C ++：如何检查具有特定属性的对象是否存在于集合中

Question

I have the following structure:

struct dependence {
    dependence() {}
    dependence(string CUid, LID sink, LID source, std::string var)
    : CUid(CUid), sink(sink), source(source), var(var) {}

    string CUid;

    LID sink = 0;
    LID source = 0;
    std::string var;
};

Now I want to insert objects of this structure in a set. I have objects with the same CUid but (important!) the other properties ( sink , source , var ) can differ. I want to prevent inserting objects with the same CUid in the set. So the only way I know, is to iterate through the set and check each object of the CUid . Is there a better way with less code to check for that?

Answer 1

You can use a custom comparator that defines the order in which your objects will be stored in the set.

struct cmp
{
    bool operator()(const dependence &a,const dependence &b) const
    {
        return a.CUid < b.Cuid;
    }
};

and then

std::set<dependence,cmp> myset;

Now if you try to insert objects with same CUid , only the first instance will go in myset .

EDIT:

Another way would be to overload < operator.

bool operator<(const dependence &a,const dependence &b)
{
    return (a.CUid<b.CUid);

}

and then

std::set<dependence> myset;