CODEWITHSUNDEEP
c++jsonvector
FlatAssembler
FlatAssembler

Reputation: 782

My C++ attempt to convert std::vector<std::string> to JSON doesn't compile

I am trying to port a program I've written in JavaScript to C++ to make it faster. In that program, I dealt somewhat with JSONs. So, I tried to make a method for converting a vector of strings into JSON:

#include <iostream>
#include <vector>
#include <string>

class std::vector<std::string> {
    public: std::string JSON();
};

std::string std::vector<std::string>::JSON() {
    std::string ret="[";
    if (this->size()==0) {
        ret+="]";
        return ret;
    }
    int currentSize=this->size();
    for (int i=0; i<currentSize; i++) {
        if (i!=currentSize-1)
            ret+="\""+this->operator[](i)+"\",";
        else
            ret+="\""+this->operator[](i)+"\"]";
    }
    return ret;
}

int main(int argc, char **argv) {
    std::vector<std::string> fieldOfStrings({"Hello","world","!"});
    std::cout <<fieldOfStrings.JSON() <<std::endl;
    return 0;
}

However, it doesn't compile:

/home/teo.samarzija/Documents/AECforWebAssembly/AECforWebAssembly.cpp:5:12: error: too few template-parameter-lists
 class std::vector<std::string> {
            ^
/home/teo.samarzija/Documents/AECforWebAssembly/AECforWebAssembly.cpp:9:13: error: specializing member 'std::vector<std::basic_string<char> >::JSON' requires 'template<>' syntax
 std::string std::vector<std::string>::JSON() {

What am I doing wrong? I am fairly new to C++.

Upvotes: 0

Views: 323

Answers (2)

Lu&#226;n Nguyễn
Lu&#226;n Nguyễn

Reputation: 64

First, the class std::vector<std::string> does not make sense. Second, a class is not necessary since you can just define a function similar to your member function that takes in std::vector<std::string> and return the json string.

For example:

#include <iostream>
#include <vector>
#include <string>

std::string JSON(std::vector<std::string> str) {
    std::string ret="[";
    if (str.size()==0) {
        ret+="]";
        return ret;
    }
    int currentSize=str.size();
    for (int i=0; i<currentSize; i++) {
        if (i!=currentSize-1)
            ret+="\""+str[i]+"\",";
        else
            ret+="\""+str[i]+"\"]";
    }
    return ret;
}

int main(int argc, char **argv) {
    std::vector<std::string> fieldOfStrings({"Hello","world","!"});
    std::cout <<JSON(fieldOfStrings) <<std::endl;
    return 0;
}

Upvotes: 1

stefan.gal
stefan.gal

Reputation: 312

As mentioned above the easiest way is a free function.

std::string JSON(std::vector<std::string>& vec) {
    std::string ret="[";
    if (vec.size()==0) {
        ret+="]";
        return ret;
    }
    int currentSize=vec.size();
    for (int i=0; i<currentSize; i++) {
        if (i!=currentSize-1)
            ret+="\""+vec[i]+"\",";
        else
            ret+="\""+vec[i]+"\"]";
    }
    return ret;
}

And call it like

std::cout << JSON(fieldOfStrings) <<std::endl;

Upvotes: 1

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