Virtual base class (a little difficult)

Solving ambiguity

Inherited a member with the same name from multiple base classes ：
adopt
1. The class name is qualified
2. The same name is hidden
3.using sentence
To solve

Inherited multiple base classes , These multiple base classes have the same base class , At this time, use the virtual base class to solve

Go straight to the topic

1. The following description of virtual base classes , The wrong is （ ）.
A、 Statement “class B : virtual public A” Description class B Is a virtual base class
B、 When creating a derived class object , The constructor of the virtual base class is called only once
C、 Using virtual base classes can eliminate the ambiguity caused by multiple inheritance
D、 When creating a derived class object , First, call the constructor of the virtual base class

Think so , because A Is a class that has been used many times , So set it to virtual , so A Option A Is a virtual base class
Carry the rest on your back
When creating an object , Only the constructor of the most derived class calls the constructor of the virtual base class , Calls from other classes to the virtual base class constructor are ignored

2. The ways to solve the ambiguity problem are （ ）.
A、 Only scope operators can be used
B、 Use scope operators or assignment compatibility rules
C、 Use scope operators or virtual base classes
D、 Use virtual base classes or assignment compatibility rules

C

3. The construction order of multiple inheritance can be divided into the following 4 Step ：
(1) Constructors of all non virtual base classes are constructed in the order they are inherited ;
(2) Constructors of all virtual base classes are constructed in the order they are inherited ;
(3) Constructors for all child objects are constructed in the order they are declared ;
(4) The constructor body of the derived class itself ;
this 4 The correct sequence of the steps is （ ）.
A、(4)(3)(1)(2)
B、(2)(4)(3)(1)
C、(2)(1)(3)(4)
D、(3)(4)(1)(2)

C
First virtual base class , Then base class , Then sub objects , Then own members

4. What is wrong in the following statement is （ ）.
A、 Derived classes can use private The derived
B、 Access to base class members must be unambiguous
C、 The access ability of base class members remains unchanged in derived classes
D、 Assignment compatibility rules also apply to multiple inheritance

C
This C Only public Inherit without changing access , The rest become corresponding