CODEWITHSUNDEEP
c++
badri
badri

Reputation: 627

Retrieving structure from vector of structs following a find_if

I have written this small program to search for a struct inside a vector of structs. After this line in the code below, how should I extract the element of the vector that matched. i.e. the structure and its contents.

        if (std::find_if(jobInfoVector.begin(), jobInfoVector.end(), pred) != jobInfoVector.end())

#include <iostream>
#include <vector>
#include <algorithm>
#include "boost/bind.hpp"

using namespace std;
struct jobInfo
{
        std::string jobToken;
        time_t startTime;
        time_t endTime;
};
typedef struct jobInfo JobInfo;

int main()
{
        std::vector<JobInfo> jobInfoVector;
        JobInfo j1 = {"rec1",1234,3456};
        JobInfo j2 = {"rec2",1244,3656};
        JobInfo j3 = {"rec3",1254,8456};

        jobInfoVector.push_back(j1);
        jobInfoVector.push_back(j2);
        jobInfoVector.push_back(j3);

        auto pred = [](const JobInfo &jobinfo) { return jobinfo.startTime == 1234; };

        if (std::find_if(jobInfoVector.begin(), jobInfoVector.end(), pred) != jobInfoVector.end())
        {
                cout << "got a match" << endl;
        }
        else
        {
                cout << "Did not get a match" << endl;
        }

        return 0;
}

Upvotes: 0

Views: 444

Answers (2)

songyuanyao
songyuanyao

Reputation: 173044

You just need keep the iterator returned from std::find_if, and use it later.

Return value
Iterator to the first element satisfying the condition or last if no such element is found.

E.g. you can apply If Statements with Initializer (since C++17):

if (auto it = std::find_if(jobInfoVector.begin(), jobInfoVector.end(), pred); it != jobInfoVector.end())
{
        cout << "got a match" << endl;
        // use it from here...
}
else
{
        cout << "Did not get a match" << endl;
}

Upvotes: 3

K.R.Park
K.R.Park

Reputation: 1149

You can save the result of the std::find_if() as an iterator, then dereference to extract its components. Like:

#include <iostream>
#include <vector>
#include <algorithm>
#include "boost/bind.hpp"

using namespace std;
struct jobInfo
{
        std::string jobToken;
        time_t startTime;
        time_t endTime;
};
typedef struct jobInfo JobInfo;

int main()
{
        std::vector<JobInfo> jobInfoVector;
        JobInfo j1 = {"rec1",1234,3456};
        JobInfo j2 = {"rec2",1244,3656};
        JobInfo j3 = {"rec3",1254,8456};

        jobInfoVector.push_back(j1);
        jobInfoVector.push_back(j2);
        jobInfoVector.push_back(j3);

        auto pred = [](const JobInfo &jobinfo) { return jobinfo.startTime == 1234; };
        auto it = std::find_if(jobInfoVector.begin(), jobInfoVector.end(), pred);
        if (it != jobInfoVector.end())
        {
                jobInfo& match = *it;
                cout << "got a match" << endl;
                //Do whatever job with match
        }
        else
        {
                cout << "Did not get a match" << endl;
        }

        return 0;
}

Upvotes: 1

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