google::cloud::spanner::TupleStream< Tuple > Class Template Reference

A TupleStream<Tuple> defines a range that parses Tuple objects from the given range of RowStreamIterators. More...

#include <google/cloud/spanner/row.h>

Public Types
using	iterator = TupleStreamIterator< Tuple >

Public Member Functions
iterator	begin () const
iterator	end () const

Friends
template<typename T , typename RowRange >
TupleStream< T >	StreamOf (RowRange &&range)
	A factory that creates a TupleStream<Tuple> by wrapping the given range. More...

Detailed Description

template<typename Tuple>
class google::cloud::spanner::TupleStream< Tuple >

A TupleStream<Tuple> defines a range that parses Tuple objects from the given range of RowStreamIterators.

Users create instances using the StreamOf<T>(range) non-member factory function (defined below). The following is a typical usage of this class in a range-for loop.

auto row_range = ...
using RowType = std::tuple<std::int64_t, std::string, bool>;
for (auto const& row : StreamOf<RowType>(row_range)) {
  if (!row) {
    // Handle error;
  }
  std::int64_t x = std::get<0>(*row);
  ...
}

Note

The term "stream" in this name refers to the general nature of the data source, and is not intended to suggest any similarity to C++'s I/O streams library. Syntactically, this class is a "range" defined by two "iterator" objects of type TupleStreamIterator<Tuple>.

Template Parameters

Tuple

the std::tuple<...> to parse each Row into.

Member Typedef Documentation

iterator

template<typename Tuple >

using google::cloud::spanner::TupleStream< Tuple >::iterator = TupleStreamIterator<Tuple>

Member Function Documentation

begin()

template<typename Tuple >

iterator google::cloud::spanner::TupleStream< Tuple >::begin ( ) const

inline

end()

template<typename Tuple >

iterator google::cloud::spanner::TupleStream< Tuple >::end ( ) const

inline

Friends And Related Function Documentation

StreamOf

template<typename Tuple >

template<typename T , typename RowRange >

TupleStream< T > StreamOf ( RowRange &&  range )

friend

A factory that creates a TupleStream<Tuple> by wrapping the given range.

The RowRange must be a range defined by RowStreamIterator objects.

void StreamOf(google::cloud::spanner::Client client) {
  namespace spanner = ::google::cloud::spanner;
 
  std::cout << "Querying the Singers table:\n";
  auto query = client.ExecuteQuery(spanner::SqlStatement(
      "SELECT SingerId, FirstName, LastName FROM Singers"));
  using RowType = std::tuple<std::int64_t, std::string, std::string>;
 
  for (auto& row : spanner::StreamOf<RowType>(query)) {
    if (!row) throw std::move(row).status();
    std::cout << "  SingerId: " << std::get<0>(*row) << "\n"
              << "  FirstName: " << std::get<1>(*row) << "\n"
              << "  LastName: " << std::get<2>(*row) << "\n";
  }
  std::cout << "end of results\n";
}

Note

Ownership of the range is not transferred, so it must outlive the returned TupleStream.

Template Parameters

RowRange

must be a range defined by RowStreamIterators.