lock::operator bool

运算符用于 lock 一个条件表达式。

operator bool();

返回值

true ，如果锁被保留时，否则 false 。

备注

比 bool 安全的此运算符实际转换为 _detail_class::_safe_bool ，因为它不能转换为整型。

示例

此示例使用类的一个实例在多个线程中。类使用在自身的锁确保对其内部数据的访问为每个线程都是一致的。主应用程序线程使用类的同一个实例的锁定期检查任何辅助线程是否仍然存在，并会退出，直到所有辅助线程完成他们的任务。

// msl_lock_op_bool.cpp
// compile with: /clr
#include <msclr/lock.h>

using namespace System;
using namespace System::Threading;
using namespace msclr;

ref class CounterClass {
private:
   int Counter;   

public:
   property int ThreadCount;

   // function called by multiple threads, use lock to keep Counter consistent
   // for each thread
   void UseCounter() {
      try {
         lock l(this); // wait infinitely

         Console::WriteLine("In thread {0}, Counter = {1}", Thread::CurrentThread->ManagedThreadId, 
            Counter);

         for (int i = 0; i < 10; i++) {
            Counter++;
            Thread::Sleep(10);
         }
         
         Console::WriteLine("In thread {0}, Counter = {1}", Thread::CurrentThread->ManagedThreadId, 
            Counter);

         Counter = 0;
         // lock is automatically released when it goes out of scope and its destructor is called
      }
      catch (...) {
         Console::WriteLine("Couldn't acquire lock!");
      }

      ThreadCount--;
   }
};

int main() {
   // create a few threads to contend for access to the shared data
   CounterClass^ cc = gcnew CounterClass;
   array<Thread^>^ tarr = gcnew array<Thread^>(5);
   ThreadStart^ startDelegate = gcnew ThreadStart(cc, &CounterClass::UseCounter);
   for (int i = 0; i < tarr->Length; i++) {
      tarr[i] = gcnew Thread(startDelegate);
      cc->ThreadCount++;
      tarr[i]->Start();
   }

   // keep our main thread alive until all worker threads have completed
   lock l(cc, lock_later); // don't lock now, just create the object
   while (true) {
      l.try_acquire(50); // try to acquire lock, don't throw an exception if can't
      if (l) { // use bool operator to check for lock
         if (0 == cc->ThreadCount) {
            Console::WriteLine("All threads completed.");
            break; // all threads are gone, exit while
         }
         else {
            Console::WriteLine("{0} threads exist, continue waiting...", cc->ThreadCount);
            l.release(); // some threads exist, let them do their work
         }
      }
   }
}

要求

头文件 <msclr \ lock.h>

命名空间 msclr

请参见

参考

lock::is_locked

其他资源

锁定成员