Can't add elements of a struct type to vector?

Question

I'm trying to add two values into a vector of a custom type, without creating a variable of that type.

typedef struct duo{
    int uniqueID; 
    double data; 
};

vector<duo> myVector;
myVector.push_back({1,1.0});

But it won't allow it??

The only way I can get it to work is if I create the variable, but feels tedious...

vector<duo> myVector;
duo temp = {1,1.0};
myVector.push_back(temp);

Also... why can't I do this?

duo temp;
temp = {1,1.0};

but I can do this:

duo temp = {1,1.0};

???

Your code should compile if you're using a C++11 compiler. And that `typedef` is of no use. — Praetorian, Jan 27 '15 at 06:26
Please don't edit to include multiple questions. If you have a new question, ask it separately. — Masked Man, Jan 27 '15 at 06:47
http://stackoverflow.com/questions/4303513/push-back-vs-emplace-back useful link for this question — basav, Jan 27 '15 at 07:22

score 2 · Answer 1 · answered Jan 27 '15 at 06:45

You can avoid creating the temporary object while building your vector using std::vector::emplace_back().

Below is the code sample.

class duo {
public:
    duo(int uniqueID_, double data_)
        : uniqueID(uniqueID_)
        , data(data_) {}

private:        
    int uniqueID; 
    double data; 
};


int main() {
    vector<duo> myVector;
    myVector.emplace_back(1, 1.0);
}

score 0 · Answer 2 · edited Jan 27 '15 at 07:10

0

If you are using a C++11 compiler, compile the .cpp file using g++ -std=c++11. Also, remove typedef from the definition of the struct duo.

Otherwise you can create a parameterized constructor for duo and then use the constructor for push_back the duo objects into the vector.

Code:

struct duo {
    int uniqueID; 
    double data; 
    duo(int _uniqueID, double _data) : uniqueID{_uniqueID}, data{_data} {}
};

vector<duo> myVector;
myVector.push_back(duo(1,1.0)); //This compiles.

Hope that helped.

edited Jan 27 '15 at 07:10

bolov

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answered Jan 27 '15 at 06:30

shauryachats

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If you are on Linux, open the Terminal; If on Windows, open Command Prompt. Reach to the directory where your .cpp file is present. Let the .cpp file name be x.cpp . So, write `g++ -std=c++11 x.cpp -o x` if on Linux **or** `g++ -std=c++11 x.cpp -o x.exe` if on Windows. You will have no errors in compilation then. – shauryachats Jan 27 '15 at 07:38

Can't add elements of a struct type to vector?

2 Answers2