How do I initialize the value of std::shared_ptr<std::vector<std::vector<>>>?

In the following cases, how do I write the initial value (2*2 array, value 1) for data?

structure name {
    intx;
    inty;
}    

std::shared_ptr<std::vector<std::vector<std;structure name>>>data;

I tried the following, but the value was not printed because the array size was 0.

for(const auto&data:*data){
    for(const auto&data_info:data){
    data_info.x = 1;
    data_info.y = 1;
    }
}

*Additional information

#include<bits/stdc++.h>

structureSomeData{
    intx;
    inty;
    SomeData():
        x(0),
        y(0){}
    SomeData(int_num1, int_num2):
        x(_num1),
        y(_num2){}
};

struct Data {
    std::shared_ptr<std::vector<std::vector<SomeData>>>data;//☆
};

void func(const Data&data_info)
{
    auto data=std::make_shared<std::vector<std::vector<SomeData>>();
    data->push_back({{1,1},{1,1}});
　　　　　　　　data->push_back({{1,1},{1,1}});
    
　　　　　　　　for(const auto&data:*data){
        for(const auto&data_info:data){
            std::cout<<"x:"<<data_info.x<<std::endl;
            std::cout<<"y:"<<data_info.y<<std::endl;
        }
    }
}

int main (const Data & data_info)
{
    func(data_info);

    return 0;
}

output results:

 x:1
y:1
x:1
y:1
x:1
y:1
x:1
y:1

c++

2022-12-21 17:57

2 Answers

In this case, how should I write the initial value (2*2 array, value 1) for data?

Note This is an example of not using initializer_list

using T=std::vector<SomeData>;;
std::shared_ptr<std::vector<T>>data=std::make_shared<std::vector<T>>(2,T(2,SomeData(1,1));

This is an example of when you want to set the initial value later instead of initializing.

using T=std::vector<SomeData>;;
std::shared_ptr<std::vector<T>>data;

std::shared_ptr<std::vector<T>>tmp=std::make_shared<std::vector<T>>(2,T(2,SomeData(1,1));
data.swap(tmp)

2022-12-22 01:26

If you want to do everything with initialization:

using T=std::vector<Structure Name >;;
auto data=std::make_shared<std::vector<T>>(
    std::initializer_list<T>{
        {{1, 1}, {1, 1}},
        {{1, 1}, {1, 1}}});

If push_back() is acceptable,

auto data=std::make_shared<std::vector<std::vector<std::vector<structure name>>>();
data->push_back({{1,1},{1,1}});
data->push_back({{1,1},{1,1}});

2022-12-22 04:07

If you have any answers or tips

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