我aStudent destroyStudent()函数中的指针aStudent，然后我将nullptr设置为aStudent。但是，在运行该功能后，nullptr不再设置为nullptr，因此我必须再次将其设置为#include <cstring>
using namespace std;
struct Student {
char * name;
float gpa;
};
Student * createStudent(const char name[], float gpa) {
struct Student * student = new Student;
student->name = (char*)malloc(strlen(name + 1)); //allocate only enough memory to fit the given name
strcpy(student->name, name);
student->gpa = gpa;
return student;
}
bool destroyStudent(Student * aStudent) {
if(aStudent) { //check whether this pointer is already null.
free(aStudent->name);
delete aStudent; // ******This is where the issue is******
aStudent = nullptr;
return true;
}
return false; //aStudent is already null
}
int main() {
Student * student1 = createStudent("Charles", 2.5);
cout << student1->name << " and " << student1->gpa << endl;
destroyStudent(student1);
if(student1) {
cout << "Pointer is NOT null!!!" << endl;
student1 = nullptr;
}
if(!student1) {
cout << "The pointer is null now." << endl;
}
return 0;
}
。
import Foundation
class RecordedAudio: NSObject{
var filePathUrl: NSURL!
var title: String!
}
答案 0 :(得分：6)
问题是aStudent是指针的本地副本。
您需要通过引用传递中的指针，如下所示：
bool destroyStudent(Student*& aStudent) {
if(aStudent) { //check whether this pointer is already null.
free(aStudent->name);
delete aStudent; // ******This is where the issue is******
aStudent = nullptr;
return true;
}
return false; //aStudent is already null
}
这样就是你改变的外部指针，而不是本地副本。
答案 1 :(得分：0)
C ++使用pass-by-value。
您要将destroyStudent()方法的本地变量设置为nullptr，而不是main()中的变量。