C++ Brain Teasers: Exercise Your Mind/

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Discussion: Who’s Up First?

Discussion: Who’s Up First?

Execute the code to understand the output and gain insights into constructors.

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Run the code

Now, it’s time to execute the code and observe the output.

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#include <iostream>
struct Resource
{
    Resource()
    {
        std::cout << "Resource constructed\n";
    }
};
struct Consumer
{
    Consumer(const Resource &resource)
    {
        std::cout << "Consumer constructed\n";
    }
};
struct Job
{
    Job() : resource_{}, consumer_{resource_} {}
    Consumer consumer_;
    Resource resource_;
};
int main() 
{
    Job job;
}

Understanding the output

The Job class has two members, consumer_ and resource_, declared in that order. However, in the constructor’s member initializer list (the : resource_{}, consumer_{resource_} part), they are initialized in the opposite order. In which order are they actually initialized?

Member initialization in C++

C++ always initializes members in the order they are declared in the class, not in the order they are listed in the constructor’s member ...