etl/docs/patterns/singleton-base.md

title
singleton_base

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Allows creation of a singleton base class.

etl::singleton_base<typename T>

T The type to use as a singleton.

The class derived derived from this must call the constructor with the instance of itself.
Multiple calls to the constructor will result in an etl::singleton_base_already_created assertion.

Before the constructor Is called, the singleton is in the invalid state.

See also etl::singleton

Static functions

static T& instance()

Returns a reference to the one instance of T.
Asserts an etl::singleton_base_not_created if the instance has not been attached.

---

static bool is_valid()

Returns true if the instance is has been attached, otherwise false.

Example

class MyType : public etl::singleton_base<MyType>
{
 MyType()
   : etl::singleton_base<MyType>(*this)
  {
  }
};

bool is_valid;
is_valid = MyType::is_valid();   // true

MyType& mt = MyType::instance(); // Get the instance