CODEWITHSUNDEEP
c++referencestltuples
saga
saga

Reputation: 2113

Getting reference to the elements of a tuple

Let's say I have a tuple containing types A, B and C:

std::tuple<A,B,C> t;

How can I extract a reference to one of it's elements, a mutable reference, so that I can modify it?

std::get returns a copy.

Upvotes: 1

Views: 892

Answers (1)

patatahooligan
patatahooligan

Reputation: 3321

Contrary to what you said in the OP, std::get returns a reference. In fact it even has an overload for tuple&& that returns a T&&. Your misunderstanding probably stems from the fact that you were using it in an expression that results in a copy. A notable example of this would be auto which is designed to not declare a reference by default. Take a look at the following code.

std::tuple<int, int> my_tuple;

// Declare an int whose value is copied from the first member of the tuple
auto my_int = get<0>(my_tuple);

// Get a reference to it instead
auto& my_int_ref = std::get<0>(my_tuple);
my_int_ref = 0;    // Assign 0 to the first element

// Direct use inside an expression also works.
std::get<0>(my_tuple) = 1;    // Assign 1 to the first element.

Upvotes: 4

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