How do you call the function call operator on a unique_ptr?

Question

If a class has a function call operator that returns a reference to a container (heavily redacted):

class client_connection { 

public:

    concurrent_queue<T>& operator()() { return client; }

    concurrent_queue<T> client;

};

And another class which has a member of

client_connection

:

class remote {

public:

    void get_version() {

        auto d = ... something to generate data ...

        client().push(d.begin(), d.end());

    }

...

client_connection client;

};

This works if

client

is constructed as part of the

remote

object. However if you pass ownership to

remote

via a

unique_ptr

how do you call the function call operator?

Upon changing the call to

client()->push(d.begin(), d.end());

the resulting error message suggests that the issue is because the push is on the

unique_ptr

, not the

client_connection

.

Using

.get()

is now working on the underlying object but without function call operator:

client.get()->push(m.begin(), m.end()); // error: ‘class client_connection<unsigned char>’ has no member named ‘push’

However trying various combinations to invoke the function call operator all fail. How do you call the function call operator on an object contained in a

unique_ptr

?

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Answer 1

You do it like this

client->operator()().push(m.begin(), m.end());

You need to actually call the operator because you have a pointer. Alternatively, dereference the unique pointer instead:

(*client)().push(m.begin(), m.end());

How do you call the function call operator on a unique_ptr?

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