Learn the design mode from another perspective-singleton Mode

There can only be one belief.

The Singleton mode is as literal as it means: only one instance can be created. At first glance, think about how it is possible to create countless instances as long as it is a class. Let's take a look at how God makes himself unique.

① God can create everything, and everything cannot create God. The method is to hide the construction method of "God ".

Class God

{

PRIVATE:

God ();

~ God ();

}

② Who created God? He can only be himself now.

Class God

{

PRIVATE:

Static god * _ godinstance;

Protected:

God ();

~ God ();

Public:

Static god * godinstance ();

}

God * God: _ godinstance = 0;

God * God: godinstance ()

{

_ Godinstance = new god ();

Return _ godinstance;

}

③ The constructor is hidden to prevent god from being freely created by others.

Class God

{

PRIVATE:

Static god * _ godinstance = 0; // use static to make the Variable _ godinstance initial

// Only executed during the first class instantiation

PRIVATE:

God ();

~ God ();

Public:

Static god * godinstance ();

}

God * God: _ godinstance = 0;

God * God: godinstance ()

{

If (godinstance = 0)

{

_ Godinstance = new god ();

}

Return _ godinstance;

}

④ Believers can only declare the existence of God.

Int * Main (INT argc, char * argv [])

{

God * SGN = God: godinstance ();

}