CODEWITHSUNDEEP
c++classreference
Alex
Alex

Reputation: 2299

No viable conversion from 'Class *' to 'Class' C++

I feel like this should be simple but for whatever reason I can't get it to work.

I'm trying to create an instance of a class that can be passed into and edited directly by other functions.

For example:

main()
{
    ClassFoo foo = new ClassFoo();
    someFunction(foo);
}

void someFunction(ClassFoo& f)
{
    f.add("bar");
}

The problem is, when compiling, I end up with this error.

no viable conversion from 'ClassFoo *' to 'ClassFoo'
    ClassFoo foo = new ClassFoo();
             ^    ~~~~~~~~~~~~~~~

It also says that other candidate constructors are not viable, however in my ClassFoo class I do have a constructor that looks like this:

ClassFoo::ClassFoo()
{}

So how would I be able to accomplish editing the ClassFoo variable in functions?

Upvotes: 14

Views: 27842

Answers (2)

aruisdante
aruisdante

Reputation: 9085

C++ is not Java (or C# I suppose). You should never use the new keyword unless you know that you need to. And it returns a pointer to the newly created class, hence the error you get. Likely, the following would be sufficient:

Class foo;
someFunction(foo);

For a default constructed object, you shouldn't include the () if you're not using new, as this does something completely different (see the most vexing parse)

Upvotes: 19

Sly_TheKing
Sly_TheKing

Reputation: 528

You're probably used to C# or similar sintax..

However, in C++, there are big differences between these lines:

ClassFoo foo; //local variable at stack
ClassFoo *foo = new ClassFoo(); //local pointer to some memory at heap which is structured like ClassFoo

You probably wanted first line just to create local object. There are numerous tutorials that describe difference between heap and stack.. so check them out

Upvotes: 6

Related Questions