vector内数据的深拷贝和浅拷贝

来源：互联网发布：win7 查看端口占用编辑：程序博客网时间：2024/06/13 20:57

结论：vector内数据使用结构体的话是深拷贝，vector内的数据会拷贝一份保存，vector内数据不会丢失。如果vector内数据是指针的话是进行浅拷贝，数据超出作用域后会自动析构，vector内所指向的数据会被更改和丢失，所以vector如果作为全局变量，不应该使用指针。

#include <iostream>#include <vector>#include <map>#include <string>using namespace std;struct OtherDevice{map<string,string> datas;};vector<OtherDevice> otherDevices;//全局变量  vector内数据进行值得深拷贝 如果是指针的话进行浅拷贝，数据超出作用域后会自动析构，所以vector如果作为全局变量，不应该使用指针。//otherDevices能够保存数据int main( int argc, char* argv[] ){for (int j=0;j<10;j++){char buffer[1024];sprintf(buffer,"hehe_%d",j);OtherDevice tmpDevice;tmpDevice.datas.insert(std::pair<std::string,std::string>("device_id",string(buffer)));otherDevices.push_back(tmpDevice);}//tmpDevice.datas.clear(); 不能清空，否则全局变量otherDevices数据丢失printf("otherDevices.size=%d ",otherDevices.size());if(otherDevices.size()>0){printf("otherDevices.datas.size=%d ",otherDevices.at(0).datas.size());}else{printf("otherDevices.datas.size=0 ");}otherDevices.clear();return 0;}

#include <iostream>#include <vector>#include <map>#include <string>using namespace std;vector<map<string,string>> otherDevices;//全局变量  vector内数据进行值得深拷贝 如果是指针的话进行浅拷贝，数据超出作用域后会自动析构，所以vector如果作为全局变量，不应该使用指针。//otherDevices能够保存全局数据int main( int argc, char* argv[] ){for (int j=0;j<10;j++){char buffer[1024];sprintf(buffer,"hehe_%d",j);map<string,string> datas;datas.insert(std::pair<std::string,std::string>("device_id",string(buffer)));otherDevices.push_back(datas);}printf("otherDevices.size=%d ",otherDevices.size());if(otherDevices.size()>0){printf("otherDevices.datas.size=%d ",otherDevices.at(0).size());}else{printf("otherDevices.datas.size=0 ");}otherDevices.clear();return 0;}

#include <iostream>#include <vector>#include <map>#include <string>using namespace std;struct OtherDevice{map<string,string> datas;};static vector<OtherDevice*> otherDevices;//static全局变量  防止vector内数据超过作用域自动析构//otherDevices不能够保存数据int main( int argc, char* argv[] ){for (int j=0;j<10;j++){char buffer[1024];sprintf(buffer,"hehe_%d",j);OtherDevice tmpDevice;tmpDevice.datas.insert(std::pair<std::string,std::string>("device_id",string(buffer)));otherDevices.push_back(&tmpDevice);}//tmpDevice.datas.clear(); 不能清空，否则全局变量otherDevices数据丢失printf("otherDevices.size=%d ",otherDevices.size());if(otherDevices.size()>0){printf("otherDevices.datas.size=%d ",otherDevices.at(0)->datas.size());}else{printf("otherDevices.datas.size=0 ");}otherDevices.clear();return 0;}

#include <iostream>#include <vector>#include <map>#include <string>using namespace std;vector<map<string,string>*> otherDevices;//otherDevices不能够保存数据int main( int argc, char* argv[] ){for (int j=0;j<10;j++){char buffer[1024];sprintf(buffer,"hehe_%d",j);map<string,string> datas;datas.insert(std::pair<std::string,std::string>("device_id",string(buffer)));otherDevices.push_back(&datas);}printf("otherDevices.size=%d ",otherDevices.size());if(otherDevices.size()>0){printf("otherDevices.datas.size=%d ",otherDevices.at(0)->size());}else{printf("otherDevices.datas.size=0 ");}otherDevices.clear();return 0;}

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