根据结构成员数据从向量返回结构项的函数

Question

Im very new to c++ so I'm not very familiar with how lambda functions work here. I want to see if the vector 'problems' contains a struct item with a particular member value equal to 'animalProblemNumber'. I then want return the entire struct item. Below is the 'for-loop version' of what I'm trying to achieve.

I also have a function called 'checkProblem' to see if the 'Problem item' exists in the first place. Can I achieve both of these in the one function?

Thank you to who ever can help me.

Problem getProblem(int animalProblemNumber, std::vector<Problem>      problems){
for(Problem p: problems){
    if(p.treatment == animalProblemNumber){
        return p;
    }
}

}

bool checkProblem(int animalProblemNumber, std::vector<Problem> problems){    //change this to lambda 
for(Problem p: problems){
    if(p.treatment == animalProblemNumber){
        return true;
    }
}
return false;
}

Answer 1

1. The return type of getProblem() will be a problem, no pun intended, if the vector does not contain at least one matching item. It will be better to return an iterator.

2. Change the input to getProblem() a const& so that the retured iterator is valid when the function returns.

3. After that, you can use getProblem() to implement checkProblem() .j

4. checkProblem() can also be changed to accept a const& although it is strictly not necessary.

std::vector<Problem>::const_iterator getProblem(int animalProblemNumber,
                                                std::vector<Problem> const& problems)
{
    return std::find_if(problems.begin(), problems.end(),
                        [animalProblemNumber](Problem const& item)
                        { return item.treatment == animalProblemNumber; });
}

and

bool checkProblem(int animalProblemNumber, std::vector<Problem> const& problems)
{
   return (getProblem(animalProblemNumber, problems) != problems.end());
}