C++ pass function as paramenter

void retrieveTime5(char *dtValue);
void showTime6();
void passFunc(void(*funcName)());

int main()
{
    passFunc(&showTime6);
    return 0;
}

void passFunc(void(*funcName)())
{
    chrono::time_point<chrono::system_clock> startTime;
    chrono::time_point<chrono::system_clock> endTime;
    startTime=chrono::system_clock::now();
    printf("Started in passFunc!\n");
    (*funcName)();
    endTime=chrono::system_clock::now();
    printf("Ended in passFunc!\n");
    cout<<"Time cost:"
    <<chrono::duration_cast<chrono::seconds>(endTime-startTime).count()<<" seconds,"
    <<chrono::duration_cast<chrono::milliseconds>(endTime-startTime).count()<<" milliseconds,"
    <<chrono::duration_cast<chrono::microseconds>(endTime-startTime).count()<<" microseconds,"
    <<chrono::duration_cast<chrono::nanoseconds>(endTime-startTime).count()<<" nanoseconds."<<endl;
}

void showTime6()
{
    char *dtValue=(char*)malloc(20);
    for(int i=0;i<10;i++)
    {
        retrieveTime5(dtValue);
        printf("Index=%d,value=%s\n",i,dtValue);
        sleep(1);
    }
    free(dtValue);
}

void retrieveTime5(char *dtValue)
{
    time_t rawTime = time(NULL);
    struct tm tmInfo = *localtime(&rawTime);
    strftime(dtValue, 20, "%Y%m%d%H%M%S", &tmInfo);
}

Declare

void passFunc(void(*funcName)());

Implement

void passFunc(void(*funcName)())
{ 
    (*funcName)(); 
}

Invoke

int main()
{
    passFunc(&showTime6);
    return 0;
}

 

When the function with parameters,declare as below.

void callFunc6(void (*funcName)(char *));

Implementation

#include <uuid/uuid.h>

void callFunc6(void (*funcName)(char *))
{
    char *uuidValue = (char *)malloc(40);
    (*funcName)(uuidValue);
    printf("UuidValue=%s\n", uuidValue);
    free(uuidValue);
}

void retrieveUuid1(char *uuidValue)
{
    uuid_t newUUID;
    uuid_generate(newUUID);
    uuid_unparse(newUUID, uuidValue);
}

Invoke the function

int main()
{
    call7();
    return 0;
}

void call7()
{
    callFunc6(&(retrieveUuid1));
}

Compile

g++ -g -std=c++2a -I. UtilityHelper.cpp h1.cpp -o h1 -luuid

 

 

The compact version as below.

void funcCall8(void(*funcName)());
void callFunc9();
void printNum();

int main()
{
    callFunc9();
    return 0;
}

void callFunc9()
{ 
    funcCall8(&printNum);
}

void printNum()
{
    for(int i=0;i<10;i++)
    {
        printf("Num=%d\n",i);
        sleep(1);
    }
}

void funcCall8(void(*funcName)())
{
    (*funcName)();
}