xtd::call_once Struct Reference

Definition

The xtd::call_once struct can be used to execute a routine exactly once. This can be used to initialise data in a thread-safe way.

Namespace

xtd

Library

xtd.core

Remarks

See also call_once_ keyword helper.

Examples

The following example shows how to use xtd::call_once struct.

#include <xtd/xtd>
 
using namespace xtd;
using namespace xtd::threading;
 
auto main() -> int {
  console::write_line("(main) begin");
  
  auto mre = manual_reset_event {};
  
  auto thread_proc = [&] {
    static auto cpt = 0;
    [[maybe_unused]] static auto __call_once__ = call_once {} + [&] {
      console::write_line("  (thread_proc) call once {} times", cpt + 1);
    };
    console::write_line("  (thread_proc) running {} times", ++cpt);
    if (cpt == 3) mre.set();
  };
  
  thread_pool::register_wait_for_single_object(mre, thread_proc, {}, 100, false);
  
  mre.wait_one();
  
  thread::join_all();
  console::write_line("(main) end");
}
 
// This code produces the following output :
//
// (main) begin
//   (thread_proc) call once 1 times
//   (thread_proc) running 1 times
//   (thread_proc) running 2 times
//   (thread_proc) running 3 times
// (main) end

Examples

call_once2.cpp.

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The documentation for this struct was generated from the following file:

• xtd.core/include/xtd/call_once.h