How to insert and retrive an object without default ctor from container?

Hi,

I have a third party class object, CPP_OBJECT that i save in std container.
for example; i want to do the following.

std::map<std::string, CPP_OBJECT> mymap;
mymap["test"]= myobj;

mymap.insert["test",myobject];//This doesn't work!!


Now that I have created the CPP_OBJECT and save it to the map.

i want to retrieve the CPP_OBJECT from the map using a std::string ID later.

CPP_OBJECT l_object = mymap["test"];
apparent i can't do as ablve as the CPP_OBJECT does't have a default ctor.

CPP_OBJECT *l_object = &mymap["test"]; //this result in error "no default constructor available" in CPP_OBJECT,

Can anyone help me on this??

The operator[] of std::map creates an object (using the default constructor) if none is found at the given key. Since this is undesirable here, use the find() member function of std::map instead.

i tried the following:

Code:

---


mymap["test"]=mycppobj;

std::map<std::string,CPP_OBJECT>::iterator it=mymap.find("test");
std::pair<std::string,CPP_OBJECT> pair=*it;
CPP_OBJECT* t=pair.second(); //i still getting error : call of an object wihtout appropriate operator() or conversion functions to pointer-to-function type...

---

could you show me a simple working codes?

It should be something like:

Code:

---

std::map<std::string,CPP_OBJECT>::iterator it = mymap.find("test");
if (it != mymap.end())
{
    std::cout << *it << std::endl;
}

---

Quote:

---

Originally Posted by mce

could you show me a simple working codes?

---

There are thousands of examples in books, on the Internet, etc. If you're going to use the container classes, you should have reference material ready to use instead of guessing what the code should be:

http://www.cplusplus.com/reference/stl/map/find/

Regards,

Paul McKenzie

Quote:

---

Originally Posted by mce

i tried the following:

Code:

---


mymap["test"]=mycppobj;

std::map<std::string,CPP_OBJECT>::iterator it=mymap.find("test");
std::pair<std::string,CPP_OBJECT> pair=*it;
CPP_OBJECT* t=pair.second(); //i still getting error : call of an object wihtout appropriate operator() or conversion functions to pointer-to-function type...

---

could you show me a simple working codes?

---

Almost right, but "second" is just a struct member variable, not a function, so it should be:

Code:

---

std::map<std::string,CPP_OBJECT>::iterator it=mymap.find("test");
std::pair<std::string,CPP_OBJECT> pair=*it;
CPP_OBJECT* t=pair.second;//No parenthesis here

---

----

Quote:

---

Originally Posted by laserlight

It should be something like:

Code:

---

std::map<std::string,CPP_OBJECT>::iterator it = mymap.find("test");
if (it != mymap.end())
{
    std::cout << *it << std::endl;
}

---

---

That won't work, "it" is an iterator to a key-value pair, that isn't streamable. it should be (if you wanted to print the pair):

Code:

---

std::map<std::string,CPP_OBJECT>::iterator it = mymap.find("test");
if (it != mymap.end())
{
    std::cout << it->first << " " << it->second << std::endl;
}

---

Quote:

---

Originally Posted by monarch_dodra

That won't work, "it" is an iterator to a key-value pair, that isn't streamable. it should be (if you wanted to print the pair):

---

Yeah, my bad, I didn't test.