Can't get var operator String() to compile

General JUCE discussion
1

According to the documentation, var has an overloaded operator String() function for constructing a String out of a var, but I get an “ambiguous call” error when I try to compile it.

    var v1 (1);
    int w1 (v1);   // operator int(): works fine
    DBG (w1);

    var v2 ("v2");
    String w2 (v2);   // operator String(): won't compile
    DBG (w2);

Am I missing something here?

Note that I am aware of the toString() method. I was looking to use the operator String() constructor method in a template.

2

It’s ambiguous because the String constructor can take a bunch of different types, and the var object can produce those types. How does the String constructor know which to use? you can easily just do String w2 (v2.toString());

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3

I can see the ambiguity, I’m just wondering why the constructor is there if it’s not working?

4

String has no constructor that takes in a var.

5

Why which constructor? the operator String() works when it is asked for a String. But, the String constructor does not know what type is being passed in (since var can be many types), so it can’t ask for a String.

6

As @Xenakios said, you’re not calling var::operator String()… you’re calling String::String(var) which isn’t defined.

The var::operator String() function allows a var object to be passed to a function that takes a String as an argument, without needing to cast or convert it first:

void print(String message)
{
    std::cout << message << std::endl;
}

int main()
{
    var v1(1);
    print(v1);

    var v2("v2");
    print(v2);

    return 0;
}

// Output:
// 1
// v2
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7

I see! That’s a subtlety which had escaped me. Thanks for clearing it up!

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