc \ mingw32 \ 5.1.0 \ include \ c ++ \ thread | 142 |从'std :: thread :: thread（_Callable &&，_Args && ...）[与_Callable = void（Greeting :: ）（std :: __ cxx11 :: basic_string）; _Args = {问候，std :: __ cxx11 :: basic_string，std :: allocator> *}]'| C：\ Users \ Andrew Shen \ Desktop \ Cookie Island \ main.cpp | 52 |从此处要求| C：\ Program Files（x86）\ CodeBlocks \ MinGW \ lib \ gcc \ mingw32 \ 5.1.0 \ include \ c ++ \ functional | 1505 |错误：'class std :: result_of）中没有名为'type'的类型> *，std :: __ cxx11 :: basic_string *）>'| C：\ Program Files（x86）\ CodeBlocks \ MinGW \ lib \ gcc \ mingw32 \ 5.1.0 \ include \ c ++ \ functional | 1526 |错误：'class std :: result_of）中没有名为'type'的类型> *，std :: __ cxx11 :: basic_string *）>'| || ===构建失败：2个错误，3个警告（0分钟，1秒）=== |

Answer 1

成员函数不是对象的一部分，而是类。您需要完整的限定功能名称。您需要执行以下操作：

thread t(&Greeting::hi, &g, str);

此外，您不小心将't'用作凝视变量的名称以及该线程的名称，我将其修改为字符串的str。

Answer 2

以下任何作品，

string str = " More...";

thread t(Greeting::hi, g, str);

或

thread t(&Greeting::hi, g, str);

或

thread t(Greeting::hi, &g, str);

或

thread t(&Greeting::hi, &g, str);

能否请您解释所有这些情况之间的区别。 @Abhinav

C ++线程类不起作用，并给出功能和线程文件错误

2 个答案: