• local class
  在一個函式裡面宣告的類從屬於那個函式。比如說

void fun() {
    class base {
    private:
    public:
    };
}

local class 僅僅能夠在函式內部宣告物件

void fun() {
    class base {
    private:
        int i;
    public:
        base() { cout << "1" << endl; }
        void print() {
            cout << "2"
 
 << endl;
        }
    };
    base a;
    a.print();
}
int main() {
    base a;
    return 0;
}

local class 裡面的函式僅僅能夠在函式內部定義

void fun(){
    class base {
    private:
        int i;
    public:
        base() { cout << "1" << endl; }
        void print() { 
            cout << "2"
 
 << endl;
        }
    };
    base a;
    a.print();
}
int main() {
    fun();
    return 0;
}

void fun() {
    class base {
    private:
        int i;
    public:
        base() { cout << "1" << endl; }
        void print();
    };
    void base::print() {
        cout << "2"
 
 << endl;
    }
    base a;
    a.print();
}
int main() {
    fun();
    return 0;
}

區域性類不能定義靜態變數，但可以定義靜態函式

void fun() {
    class base {
    private:
        int i;
    public:
        static int m;
        void print() {
            cout << "2" << endl;
        }
    };
    base a;
    a.print();
}

static int i2;
void fun() {
    class base {
    private:
        int i;
    public:
        static void print() {
            i2++;
            cout << i2 << endl;
        }
    };
    base a;
    a.print();
}
int main() {
    i2++;
    fun();
    return 0;
}

區域性類僅僅能夠訪問本函式裡或全域性靜態變數或者列舉量

void fun() {
    static int i2;
    enum tem
    {
        x=0,y=0
    };
    class base {
    private:
        int i;
    public:
        static void print() {
            cout << "i2=" <<i2 << endl;
            cout << "x=" << x << endl;
        }
    };
    base a;
    a.print();
}
int main() {
    //i2++;
    fun();
    return 0;
}

void fun() {
    int x;
    class base {
    private:
        int i;
    public:
        void print() {
            cout << "x=" << x << endl;
        }
    };
    base a;
    a.print();
}

區域性變數可以訪問全域性變數，全域性函式，還能夠訪問函式內部其他類

int x=2;
void fun() {

    class base1 {
    private:

    public:int i=1;
        void print() {
            cout << "x=" << x << endl;
        }
    };
    class base2 :public base1{
    private:
        int i;
    public:
        void print() {
            cout << "base::i =" << base1::i << endl;
            cout << "x=" << x << endl;
        }
    };
    base2 a;
    a.print();
}
int main() {
    //i2++;
    fun();
    return 0;
}

• nested class

nested class是指在一個已經存在的類中定義的類，假設在A中定義了B，那麼B就是nested class。
這其中，有如下規則：
B可以改變A成員值；
A不可以改變B成員值。

B可以改變A成員值

class base1 {
private:
    int i;
    class base2 {
    private:
        int i2;
    public:
        base2(int i1) :i2(i1) {}
        void print(base1 *s) {
            cout << "---" << s->i << endl;
        }
    };
public:
    base1(int i1) :i(i1) {}
    void print() {
        cout << "---" << i << endl;
    }
};

A不可以改變B成員值

class base3{
private:
    int i;
    class base2 {
    private:
        int i2;
    public:
        base2(int i1) :i2(i1) {}
    };
public:
    base3(int i1) :i(i1) {}
    void print(base2 *s) {
        cout << "---" << s->i2 << endl;
    }
};